JP3402115B2 - Tone signal detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tone signal detector for detecting tone signals transmitted on a telephone line.

[0002]

2. Description of the Related Art FIG. 33 shows, for example, JP-A-63-2364.
FIG. 1 is a configuration diagram showing a conventional tone signal detector disclosed in Japanese Patent Laid-Open No. 60-61, in which 1 is a DFT for performing a discrete Fourier transform (hereinafter referred to as DFT) on an input signal to extract electric power W1 having a frequency component f1. An arithmetic unit 2 performs a DFT operation on the input signal to extract an electric power W2 having a frequency component f2.
The calculator 3 integrates the input signal to obtain the power Wb of the input signal.
The integrator 4 for calculating the power ratio W2 / W1 of the power W2 with respect to the power W1 and the power ratio Wb / W2 of the power Wb with respect to the power W2 are compared with predetermined threshold values a and b, respectively. It is a comparator that determines the presence or absence of a signal.

Next, the operation will be described. A signal transmitted using a telephone line may include a voice signal and the like in addition to a modem signal transmitted and received by a facsimile machine. Therefore, when a facsimile machine or the like transmits / receives a modem signal, it is necessary to detect a training signal appearing at the head of the modem signal and then execute processing such as demodulation in the subsequent stage. FIG. 34 is an explanatory diagram showing an example of the power spectrum of a signal transmitted using a telephone line. While the average power spectrum of voice is represented by the solid line in the figure, V.V. The power spectrum of the training signal of the 29 modem is represented by the dotted line in the figure. As can be seen from the figure, this training signal is 0.5 kHz.
z is substantially equivalent to a superposition of three tone signals having power components of respective frequencies of 1.7 kHz and 2.9 kHz.

As is clear from FIG. 34, in the vicinity of the frequency of 1 kHz, the power component of the voice signal is relatively large, whereas the power component of the tone signal does not exist. On the other hand, when the frequency is near 2.9 kHz, the power component of the tone signal is relatively large,
The feature is that the power component of the audio signal is small.

Therefore, the conventional tone signal detector detects a tone signal as follows by utilizing such characteristics.

First, the DFT calculator 1 performs a DFT operation on an input signal to extract electric power W1 having a frequency of 1 kHz from the electric power components in the frequency domain.

Further, the DFT calculator 2 executes the DFT calculation on the input signal and extracts the electric power W2 having a frequency of 2.9 kHz from the electric power components in the frequency domain.

The integrator 3 integrates the input signal,
The power Wb of the input signal is calculated. When the electric powers W1, W2 and Wb are obtained in this way, the comparator 4 obtains the electric power ratio W2 / W1 of the electric power W2 to the electric power W1 and the electric power ratio Wb / W2 of the electric power Wb to the electric power W2.

When the power ratio W2 / W1 is larger than the threshold value a and the power ratio Wb / W2 is smaller than the threshold value b, the comparator 4 determines that the input signal has the above-mentioned characteristics. Since it can be determined, it is determined that the tone signal has arrived, and a signal indicating that is output.

[0010]

In conventional telephone communication, for example, ringback tone (ringing tone), dial tone (dialing tone), busy tone (busy tone) and the like are used. Ringback tones are generally tone signals with amplitude modulation, and dial tones and busy tones are tone signals without amplitude modulation. As described above, tone signals used in telephone communication, for example, include tone signals with amplitude modulation and tone signals without amplitude modulation. Since the conventional tone signal detection has the configuration described above, it is possible to detect that a tone signal has been input for any of the ringback tone, dial tone, and busy tone signals. The ringback tone (amplitude modulated signal), dial tone, busy tone (non-amplitude modulated signal) could not be discriminated and detected. Therefore, it has been impossible to detect only a specific tone of the tone signals used in the prior art device for telephone calls, for example.

The present invention has been made to solve the above problems, and an object thereof is to obtain a tone signal detector for detecting a specific tone (for example, ringback tone) with a simple structure.

[0012]

A tone signal detector according to a first aspect of the present invention compares a signal strength calculating means for calculating the strength of an input signal with the output of the signal strength calculating means to a predetermined threshold value. The comparison means and the judgment means for judging the presence or absence of the amplitude-modulated tone signal based on the output of the comparison means are provided.

A tone signal detector according to a second aspect of the present invention comprises a signal strength calculating means for calculating the strength of an input signal, a high pass filter for removing a DC component of the output of the signal strength calculating means, and Comparing means for comparing the output of the high-pass filter with a predetermined threshold value, and judging means for judging the presence or absence of the amplitude-modulated tone signal based on the output of the comparing means.

A tone signal detector according to a third aspect of the present invention is a signal strength calculation means for calculating the strength of an input signal, a smoothing means for smoothing the output of the signal strength calculation means, and the signal strength calculation. Comparing means for comparing the output of the means with the output of the smoothing means, and judging means for judging the presence or absence of the amplitude-modulated tone signal based on the output of the comparing means.

According to a fourth aspect of the present invention, a tone signal detector comprises a signal strength calculating means for calculating the strength of an input signal, a first smoothing means for smoothing the output of the signal strength calculating means, and The second smoothing means for smoothing the output of the signal strength calculating means, the comparing means for comparing the output of the first smoothing means with the output of the second smoothing means, and the output of the comparing means. On the basis of this, a determination means for determining the presence or absence of the amplitude-modulated tone signal is provided.

A tone signal detector according to a fifth aspect of the present invention is a tone signal detector for calculating the intensity of an input signal, a peak value extracting unit for extracting the peak value of the signal intensity calculating unit, and the peak value. Threshold setting means for setting a threshold based on the output of the extracting means, comparing means for comparing the output of the signal strength calculating means with the threshold output by the threshold setting means, and amplitude modulation based on the output of the comparing means. It also comprises a determination means for determining the presence or absence of a tone signal.

A tone signal detector according to a sixth aspect of the present invention comprises frequency selecting means for selecting and passing only a predetermined frequency component of the input signal, and the signal strength calculating means outputs the frequency selecting means. Based on this, the intensity of the signal of the predetermined frequency component is calculated.

In the tone signal detector according to the invention of claim 7, the peak value extracting means is provided with a leak circuit.

In the tone signal detector according to the eighth aspect of the present invention, the threshold value setting means outputs the value obtained by multiplying the output of the peak value extracting means by a predetermined coefficient as the threshold value.

In the tone signal detector according to the invention of claim 9, the smoothing means is provided with a low pass filter.

According to a tenth aspect of the present invention, the tone signal detector has a low-pass filter in the first smoothing means and the second smoothing means.

According to the eleventh aspect of the present invention, the tone signal detector has a bandpass filter in the frequency selecting means.

According to the twelfth aspect of the present invention, the tone signal detector has a frequency selecting means including a DFT (discrete Fourier transform) calculating means.

According to the thirteenth aspect of the present invention, the tone signal detector is provided with a square value calculating circuit in the signal strength calculating means.

According to a fourteenth aspect of the present invention, the tone signal detector has an absolute value calculating circuit in the signal strength calculating means.

According to a fifteenth aspect of the present invention, the tone signal detector has a detection circuit in the signal strength calculating means.

According to the sixteenth aspect of the present invention, in the tone signal detector, the signal strength calculating means integrates the output of the square value calculating circuit, the absolute value calculating circuit or the detecting circuit.

In the tone signal detector according to the seventeenth aspect of the present invention, the signal strength calculating means smooths the output of the square value calculating circuit, the absolute value calculating circuit or the detecting circuit.

In the tone signal detector according to the eighteenth aspect of the present invention, the signal strength calculating means includes a moving average circuit.

In the tone signal detector according to the nineteenth aspect of the present invention, the comparison means has a hysteresis characteristic in the comparison.

According to the twentieth aspect of the present invention, in the tone signal detector, the determining means makes the determination based on the frequency at which the change point of the output of the comparing means occurs.

In the tone signal detector according to the twenty-first aspect of the invention, the judging means makes the judgment based on the time interval at which the change point of the output of the comparing means occurs.

In the tone signal detector according to the twenty-second aspect of the present invention, the determination means makes the determination based on an average time interval at which a change point of the output of the comparison means occurs.

[0034]

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1. FIG. 1 is a block diagram showing an embodiment of a tone signal detector according to the present invention.
00 is frequency selecting means for selecting and passing only a predetermined frequency component of the input signal, 101 is frequency selecting means 10
A signal strength calculating means for calculating the signal strength S of the input signal based on the output of 0; 102 a comparing means for comparing the signal strength S output by the signal strength calculating means 101 with a predetermined threshold;
Reference numeral 103 is a judging means for judging the presence or absence of the amplitude modulation tone based on the output of the comparing means 102.

Next, the operation will be described. The frequency selecting means 100 selects and passes only a predetermined frequency component of the input signal. More specifically, for example, a bandpass filter can be used as the frequency selection unit 100. The purpose of processing the input signal by the frequency selecting means 100 is to remove the noise component and perform the detection processing when the noise signal is mixed in other than the tone signal of the frequency of the detection target, and It is to be able to detect without being affected.

FIG. 2 is a block diagram showing an example of the detailed structure of the frequency selecting means 100. In FIG.
01, 202, 203 are adders, 210, 211, 21
2, 213 are delay elements, 220, 221, 222, 22
3, 224, 225, 226, 227, 228, 22
Reference numerals 9 and 230 are multipliers. Adders 200, 201, 2
02 and 203 add the input signals to the adder and output the added value. Delay elements 210, 211, 212,
213 delays the input signal to the delay element by a time equal to the sampling period. Multipliers 220, 221, 22
2, 223, 224, 225, 226, 227, 22
8, 229, and 230 are for the input signal to the multiplier,
Filter coefficients s0, b11, b21, a01,
a11, a21, b12, b22, a02, a12, a
22 is multiplied and the multiplication result is output. The frequency selection means 100 configured as described above operates as a bandpass filter by setting an appropriate filter coefficient. The characteristics of this band pass filter must be designed so that only the frequency components of the tone signal to be detected are passed and signals in other bands are blocked. For example, the carrier frequency of the tone signal to be detected is 400 Hz ± 20 H
z, the pass band of the band pass filter is, for example, 400 so that it covers the range of carrier frequencies.
It may be designed to have a frequency of ± 40 Hz. The following table shows an example of the coefficients of the band-pass filter designed in this way when the sampling frequency of the input signal is 8000 Hz.

[0037]

[Table 1]

The signal strength calculation means 101 calculates the signal strength S of the input signal based on the output of the frequency selection means 100. FIG. 3 is a block diagram showing an example of the detailed configuration of the signal strength calculation means 101. In the figure, 110 is a multiplier and 111 is an integrator. The multiplier 110 squares the output value of the frequency selection means 100 to calculate the power of the input signal and outputs the squared value. The integrator 111 adds the squared value output from the multiplier 110 by the number of n samples and outputs the added value in order to obtain information on the change in the power of the input signal due to the amplitude modulation. The value of n is preferably selected within a range that is sufficiently larger than the period of the carrier of the tone signal to be detected and sufficiently smaller than the period of amplitude modulation. With such a configuration, as the signal strength S, a value obtained by integrating the squared value of the output of the frequency selection unit 100 within the interval of the above n samples is obtained. The signal strength calculation means 101 uses the above n.
Each sample is used as one processing unit, and the signal strength S is calculated every time n samples are input, and the result is output. Hereinafter, the processing unit of the n samples will be referred to as a processing frame.

The comparing means 102 is the signal strength calculating means 101.
The signal strength S output by is compared with a predetermined threshold L1, and the comparison result is output. That is, the signal strength S is equal to the threshold L1.
If it is larger, the comparison means 102 outputs "1" as the comparison result, and otherwise, it outputs "0".

In the comparing means 102, the signal strength S
The value of the threshold L1 used for the comparison with is the characteristic of the amplitude-modulated tone signal to be detected, eg, the average power of the signal,
It must be determined based on the modulation factor in amplitude modulation.
In amplitude modulation, the amplitude of the carrier signal is changed by the modulation signal. FIG. 4 is an explanatory diagram for explaining the operation of amplitude modulation,
As shown in the figure, the carrier signal Ec · cos (ωc · t)
When the amplitude of is changed by the modulation signal Em · cos (ωm · t + ψm), a signal represented by the following equation is obtained as an amplitude-modulated tone signal.

[0041]

[Equation 1]

Here, k = Em / Ec is called a modulation factor. Expanding the above formula,

[0043]

[Equation 2]

Thus, in addition to the carrier component (component with frequency ωc), the lower sideband component (component with frequency ωc-ωm)
And the upper sideband component (the component whose frequency is ωc + ωm). From the above equation, the average power P of this amplitude-modulated tone signal is given by the following equation.

[0045]

[Equation 3]

On the other hand, when the value of n is selected within a range sufficiently smaller than the period of amplitude modulation, the signal strength calculation means 1
The maximum value of the signal strength S output by 01 is

[0047]

[Equation 4]

And the minimum value is

[0049]

[Equation 5]

It becomes In the comparison means 102, the value of the threshold value L1 used for comparison with the signal strength S needs to be selected within a range smaller than the maximum value and larger than the minimum value. That is,

[0051]

[Equation 6]

It is necessary to select within the range.

For example, when the average power of the amplitude-modulated tone signal to be detected is −10 dBm0 and the modulation factor in amplitude modulation is 70%, that is, k = 0.7, the above equation (6) is

[0054]

[Equation 7]

It is rewritten as From the above formula (7), the threshold value L1 is −21.4 dBm0 or more, −6.3 dB.
It is necessary to select within the range of m0 or less.

When a permissible error is recognized in the average power of the amplitude-modulated tone signal to be detected and the modulation degree in the amplitude modulation, the average power and the modulation degree are changed within the range of the permissible error. In this case, the threshold value L1 may be selected so that the equation (6) is satisfied for all combinations of the average power and the modulation factor within this range.

The judging means 103 judges the presence or absence of the amplitude modulation tone based on the output of the comparing means 102. FIG. 5 is a configuration diagram showing an example of a detailed configuration of the determination means 103,
In the figure, 120 is a change point detector, 121 is a timer,
122 is a counter and 123 is a comparator.

The change point detector 120 changes the output of the comparing means 102 from "0" to "1" or from "1" to "1".
When the change to 0 "is detected, the change point detection pulse signal indicating that the change is detected is output.

The timer 121 outputs a control pulse signal for indicating signal processing timing, which is repeated every predetermined period T.

The counter 122 counts the number of times the change point detector 120 outputs the change point detection pulse signal during the predetermined period T. That is, when the counter 122 first receives the control pulse signal from the timer 121, the counter 122 resets the internal count value to 0, and thereafter, every time the change point detection unit 120 receives the change point detection pulse signal, the internal count value is reset. Increase the count value by one. When the control pulse signal is received again from the timer 121, the internal count value is output to the comparator 123, and then the internal count value is reset to 0.

The comparator 123 compares the output value of the counter 122 with a predetermined threshold value L2, and when the output value of the counter 122 is larger than the threshold value L2, it is determined that there is amplitude modulation.
1 "is output, and if not, it is determined that there is no amplitude modulation and" 0 "is output. The value of the threshold value L2 is the modulation period of the amplitude modulation tone signal to be detected. That is, when a tone signal modulated with a modulation period Tm is input, the expected value of the number of times the change point detection pulse signal is output during the predetermined period T is ( 2T / Tm), on the other hand, when a tone signal that is not amplitude-modulated is input, the number of times the change point detection pulse signal is output during the predetermined period T is 0 or a value very close to 0. Therefore, it is necessary to set the threshold L2 to a value not less than 0 and not more than (2T / Tm). By setting the value of the threshold L2 in this way, a tone signal modulated at the modulation cycle Tm is input. Counter 1 2 of the output value is larger than the threshold value L2, whereas, if the tone signal is not amplitude-modulated is inputted, the output value of the counter 122 to become smaller than the threshold value L2, in the comparator 123, the counter 12
The presence or absence of amplitude modulation can be determined based on the result of comparison between the output value of 2 and the threshold value L2.

6 and 7 are explanatory views for explaining the operation of the tone signal detector according to this embodiment.
7A shows the output of each unit when a tone signal not amplitude-modulated is given as an input signal, and FIG. 7 shows the output of each unit when an amplitude-modulated tone signal is given as an input signal.

As shown in FIG. 6, when a tone signal which is not amplitude-modulated is applied to this tone signal detector,
The frequency selection means 100 removes the noise component mixed in this tone signal and passes only the tone signal of the frequency to be detected. The signal strength calculation means 101 calculates the signal strength S for the output of the frequency selection means 100. However, since the input tone signal is not amplitude-modulated, the signal strength S is the tone signal input. Maintain a certain size throughout the life. When the tone signal is input, the output of the comparing unit 102 changes from "0" to "1" because the signal strength S becomes larger than the threshold value L1, and thereafter, "1" while the tone signal is input. Keep the state of ". Therefore, the change point detection pulse is output once when the tone signal is input, but thereafter the change point detection pulse signal is not output. Therefore, when the output value of the counter 122 does not exceed 1, and the threshold L2 in the determination means 103 is set to 1, for example, this counter 12
Since the output value of 2 does not exceed the threshold value L2, the determination means 103
Outputs "0" (no amplitude modulation) as a detection result for the tone signal input which is not amplitude modulated.

Further, as shown in FIG. 7, when an amplitude-modulated tone signal is applied to this tone signal detector,
The frequency selection means 100 removes the noise component mixed in this tone signal and passes only the tone signal of the frequency to be detected. The signal strength calculation means 101 calculates the signal strength S with respect to the output of the frequency selection means 100. However, since the input tone signal is amplitude-modulated, the signal strength S is the input signal accompanying the amplitude modulation. Increases or decreases with changes in the power of. While the tone signal is being input, the signal strength S becomes larger or smaller than the threshold value L1. Therefore, the comparison means 102 has “0” and “1”.
Alternately, the change point detector 120 changes the output of the comparison means 102 from "0" to "1", or "1".
A change point detection pulse signal is output at the time of change from 1 "to" 0 ".
When 2 is set to 1, for example, the output value of the counter 122 exceeds the threshold L2, and the determination means 103 determines that the amplitude-modulated tone signal input is a detection result.
1 "(with amplitude modulation) is output.

With the above arrangement, after the input signal is processed by the frequency selecting means, the signal strength calculating means calculates the signal strength S, and the comparing means compares the signal strength S with a predetermined threshold value. By having the determination means make the determination based on the information of the change point of the comparison result, it is possible to determine the presence or absence of amplitude modulation of the tone signal.

Further, when a bandpass filter is used as the frequency selecting means, when a noise signal is mixed in other than the tone signal of the frequency to be detected, the noise component is removed and the detection processing is performed, whereby noise is removed. There is an effect that can be detected without being affected by.

Further, when the signal strength calculating means calculates the squared value, there is an effect that the power of the input signal can be accurately calculated.

Further, when the signal strength calculating means integrates the squared value, there is an effect that information on the change in the power of the input signal due to the amplitude modulation can be extracted.

Further, when the input signal is an unmodulated tone signal, the determination means makes the determination based on the frequency at which the change point of the output of the comparison means occurs, and this frequency is small, and the input signal is amplitude-modulated. In case of a tone signal, there is an effect that the presence or absence of amplitude modulation can be determined by using the property that this frequency increases.

Embodiment 2. FIG. 8 is a block diagram showing another embodiment of the tone signal detector according to the present invention,
In the figure, 100 is a frequency selecting means for selecting and passing only a predetermined frequency component of the input signal, 101 is a signal strength calculating means for calculating the signal strength S of the input signal based on the output of the frequency selecting means 100, and 105 is A high-pass filter that passes only the high-pass component of the signal strength S output from the signal-strength calculation means 101, 102 is a comparison means that compares the output of the high-pass filter 105 with a predetermined threshold value, 103
Is a judging means for judging the presence or absence of the amplitude modulation tone based on the output of the comparing means 102.

Next, the operation will be described. The operations of the frequency selecting means 100 and the signal strength calculating means 101 are the same as those in the first embodiment, and therefore their explanations are omitted.

The high-pass filter 105 passes only the high frequency component of the signal strength S output from the signal strength calculation means 101, removes the DC component from the value of the signal strength S, and sets the average level of the waveform to 0 level. The signal SH shifted to is output.

FIG. 9 is a block diagram showing an example of the detailed structure of the high-pass filter 105. In FIG.
201 is an adder, 210 and 211 are delay elements, 220,
221, 222, 223, 224, and 225 are multipliers. The adders 200 and 201 add the input signals to the adders and output the added value. Delay elements 210, 21
1 delays the input signal to the delay element by a time equal to the sampling period. Multipliers 220, 221, 222, 2
23, 224, and 225 are filter coefficients s0, b11, b21, and a0 for the input signal to the multiplier, respectively.
Multiply by 1, a11 and a21 and output the multiplication result. The characteristic of this high-pass filter is that the component of the signal strength S output from the signal strength calculation means 101, which increases or decreases the signal strength due to the amplitude modulation, is passed, and the DC component is removed from the value of the signal strength S. Need to be designed. For example, when the modulation frequency of the tone signal to be detected in amplitude modulation is 20 Hz, the cutoff frequency of the high-pass filter, that is, the lower limit frequency of the pass band is set to, for example, 10 Hz so that the lower limit frequency is lower than the modulation frequency. You can design it like this. The sampling frequency of the input signal is 80
An example of the coefficients of the high-pass filter designed in this way at 00 Hz is shown in the table below.

[0074]

[Table 2]

The comparison means 102 is a high-pass filter 105.
Is compared with a predetermined threshold L1H, and the comparison result is output. That is, when the output SH of the high pass filter 105 is larger than the threshold value L1H, the comparison means 102
Outputs "1" as the comparison result, and otherwise outputs "0". In this embodiment, as described above, the output S of the high pass filter 105 is
Since the average level of the waveform of H is shifted to the 0 level, the value of the threshold L1H may be set to, for example, the 0 level or a minute amount close to the 0 level.

The judging means 103 judges the presence or absence of the amplitude modulation tone based on the output of the comparing means 102. The operation of the determination means 103 is the same as that in the first embodiment.

10 and 11 are explanatory views for explaining the operation of the tone signal detector according to this embodiment.
FIG. 10 shows the output of each section when a tone signal that has not been amplitude-modulated is given as an input signal, and FIG. 11 shows the output of each section when an amplitude-modulated tone signal is given as an input signal. .

As shown in FIG. 10, when a tone signal that has not been amplitude-modulated is given to this tone signal detector, the frequency selecting means 100 removes the noise component mixed in this tone signal and detects the target of detection. Only the frequency tone signal is passed. The signal strength calculation means 101 calculates the signal strength S for the output of the frequency selection means 100. However, since the input tone signal is not amplitude-modulated, the signal strength S is the tone signal input. Maintain a certain size throughout the life. High pass filter 105
Removes the DC component of the signal strength S. Comparison means 102
When the threshold value L1H at is extremely small, which is very close to 0 level, the output SH of the high-pass filter 105 is larger than the threshold value L1H during the input of the tone signal. Continue to output 1 ”. Therefore, the change point detection pulse signal is not output while the tone signal is input. Therefore, the counter 122
Has an output value of 0, and the threshold L2 in the determination means 103 is
When, for example, is set to 1, the output value of the counter 122 does not exceed the threshold value L2, so that the determination means 103 detects "0" (amplitude modulation) for the tone signal input which is not amplitude modulated. Is output).

Further, as shown in FIG. 11, when an amplitude-modulated tone signal is given to this tone signal detector, the frequency selection means 100 removes the noise component mixed in this tone signal, and the detection target is detected. Only the tone signal of the frequency is passed. The signal strength calculation means 101 calculates the signal strength S with respect to the output of the frequency selection means 100. However, since the input tone signal is amplitude-modulated, the signal strength S is the input signal accompanying the amplitude modulation. Increases or decreases with changes in the power of. High pass filter 105
Removes the DC component of the signal strength S. Comparison means 102
When the threshold value L1H at is set to a very small amount of negative value that is very close to 0 level, the output SH of the high-pass filter 105 becomes larger than the threshold value L1H along with the amplitude modulation operation while the tone signal is being input. The comparison means 102 alternately outputs "0" and "1" because it becomes smaller or smaller, and the change point detector 120 changes the output of the comparison means 102 from "0" to "1". Or "1" to "0"
When it changes to, the change point detection pulse signal is output. Therefore, the threshold L2 in the determination means 103 is set to, for example, 1
When set to, the output value of this counter 122 is the threshold L
When the number exceeds 2, the determination means 103 outputs "1" (with amplitude modulation) as a detection result for this tone-modulated tone signal input.

With the above arrangement, after the input signal is processed by the frequency selecting means, the signal strength calculating means calculates the signal strength S, and the high-pass filter 105 removes the DC component from the signal strength S, The presence or absence of the amplitude modulation of the tone signal is determined by comparing the output SH of the high-pass filter 105 with a predetermined threshold value in the comparison means, and having the determination means make the determination based on the information of the change point of the comparison result. There is an effect that can be.

Third embodiment. FIG. 12 is a configuration diagram showing an embodiment of a tone signal detector according to the present invention.
In the figure, 100 is a frequency selecting means for selecting and passing only a predetermined frequency component of the input signal, 101 is a signal strength calculating means for calculating the signal strength S of the input signal based on the output of the frequency selecting means 100, and 106 is Smoothing means for smoothing the signal strength S output from the signal strength calculating means 101; 102 comparing means for comparing the signal strength S output from the signal strength calculating means 101 with the output of the smoothing means 106;
Reference numeral 103 is a judging means for judging the presence or absence of the amplitude modulation tone based on the output of the comparing means 102.

Next, the operation will be described. The operations of the frequency selecting means 100 and the signal strength calculating means 101 are the same as those in the first embodiment, and therefore their explanations are omitted.

The smoothing means 106 is the signal strength calculation means 10.
The signal strength S output by 1 is smoothed, and the smoothed output L1A
Output as.

More specifically, a low pass filter can be used as the smoothing means 106. When a low-pass filter is used as the smoothing means 106, the fluctuation component of the signal intensity S due to the amplitude modulation when a tone signal with amplitude modulation is input to this tone signal detector is removed, and the signal intensity S is removed. It is possible to obtain the average value of the as the smoothed output L1A.

When a low pass filter is used as the smoothing means 106, the configuration shown in FIG. 9 can be used.
Although FIG. 9 is used to describe the configuration of the high-pass filter in the second embodiment, it can be used as a low-pass filter by setting another appropriate filter coefficient in the same configuration. Operate. The characteristics of this low-pass filter must be designed so as to remove the fluctuation component of the signal strength S of the signal strength S output from the signal strength calculation means 101 due to the amplitude modulation. For example, the modulation frequency of amplitude modulation of the tone signal to be detected is 20.
In the case of Hz, the cutoff frequency of the low pass filter, that is, the upper limit frequency of the pass band may be designed to be lower than the modulation frequency, for example, 10 Hz. Sampling frequency of input signal is 8000Hz
In the case of, an example of the coefficient of the low-pass filter designed in this way is shown in the following table.

[0086]

[Table 3]

The comparing means 102 is the signal strength calculating means 101.
The signal strength S output from the output signal is compared with the smoothed output L1A output from the smoothing means 106, and the comparison result is output. That is, when the signal strength S is larger than the smoothed output L1A, the comparison means 102 outputs "1" as the comparison result, and otherwise outputs "0".

The judging means 103 judges the presence or absence of the amplitude modulation tone based on the output of the comparing means 102. The operation of the determination means 103 is the same as that in the first embodiment.

13 and 14 are explanatory views for explaining the operation of the tone signal detector according to this embodiment.
13 shows the output of each section when a tone signal that is not amplitude-modulated is given as an input signal, and FIG. 14 shows the output of each section when an amplitude-modulated tone signal is given as an input signal. .

As shown in FIG. 13, when a tone signal that has not been amplitude-modulated is given to this tone signal detector, the frequency selecting means 100 removes the noise component mixed in this tone signal, and detects the detection target. Only the frequency tone signal is passed. The signal strength calculation means 101 calculates the signal strength S for the output of the frequency selection means 100. However, since the input tone signal is not amplitude-modulated, the signal strength S is the tone signal input. Maintain a certain size throughout the life. The smoothing means 106 smoothes the signal strength S and outputs it as a smoothed output L1A. Since the signal strength S is larger than the smoothed output L1A during the input of the tone signal, the comparison means 102 continues to output "1". Therefore, the change point detection pulse signal is not output while the tone signal is input. Therefore, the output value of the counter 122 becomes 0, and the determination means 10
When the threshold value L2 in 3 is set to, for example, 1, the output value of the counter 122 does not exceed the threshold value L2, so that the determination unit 103 outputs "0" as the detection result for the tone signal input that is not amplitude-modulated. "(No amplitude modulation)
Is output.

Further, as shown in FIG. 14, when an amplitude-modulated tone signal is applied to this tone signal detector, the frequency selection means 100 removes the noise component mixed in this tone signal, and the detection target is detected. Only the tone signal of the frequency is passed. The signal strength calculation means 101 calculates the signal strength S with respect to the output of the frequency selection means 100. However, since the input tone signal is amplitude-modulated, the signal strength S is the input signal accompanying the amplitude modulation. Increases or decreases with changes in the power of. The smoothing means 106 smoothes the signal strength S, removes the fluctuation component of the signal strength S due to amplitude modulation, and smoothes the average value of the signal strength S by the smoothed output L.
Obtained as 1A. While the tone signal is being input, the signal strength S becomes larger or smaller than the smoothed output L1A due to the amplitude modulation operation, so the comparison means 1
02 alternately outputs "0" and "1", and the change point detector 1
Numeral 20 indicates “0” to “1” of the output of the comparing means 102
A change point detection pulse signal is output at the time of change to "0" or change from "1" to "0". Therefore, the determination means 1
When the threshold value L2 in 03 is set to, for example, 1, the output value of the counter 122 exceeds the threshold value L2, and the determination means 103 detects "1" (amplitude) as the detection result for the amplitude-modulated tone signal input. Output (with modulation).

According to the above construction, after the input signal is processed by the frequency selecting means, the signal strength S is calculated by the signal strength calculating means, and the signal strength S is smoothed by the smoothing means 106.
To obtain a smoothed output L1A, and the comparison means compares the signal strength S with the smoothed output L1A,
By making the determination means make the determination based on the information of the change point of the comparison result, there is an effect that the presence or absence of the amplitude modulation of the tone signal can be favorably determined regardless of the signal level of the input signal.

When a low-pass filter is used as the smoothing means, the fluctuation component of the signal intensity S accompanying amplitude modulation when a tone signal with amplitude modulation is input to this tone signal detector is removed. The average value of the signal strength S can be obtained as the smoothed output L1A.

Fourth Embodiment FIG. 15 is a configuration diagram showing an embodiment of a tone signal detector according to the present invention.
In the figure, 100 is a frequency selecting means for selecting and passing only a predetermined frequency component of the input signal, 101 is a signal strength calculating means for calculating the signal strength S of the input signal based on the output of the frequency selecting means 100, 106- Reference numeral 1 is a first smoothing means for smoothing the signal strength S output from the signal strength calculating means 101, and 106-2 is a signal strength calculating means 101.
Second smoothing means for smoothing the signal strength S output by
102 is a comparison means for comparing the output of the first smoothing means 106-1 with the output of the second smoothing means 106-2; 103
Is a judging means for judging the presence or absence of the amplitude modulation tone based on the output of the comparing means 102.

Next, the operation will be described. The operations of the frequency selecting means 100 and the signal strength calculating means 101 are the same as those in the first embodiment, and therefore their explanations are omitted.

The first smoothing means 106-1 smoothes the signal strength S output from the signal strength calculation means 101 and outputs it as a smoothed output SA.

More specifically, a low pass filter can be used as the first smoothing means 106-1.
When a low-pass filter is used as the first smoothing means 106-1, the signal from which the fluctuation component of the signal strength S is removed due to the influence of noise or the like that cannot be removed by the frequency selecting means 100 is used as the smoothing output SA. Obtainable.

When a low pass filter is used as the first smoothing means 106, the configuration shown in FIG. 9 can be used. The characteristic of this low-pass filter is that the fluctuation component due to the influence of noise or the like is removed from the signal strength S output from the signal strength calculation means 101, and the fluctuation component of the signal strength S due to amplitude modulation is not removed. Need to be designed. For example, when the modulation frequency of the tone signal to be detected in the amplitude modulation is 20 Hz, the cutoff frequency of the low-pass filter, that is, the upper limit frequency of the pass band is set to be higher than the modulation frequency, for example, 10
It may be designed to be 0 Hz. The following table shows an example of the coefficients of the low-pass filter designed in this way when the sampling frequency of the input signal is 8000 Hz.

[0099]

[Table 4]

The second smoothing means 106-2 smoothes the signal strength S output from the signal strength calculating means 101 and outputs it as a smoothed output L1A.

More specifically, a low pass filter can be used as the second smoothing means 106-2.
The cutoff frequency of the low-pass filter used in the second smoothing means 106-2 is the first smoothing means 106-
It is necessary to make it sufficiently lower than the cutoff frequency of the low-pass filter used for No. 1. Second smoothing means 106-2
When a low-pass filter is used as, the fluctuation component of the signal strength S due to the amplitude modulation when a tone signal with amplitude modulation is input to this tone signal detector is removed, and the average of the signal strength S is removed. The value can be obtained as the smoothed output L1A.

When a low-pass filter is used as the second smoothing means 106, the same designing method as in the third embodiment when a low-pass filter is used as the smoothing means can be applied. That is, in the configuration of FIG. 9, if the filter coefficient shown in Table 3 is used, the average value of the signal strength S can be obtained as the smoothed output L1A.

The comparison means 102 is the first smoothing means 106.
-1 outputs the smoothed output SA to the second smoothing means 10
6-2 is compared with the smoothed output L1A output, and the comparison result is output. That is, when the smoothed output SA is larger than the smoothed output L1A, the comparison means 102 outputs "1" as the comparison result, and otherwise outputs "0".

The judging means 103 judges the presence or absence of the amplitude modulation tone based on the output of the comparing means 102. The operation of the determination means 103 is the same as that in the first embodiment.

16 and 17 are explanatory views for explaining the operation of the tone signal detector according to this embodiment.
FIG. 16 shows the output of each section when a tone signal that is not amplitude-modulated is given as an input signal, and FIG. 17 shows the output of each section when a tone signal that is amplitude-modulated is given as an input signal. .

As shown in FIG. 16, when a tone signal that has not been amplitude-modulated is given to this tone signal detector, the frequency selecting means 100 removes the noise component mixed in this tone signal and detects Only the frequency tone signal is passed. The signal strength calculation means 101 calculates the signal strength S for the output of the frequency selection means 100. However, since the input tone signal is not amplitude-modulated, the signal strength S is the tone signal input. Maintain a certain size throughout the life. First smoothing means 106-
1 smoothes the signal strength S and outputs it as a smoothed output SA, and the second smoothing means 106-2 smoothes the signal strength S and outputs it as a smoothed output L1A. While the tone signal is being input, the smoothed output SA is the smoothed output L1A.
Since it is larger, the comparison means 102 continues to output "1". Therefore, the change point detection pulse signal is not output while the tone signal is input. Therefore, the output value of the counter 122 becomes 0, and when the threshold L2 in the determination means 103 is set to 1, for example, this counter 1
Since the output value of 22 does not exceed the threshold value L2, the determination means 10
3 outputs "0" (no amplitude modulation) as a detection result to the tone signal input which is not amplitude modulated.

Further, as shown in FIG. 17, when an amplitude-modulated tone signal is given to this tone signal detector, the frequency selection means 100 removes the noise component mixed in this tone signal, and the detection target is detected. Only the tone signal of the frequency is passed. The signal strength calculation means 101 calculates the signal strength S with respect to the output of the frequency selection means 100. However, since the input tone signal is amplitude-modulated, the signal strength S is the input signal accompanying the amplitude modulation. Increases or decreases with changes in the power of. First smoothing means 106
-1 smoothes the signal strength S, removes fluctuation components due to the influence of noise or the like of the signal strength S, and obtains a smoothed output SA.
The second smoothing means 106-2 smoothes the signal strength S, removes the fluctuation component of the signal strength S due to amplitude modulation, and obtains an average value of the signal strength S as the smoothed output L1A.
While the tone signal is being input, the smoothing output SA becomes larger or smaller than the smoothing output L1A due to the amplitude modulation operation, so the comparison means 102 is "0".
And "1" are output alternately, and the change point detector 120 checks the change when the output of the comparing means 102 changes from "0" to "1" or from "1" to "0". Output pulse signal. Therefore, when the threshold L2 in the determination means 103 is set to 1, for example, this counter 1
The output value of 22 exceeds the threshold value L2, and the determination means 103 outputs "1" (with amplitude modulation) as the detection result for the amplitude-modulated tone signal input.

According to the above construction, the input signal is processed by the frequency selecting means, the signal strength S is calculated by the signal strength calculating means, and the signal strength S is smoothed by the first smoothing means 106-1. To obtain the smoothed output SA, the signal strength S is smoothed in the second smoothing means 106-2 to obtain the smoothed output L1A, and the smoothed output SA is compared with the smoothed output L1A in the comparing means. ,
By making the determination means make the determination based on the information of the change point of the comparison result, there is an effect that the presence or absence of the amplitude modulation of the tone signal can be favorably determined regardless of the signal level of the input signal.

Further, when a low-pass filter is used as the first smoothing means, there is an effect that a fluctuation component due to the influence of noise of the signal strength S can be removed and a stable detection operation can be realized. .

When a low-pass filter is used as the second smoothing means, a variation component of the signal strength S accompanying amplitude modulation when a tone signal with amplitude modulation is input to this tone signal detector. Is removed, and the average value of the signal strength S can be obtained as the smoothed output L1A.

Embodiment 5. FIG. FIG. 18 is a configuration diagram showing an embodiment of a tone signal detector according to the present invention,
In the figure, 100 is a frequency selecting means for selecting and passing only a predetermined frequency component of the input signal, 101 is a signal strength calculating means for calculating the signal strength S of the input signal based on the output of the frequency selecting means 100, and 107 is Peak value extracting means for extracting the peak value of the signal strength S output from the signal strength calculating means 101, and 108 is a peak value extracting means 107.
102 for setting a threshold based on the output of
Is a comparing means for comparing the signal strength S output from the signal strength calculating means 101 with the output of the threshold setting means 108, and 103 is a judging means for judging the presence or absence of the amplitude modulation tone based on the output of the comparing means 102.

Next, the operation will be described. The operations of the frequency selecting means 100 and the signal strength calculating means 101 are the same as those in the first embodiment, and therefore their explanations are omitted.

The peak value extraction means 107 extracts the peak value of the signal strength S output from the signal strength calculation means 101 and outputs the peak value P.

FIG. 19 is a block diagram showing the detailed structure of the peak value extraction means 107. In the figure, 192 is a comparator, 193 is a selector, 194 is a delay buffer, and 195.
Is a multiplier.

The comparator 192 multiplies the signal strength S by the multiplier 19
When the signal strength S is larger than the output of the multiplier 195, "1" is output, and when it is not, "0"
Is output.

The selector 193 selects either the signal strength S or the output of the multiplier 195 based on the output of the comparator 192, and outputs the selected value. That is, when the output of the comparator 192 is "1", the value of the signal strength S is selected and output, and the output of the comparator 192 is "0".
, The output of the multiplier 195 is selected and output.
The output of the selector 193 is used as the peak value extraction means 107.
Is the peak value P output by.

The delay buffer 194 delays the output of the selector 193 by the time corresponding to the processing frame. Therefore, the output of the delay buffer 194 becomes the peak value P calculated and obtained in the previous processing frame.

The multiplier 195 multiplies the output of the delay buffer 194 by a predetermined coefficient L3. The value of this coefficient L3 is
It is desirable that the value be slightly smaller than 1.0.

By configuring the peak value extraction means 107 in this way, when the value of the signal strength S rises, the value of the signal strength S is calculated in the output of the multiplier 195, that is, in the previous processing frame. The obtained peak value P is added to the coefficient L
Since the value becomes larger than the value multiplied by 3, the selector 193 selects the value of the signal strength S and outputs the selected value as the signal strength P.

On the other hand, when the value of the signal strength S decreases, the value of the signal strength S is calculated from the output of the multiplier 195, that is, the value obtained by multiplying the peak value P obtained by the previous calculation by the coefficient L3. Becomes smaller, the selector 193 operates in the multiplier 19
The output of 5 is selected and the selected value is output as the signal strength P.

Therefore, by configuring the peak value extracting means 107 in this way, when the value of the signal strength S rises, the value of the peak value P immediately rises as the signal strength S rises, while When the value of the signal strength S is decreasing, the value of the peak value P operates so as to gently decrease at a predetermined rate determined by the value of the coefficient L3.
A leak circuit is realized.

The threshold value setting means 108 sets the threshold value LP based on the peak value P output from the peak value extracting means 107.

The threshold value setting means 108 is more specifically provided with a multiplier, and a predetermined coefficient (0 or more,
It is only necessary to multiply by 1) and output the multiplication result as a threshold value LP. Here, for example, if the predetermined coefficient is 0.
If it is set to 5, an average value of the signal strength S is approximately obtained as the threshold value LP.

The comparison means 102 is the signal strength calculation means 101.
The signal strength S outputted by the above is compared with the threshold LP outputted by the threshold setting means 108, and the comparison result is outputted. That is, when the signal strength S is larger than the threshold value LP, the comparison means 102 outputs "1" as the comparison result, and otherwise outputs "0".

The judging means 103 judges the presence or absence of the amplitude modulation tone based on the output of the comparing means 102. The operation of the determination means 103 is the same as that in the first embodiment.

20 and 21 are explanatory views for explaining the operation of the tone signal detector according to this embodiment.
20 shows the output of each section when a tone signal that is not amplitude-modulated is given as an input signal, and FIG. 21 shows the output of each section when an amplitude-modulated tone signal is given as an input signal. .

As shown in FIG. 20, when a tone signal that has not been amplitude-modulated is given to this tone signal detector, the frequency selection means 100 removes the noise component mixed in this tone signal and detects Only the frequency tone signal is passed. The signal strength calculation means 101 calculates the signal strength S for the output of the frequency selection means 100. However, since the input tone signal is not amplitude-modulated, the signal strength S is the tone signal input. Maintain a certain size throughout the life. Peak value extraction means 107
Extracts the peak value of the signal strength S and outputs it as the peak value P. The threshold setting means 108 multiplies the peak value P by a coefficient, for example, 0.5, and outputs the multiplication result as the threshold LP. Since the signal strength S is larger than the threshold value LP while the tone signal is being input, the comparison means 102 is
Therefore, the change point detection pulse signal is not output while the tone signal is input. Therefore, the output value of the counter 122 becomes 0, and the threshold value L2 in the determination means 103 is set to 1, for example. In this case, since the output value of the counter 122 does not exceed the threshold value L2, the determination means 103 outputs "0" (no amplitude modulation) as the detection result for the tone signal input that is not amplitude modulated.

Further, as shown in FIG. 21, when an amplitude-modulated tone signal is given to this tone signal detector, the frequency selecting means 100 removes the noise component mixed in this tone signal, and the detection object is detected. Only the tone signal of the frequency is passed. The signal strength calculation means 101 calculates the signal strength S with respect to the output of the frequency selection means 100. However, since the input tone signal is amplitude-modulated, the signal strength S is the input signal accompanying the amplitude modulation. Increases or decreases with changes in the power of. Peak value extraction means 107
Extracts the peak value of the signal strength S and outputs it as the peak value P. The threshold setting means 108 multiplies the peak value P by a coefficient, for example, 0.5, and outputs the multiplication result as the threshold LP. The value of this threshold LP is approximately the signal strength S
Is the average value of. While the tone signal is being input, the signal strength S becomes larger or smaller than the threshold value LP with the operation of the amplitude modulation, so the comparison means 10
2 alternately outputs "0" and "1", and the change point detector 12
0 outputs a change point detection pulse signal when the output of the comparison means 102 changes from "0" to "1" or from "1" to "0". Therefore, the determination means 10
When the threshold value L2 in 3 is set to 1, for example, the output value of the counter 122 exceeds the threshold value L2, and the determination means 1
03 is for this amplitude modulated tone signal input,
"1" (with amplitude modulation) is output as the detection result.

According to the above construction, after the input signal is processed by the frequency selecting means, the signal strength calculating means calculates the signal strength S, and the peak value extracting means 107 extracts the peak value P of the signal strength S. The threshold value setting means 108 determines the threshold value LP based on the peak value P, the comparison means compares the signal strength S with the threshold value LP, and the determination means makes the determination based on the information of the change point of the comparison result. There is an effect that it is possible to favorably determine the presence or absence of amplitude modulation of the tone signal regardless of the signal level of the input signal.

When a leak circuit is used as the peak value extraction means 107, when the value of the signal strength S rises, the value of the peak value P rapidly rises, while when the value of the signal strength S falls. In the above, there is an effect that the value of the peak value P operates so as to gradually fall, and the peak value P of the signal strength S can be extracted.

When the threshold value setting means 108 multiplies the peak value P by a predetermined coefficient to obtain the threshold value LP, the threshold value L
As P, an average value of the signal strength S is approximately obtained,
There is an effect that the threshold value LP that can be used for good detection independent of the signal level of the input signal can be obtained.

Sixth Embodiment In the first to fifth embodiments, if the S / N ratio of the input signal is sufficiently high, the frequency selecting means 100 is not always necessary, and the input signal is directly input to the signal strength calculating means 101 to obtain the signal strength. Even if the configuration is such that S is calculated,
Similar to Nos. 5 to 5, there is an effect that the presence or absence of amplitude modulation of the tone signal can be determined.

Seventh Embodiment In addition, in the above-described first to fifth embodiments, the case where the bandpass filter is used as the frequency selecting means has been described, but not limited to the bandpass filter, for example, a discrete Fourier transform (hereinafter referred to as DFT) calculating means is used. You may use.

FIG. 22 is a block diagram showing another embodiment of the tone signal detector according to the present invention. In FIG.
Is frequency selecting means, 101 is signal strength calculating means, 13
Reference numerals 1 and 132 are multipliers and 133 is an adder. Operations other than the frequency selection means 100 and the signal strength calculation means 101 are as follows.
Since it is the same as that of the first embodiment and so on, only the operations of the frequency selection means 100 and the signal strength calculation means 101 will be described.

The frequency selecting means 100 selects and passes only a predetermined frequency component of the input signal. More specifically, the frequency selecting means 100 is, for example, a DF.
T computing means can be used. This DFT operation means is a sequence of input signal samples x (0), x (1), ...
The DFT operation defined by the following equation is performed on x (n-1).

[0136]

[Equation 8]

In the equation (8), fi is the frequency of the tone signal to be detected, and fs is the sampling frequency.

When the frequency selecting means 100 performs the DFT operation as described above, it outputs the operation result to the signal strength calculating means 101. Since the operation result is usually a complex number, the real part of the operation result. The output is divided into R and the imaginary part Q.

The frequency selecting means 100 performs a DFT operation every time n samples are input and outputs the operation result. The method of selecting the value of n is the same as in the first embodiment, and it is desirable to select it within a range that is sufficiently larger than the carrier cycle of the tone signal to be detected and sufficiently smaller than the amplitude modulation cycle.

The signal strength calculation means 101 calculates the signal strength of the input signal based on the output of the frequency selection means 100. The multiplier 131 calculates the squared value of the real part R of the output of the frequency selection means 100, and the multiplier 132 calculates the squared value of the imaginary part Q of the output of the frequency selection means 100. The adder 133 adds the output of the multiplier 131 and the output of the multiplier 132. With this configuration, the sum of the squared values of the real number part R and the imaginary number part Q of the output of the frequency selection means 100 is obtained as the output of the signal strength calculation means 101.

With the above-described structure, as in the first to fifth embodiments, when a noise signal other than the tone signal of the frequency to be detected is mixed, the noise component is removed and the detection processing is performed. By doing so, there is an effect that detection can be performed without being affected by noise.

Eighth Embodiment Further, in the first to fifth embodiments described above, the signal strength calculating means calculates the square value, but not limited to the square value calculation, for example, the absolute value calculation may be performed.

FIG. 23 is a block diagram showing an example of the detailed structure of the signal strength calculation means 101. In FIG.
Is an absolute value circuit, and 141 is an integrator. Since the operation other than the signal strength calculation means 101 is the same as that of the first embodiment and so on, only the operation of the signal strength calculation means 101 will be described.

The absolute value circuit 140 comprises the frequency selecting means 10
Calculate the absolute value of the 0 output. FIG. 24 is an explanatory diagram showing the operation of the absolute value circuit 140. As shown in the figure, the output value of the absolute value circuit 140 is always zero or a positive value.

The integrator 141 adds the absolute values output by the absolute value circuit 140 by the number of n samples and outputs the added value.

According to this structure, the calculation processing of the power of the input signal performed by the signal strength calculating means 101 can be performed more easily than in the first to fifth embodiments.

Ninth Embodiment Further, in the above-described first to fifth embodiments, the case where the signal strength calculating means calculates the squared value is described, but not limited to the squared value calculation, for example, detection may be performed.

FIG. 25 is a block diagram showing an example of the detailed structure of the signal strength calculation means 101. In FIG.
Is a detection circuit, and 143 is an integrator. Since the operation other than the signal strength calculation means 101 is the same as that of the first embodiment and so on, only the operation of the signal strength calculation means 101 will be described.

The detection circuit 142 comprises the frequency selection means 100.
The detection processing is performed on the output of. Further, FIG. 26 is an explanatory diagram showing the operation of the detection circuit 142. As shown in the figure, when the input to the detection circuit 142 is a positive value,
The detection circuit 142 outputs the input value as it is, and outputs a zero level signal when the input to the detection circuit 142 is a negative value, and the output value of the detection circuit 142 is always zero or a positive value. Take

The integrator 143 adds the output values of the detection circuit 142 by the number of n samples and outputs the added value.

According to this structure, the calculation processing of the power of the input signal performed by the signal strength calculation means 101 can be performed more easily than in the first to fifth embodiments.

[Embodiment 10] In addition, the first embodiment
Alternatively, in 8 or 9, the case where the signal strength calculation means integrates the squared value, the absolute value, or the detection output has been described, but not limited to integration, for example, smoothing processing may be performed.

FIG. 27 is a block diagram showing an example of the detailed structure of the signal strength calculation means 101, in which 110 is shown.
Is a multiplier and 144 is a smoothing circuit. Since the operation other than the signal strength calculation means 101 is the same as that of the first embodiment and so on, only the operation of the signal strength calculation means 101 will be described.

The multiplier 110 calculates the square value of the output of the frequency selecting means 100. The smoothing circuit 144 performs smoothing by processing the squared value output from the multiplier 110 with a low pass filter.

According to this structure, the squared value is smoothed by the signal strength calculating means, so that the information on the change in the power of the input signal due to the amplitude modulation is obtained as in the first, eighth or ninth embodiment. Has the effect that can be extracted.

Eleventh Embodiment FIG. 28 is a block diagram showing an example of the detailed configuration of the signal strength calculation means 101. In the figure, 150 is an absolute value circuit, 151-1, 151-.
2, 151-3 are delay buffers, 152 is an adder, 15
3 is a multiplier. Since the operation other than the signal strength calculation means 101 is the same as that in the first to fifth embodiments, only the operation of the signal strength calculation means 101 will be described.

The absolute value circuit 150 includes the frequency selecting means 10
Calculate the absolute value of the 0 output.

Delay buffers 151-1, 151-2, 1
51-3 delays the output of the absolute value circuit 150. The delay time in each of the delay buffers 151-1, 151-2, 151-3 needs to be equal to the sampling frequency of the input signal.

The adder 152 outputs the output of the absolute value circuit 150 and the delay buffers 151-1, 151-2, 151-3.
Add the outputs of.

The multiplier 153 multiplies the output of the adder 152 by a predetermined coefficient P. In this embodiment, since the number of added samples in the adder 152 is 4, the coefficient P to be multiplied in the multiplier 153 is 0.25 which is the reciprocal of the number of added samples.

With this configuration, the frequency selecting means 1
A moving average value obtained by averaging the absolute value of the output value of 00 for a plurality of past samples is obtained as the signal strength S output from the signal strength calculation means 101, and the amplitude modulation is performed as in the first to fifth embodiments. There is an effect that it is possible to extract information regarding the change in the power of the input signal with the change.

Twelfth Embodiment FIG. 29 shows the comparison means 102.
It is a block diagram which shows an example of the detailed structure of FIG.
Reference numerals 62 and 163 are comparators, and 164 is a selector. Since the operation other than the comparing means 102 is the same as that of the first to fifth embodiments, only the operation of the comparing means 102 will be described.

The comparator 162 is a signal strength calculating means 101.
The calculated signal strength S of is compared with a predetermined threshold L11,
When the signal strength S is larger than the threshold L11, "1" is output as the comparison result, and when the signal strength S is not larger than the threshold L11, "0" is output.

Further, the comparator 163 compares the signal strength S calculated by the signal strength calculation means 101 with a predetermined threshold L12, and when the signal strength S is larger than the threshold L12, outputs "1" as the comparison result. If the signal strength S is not larger than the threshold value L12, "0" is output. In addition, this L
The value of 12 is larger than the value of L11.

The selector 164 selects and outputs the output of the comparator 162 or the output of the comparator 163. When the current output of the selector 164 is “0”, the selector 164 selects and outputs the output of the comparator 163. On the other hand, when the current output of the selector 164 is “1”, the selector 164 selects 164 operates to select and output the output of the comparator 162.

The values of the thresholds L11 and L12 used in the comparison with the signal strength S in the comparators 162 and 163 are the same as those described in the first embodiment.
It should be determined based on the characteristics of the amplitude-modulated tone signal to be detected, such as the average power of the signal and the modulation factor in amplitude modulation. That is, the comparators 162, 1
63, the threshold value L1 used for comparison with the signal strength S
The values of 1 and L12 must be selected within a range smaller than the maximum value and larger than the minimum value of the signal strength S output by the signal strength calculation means 101, that is,

[0167]

[Equation 9]

It is necessary to select within the range of.

For example, when the average power of the amplitude-modulated tone signal to be detected is -10 dBm0 and the modulation factor in amplitude modulation is 70%, that is, k = 0.7, the above equation (9) is

[0170]

[Equation 10]

It is rewritten as From the above equation (10),
The thresholds L11 and L12 need to be selected within the range of -21.4 dBm0 or more and -6.3 dBm0 or less.

If a permissible error is found in the average power of the amplitude-modulated tone signal to be detected and the modulation degree in the amplitude modulation, the average power and the modulation degree are changed within the range of the permissible error. In such a case, the thresholds L11 and L1 are set so as to satisfy the equation (9) for all combinations of the average power and the modulation factor within this range.
You can select 2.

FIG. 30 is an explanatory view for explaining the operation of the comparing means 102. The initial value of the output of the selector 164 is "0", and the initial value of the signal strength S is smaller than L11. To do. Therefore, in the initial state, the selector 164 selects the output of the comparator 163.

The value of the signal strength S increases, and first, the signal strength S
When the value of exceeds the threshold L11, the output of the comparator 162 is "
It changes from 0 "to" 1 "(time point shown in A of the figure). However, since the selector 164 selects the output of the comparator 163 at this time, the output of the selector 164 holds" 0 ". There is.

When the value of the signal strength S further rises, the value of the signal strength S exceeds the threshold value L12, and the output of the comparator 163 changes from "0" to "1" (time point shown in B of the figure).
Accordingly, the output of the selector 164 changes from "0" to "1".
After that, the selector 164 operates so as to select the output of the comparator 162.

Then, between C and D in the figure, the signal strength S
Becomes smaller than the threshold value L12 again, and the output of the comparator 163 is “0”. During this period, however, the selector 164 selects the output of the comparator 162.
The output of 4 holds "1".

After that, when the value of the signal strength S falls again and the value of the signal strength S becomes smaller than the threshold value L12, the comparator 1
The output of 63 changes from "1" to "0" (at the time indicated by E in the figure). However, since the selector 164 has selected the output of the comparator 162 at this time, the output of the selector 164 also holds "1" here.

When the value of the signal strength S further decreases, the value of the signal strength S becomes smaller than the threshold value L11, and the comparator 162
Output changes from "1" to "0" (at the point indicated by F in the figure). Along with this, the output of the selector 164 changes from “1” to “0”, and thereafter, the selector 164 operates as the comparator 1
Operates to select 63 outputs.

Then, between G and H in the figure, the signal strength S
Becomes larger than the threshold L11 again, and the output of the comparator 162 is "1". During this period, however, the selector 164 selects the output of the comparator 163.
The output of 4 holds "0".

According to this structure, when the signal strength S increases, the larger threshold value, that is, the threshold value L12 is used, and when the signal strength S decreases, the smaller threshold value, that is, the threshold value L11 is used for comparison. By carrying out the comparison, it is possible to have a hysteresis characteristic in the comparison, it is possible to remove the influence of a slight change in the signal intensity S near the threshold value, and it is possible to eliminate the adverse effect of noise or the like.

Thirteenth Embodiment In the first to fifth embodiments, the determination unit 103 makes the determination based on the frequency at which the change point of the output of the comparison unit 102 occurs. However, in the determination unit 103, the change point of the output of the comparison unit 102 is determined. The determination may be made based on the time interval that occurs.

FIG. 31 is a block diagram showing an example of the detailed configuration of the judging means 103. In the figure, 170 is a change point detector, 171 is a counter, 172 is a data holding circuit, 17
3, 174 is a comparator, 175 is an AND circuit, 176-
1, 176-2 is a delay buffer, and 178 is a determination unit. The operation other than the determining means 103 is the same as that of the first embodiment, etc., so only the operation of the determining means 103 will be described.

The change point detector 170 changes the output of the comparing means 102 from "0" to "1" or from "1" to "1".
When a change to 0 "is detected, a change point detection pulse signal indicating that the change has been detected is output.

The counter 171 is the change point detector 17 described above.
When the change point detection pulse signal is output from 0, the internal count value is reset to 0. After that, the counter 17
1 measures the time interval at which the change point occurs, so the internal count value is increased by 1 every unit time, and when the change point detector 170 outputs the change point detection pulse signal again, After outputting the internal count value at the time point to the data holding circuit 172, the internal count value is reset to 0. Therefore, the output value of the counter 171 represents the time interval at which the change point of the output of the comparison means 102 occurs.

The data holding circuit 172 receives the change point detection pulse signal from the change point detector 170,
The output value of the counter 171 is fetched, and this value is output to the comparator 1
Output to 73 and 174.

The comparator 173 compares the output value of the data holding circuit 172 with a predetermined threshold L21, and the data holding circuit 1
If the output value of 72 is larger than the threshold value L21, "1" is output, and if not, "0" is output.

The comparator 174 compares the output value of the data holding circuit 172 with a predetermined threshold L22, and the data holding circuit 1
If the output value of 72 is smaller than the threshold value L22, "1" is output, and if not, "0" is output. here,
The value of the threshold L22 is assumed to be larger than the value of the threshold L21.

The threshold L21 and the threshold L22 need to be determined based on the modulation frequency of the amplitude modulation of the amplitude-modulated tone signal to be detected. For example, if the modulation frequency of the amplitude-modulated tone signal to be detected is 20 Hz, the amplitude modulation cycle is 50 ms. Since the change point of the output of the comparison means 102 occurs twice during one cycle of this amplitude modulation, the time interval at which the change point of the output of the comparison means 102 occurs is 25 ms.
Becomes The threshold value L21 needs to be smaller than the time interval at which the change point of the output of the comparison means 102 occurs, and in this case, it may be set to 20 ms, for example. Also,
The threshold value L22 needs to be a value larger than the time interval at which the change point of the output of the comparison unit 102 occurs, and in this case, it may be set to 30 ms, for example.

The AND circuit 175 ANDs the output of the comparator 173 and the output of the comparator 174. That is, when the output of the comparator 173 is "1" and the output of the comparator 174 is "1", "1" is output, and otherwise, "0" is output. Therefore, the AND circuit 17
When the time interval at which the change point of the output of the comparison means 102 occurs is larger than the threshold L21 and smaller than the threshold L22, it is determined that there is amplitude modulation, and the output of 5 outputs "1", and the comparison means 102 If the time interval at which the change point of the output of 1 occurs is smaller than the threshold L21 or larger than the threshold L22, it is determined that there is no amplitude modulation and "0" is output.

The delay buffers 176-1 and 176-2 are
The output of the AND circuit 175 is delayed, and the AND circuit 175 is delayed.
The previous determination result of 1 is used as the output value of the delay buffer 176-1, and the determination result of the AND circuit 175 two times before is used as the output value of the delay buffer 176-2.

The determination section 178 finally determines the presence or absence of amplitude modulation based on the output of the AND circuit 175 and the outputs of the delay buffers 176-1 and 176-2. Judgment unit 178
More specifically, a logical product circuit can be used. In this case, when the determination results of the past three times output from the logical product circuit 175 are all “1” (with amplitude modulation), the determination unit The 178 finally judges that there is amplitude modulation and outputs "1", and otherwise judges that there is no amplitude modulation and outputs "1".
0 "is output.

According to this structure, the determination means 103 can determine the presence / absence of amplitude modulation based on the time interval at which the change point of the output of the comparison means 102 occurs.

Fourteenth Embodiment Although the determination unit 178 uses the AND circuit in the above embodiment,
For example, a majority circuit may be used instead of the logical product circuit. In this case, when the number of determinations as “1” (with amplitude modulation) is two or more among the past three determination results output from the AND circuit 175, the determination unit 178 finally determines that there is amplitude modulation. If it is once or less, it is determined that there is no amplitude modulation and "0" is output.

Fifteenth Embodiment In the first to fifth embodiments, the determination means 103 makes the determination based on the frequency at which the change point of the output of the comparison means 102 occurs, and in the thirteenth embodiment, the determination means 103 makes the comparison means. Although the determination is made based on the time interval at which the change point of the output of 102 occurs, the determination means 10
In 3, the determination may be made based on the average time interval at which the change point of the output of the comparison means 102 occurs.

FIG. 32 is a block diagram showing an example of the detailed configuration of the judging means 103. In the figure, 170 is a change point detector, 171 is a counter, 172 is a data holding circuit, and 18
0-1 and 180-2 are delay buffers, 182 is an average value circuit, 183 and 184 are comparators, and 185 is an AND circuit. The operation other than the determining means 103 is the same as that of the first embodiment, etc., so only the operation of the determining means 103 will be described.

Since the operations of the change point detector 170, the counter 171, and the data holding circuit 172 are the same as those in the thirteenth embodiment, their description will be omitted.

The delay buffers 180-1 and 180-2 are
The output of the data holding circuit 172 is delayed, the previous output value of the data holding circuit 172 is set as the output value of the delay buffer 180-1, and the output value of the data holding circuit 172 two times before is output of the delay buffer 180-2. And works like.

The average value circuit 182 is the data holding circuit 17
2. The average value of the outputs of the delay buffers 180-1 and 180-2 is calculated, and the average value calculation result is output. Therefore, the output of the average value circuit 182 is the average value of the past three times of the time interval at which the change point of the output of the comparison means 102 occurs.

The comparator 183 compares the output value of the average value circuit 182 with a predetermined threshold value L23, and outputs "1" when the output value of the average value circuit 182 is larger than the threshold value L23.
Otherwise, "0" is output.

The comparator 184 compares the output value of the average value circuit 182 with a predetermined threshold value L24, and outputs "1" when the output value of the average value circuit 182 is smaller than the threshold value L24.
Otherwise, "0" is output. Here, the threshold L2
The value of 4 is larger than the value of the threshold value L23.

The thresholds L23 and L24 need to be determined based on the modulation frequency of the amplitude modulation of the amplitude-modulated tone signal to be detected, as described in the thirteenth embodiment. For example, when the amplitude modulation tone frequency of the amplitude-modulated tone signal to be detected is 20 Hz, the time interval at which the output of the comparison unit 102 changes is 25 ms. The threshold value L23 needs to be smaller than the time interval at which the change point of the output of the comparison means 102 occurs, and in this case, it may be set to 23 ms, for example. Further, the threshold L24 is
The value must be larger than the time interval at which the change point of the output of the comparison means 102 occurs, and in this case, it is 27 m, for example.
It should be s.

The logical product circuit 185 takes the logical product of the output of the comparator 183 and the output of the comparator 184. That is, when the output of the comparator 183 is "1" and the output of the comparator 184 is "1", "1" is output, and otherwise, "0" is output. Therefore, the AND circuit 18
In the output of No. 5, the average time interval at which the change point of the output of the comparison unit 102 occurs is larger than the threshold L23 and the threshold L2.
If it is smaller than 4, it is determined that there is amplitude modulation, "1" is output, and the average time interval at which the change point of the output of the comparison means 102 occurs is smaller than the threshold L23 or the threshold L2.
If it is larger than 4, it is determined that there is no amplitude modulation and "0" is output.

According to this structure, the determination means 103 can determine the presence / absence of amplitude modulation based on the average time interval at which the change point of the output of the comparison means 102 occurs.

As described above, according to the present invention, a tone signal detector for detecting only a specific tone signal can be obtained by simply detecting the presence or absence of amplitude modulation.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a tone signal detector according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing frequency selecting means of the tone signal detector according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram showing a signal strength calculation means of the tone signal detector according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram illustrating an amplitude modulation operation.

FIG. 5 is a configuration diagram showing a judging means of the tone signal detector according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating an operation of the tone signal detector according to the first embodiment of the present invention.

FIG. 7 is an explanatory diagram illustrating an operation of the tone signal detector according to the first embodiment of the present invention.

FIG. 8 is a configuration diagram showing a tone signal detector according to a second embodiment of the present invention.

FIG. 9 is a configuration diagram showing a high-pass filter of the tone signal detector according to the second embodiment of the present invention.

FIG. 10 is an explanatory diagram illustrating an operation of the tone signal detector according to the second embodiment of the present invention.

FIG. 11 is an explanatory diagram illustrating an operation of the tone signal detector according to the second embodiment of the present invention.

FIG. 12 is a configuration diagram showing a tone signal detector according to a third embodiment of the present invention.

FIG. 13 is an explanatory diagram illustrating an operation of the tone signal detector according to the third embodiment of the present invention.

FIG. 14 is an explanatory diagram illustrating an operation of the tone signal detector according to the third embodiment of the present invention.

FIG. 15 is a configuration diagram showing a tone signal detector according to a fourth embodiment of the present invention.

FIG. 16 is an explanatory diagram illustrating an operation of the tone signal detector according to the fourth embodiment of the present invention.

FIG. 17 is an explanatory diagram illustrating an operation of the tone signal detector according to the fourth embodiment of the present invention.

FIG. 18 is a configuration diagram showing a tone signal detector according to a fifth embodiment of the present invention.

FIG. 19 is a configuration diagram showing peak value extraction means of a tone signal detector according to a fifth embodiment of the present invention.

FIG. 20 is an explanatory diagram illustrating an operation of the tone signal detector according to the fifth embodiment of the present invention.

FIG. 21 is an explanatory diagram illustrating an operation of the tone signal detector according to the fifth embodiment of the present invention.

FIG. 22 is a configuration diagram showing frequency selecting means and signal strength calculating means of the tone signal detector according to the seventh embodiment of the present invention.

FIG. 23 is a configuration diagram showing a signal strength calculating means of a tone signal detector according to an eighth embodiment of the present invention.

FIG. 24 is an explanatory diagram illustrating an operation of the tone signal detector according to the eighth embodiment of the present invention.

FIG. 25 is a configuration diagram showing a signal strength calculating means of a tone signal detector according to a ninth embodiment of the present invention.

FIG. 26 is an explanatory diagram illustrating an operation of the tone signal detector according to the ninth embodiment of the present invention.

FIG. 27 is a configuration diagram showing a signal strength calculation means of the tone signal detector according to the tenth embodiment of the present invention.

FIG. 28 is a configuration diagram showing a signal strength calculating means of a tone signal detector according to an eleventh embodiment of the present invention.

FIG. 29 is a configuration diagram showing a comparison means of the tone signal detector according to the twelfth embodiment of the present invention.

FIG. 30 is an explanatory diagram illustrating an operation of the tone signal detector according to the twelfth embodiment of the present invention.

FIG. 31 is a configuration diagram showing a judging means of a tone signal detector according to a thirteenth embodiment of the present invention.

FIG. 32 is a configuration diagram showing a judging means of the tone signal detector according to the fifteenth embodiment of the present invention.

FIG. 33 is a configuration diagram showing a conventional tone signal detector.

FIG. 34 is an explanatory diagram illustrating an operation of a conventional tone signal detector.

[Explanation of symbols]

100 frequency selection means 101 signal strength calculation means 102 comparison means 103 determination means 105 high pass filter 106 smoothing means 106-1 First smoothing means 106-2 Second smoothing means 107 peak value extraction means 108 threshold setting means

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-250961 (JP, A) JP-A-5-300551 (JP, A) JP-A-8-237696 (JP, A) JP-A-8- 265457 (JP, A) JP 63-236460 (JP, A) JP 63-236099 (JP, A) International Publication 95/020272 (WO, A1) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) H04Q 1/444

Claims (22)

(57) [Claims] 1. A signal strength calculating means for calculating the strength of an input signal, a comparing means for comparing the output of the signal strength calculating means with a predetermined threshold, and an amplitude-modulated tone based on the output of the comparing means. A tone signal detector comprising a determination means for determining the presence or absence of a signal. 2. A signal strength calculating means for calculating the strength of an input signal, a high-pass filter for removing a DC component of the output of the signal strength calculating means, and an output of the high-pass filter for comparison with a predetermined threshold value. The tone signal detector is characterized by comprising: a comparison means for performing the above-mentioned comparison; 3. A signal strength calculation means for calculating strength of an input signal, a smoothing means for smoothing an output of the signal strength calculation means, and an output of the signal strength calculation means with an output of the smoothing means. The tone signal detector is characterized by comprising: a comparison means for performing the above-mentioned comparison; 4. A signal strength calculation means for calculating the strength of an input signal, and a first smoothing means for smoothing the output of the signal strength calculation means.
Smoothing means, second smoothing means for smoothing the output of the signal strength calculating means, and comparing means for comparing the output of the first smoothing means with the output of the second smoothing means. ,
A tone signal detector comprising: a determination unit that determines the presence or absence of an amplitude-modulated tone signal based on the output of the comparison unit. 5. A signal strength calculation means for calculating the strength of an input signal, a peak value extraction means for extracting the peak value of the signal strength calculation means, and a threshold setting for setting a threshold value based on the output of the peak value extraction means. Means, comparing means for comparing the output of the signal strength calculating means with the threshold value output by the threshold value setting means, and determining means for determining the presence or absence of the amplitude-modulated tone signal based on the output of the comparing means. A tone signal detector characterized in that 6. A frequency selecting means for selecting and passing only a predetermined frequency component of the input signal, wherein the signal strength calculating means determines the strength of the signal of the predetermined frequency component based on the output of the frequency selecting means. The tone signal detector according to any one of claims 1 to 5 , which is calculated. 7. The tone signal detector according to claim 5, wherein the peak value extracting means includes a leak circuit. 8. The tone signal detector according to claim 5, wherein the threshold value setting means outputs a value obtained by multiplying the output of the peak value extracting means by a predetermined coefficient as a threshold value. 9. The tone signal detector according to claim 3, wherein the smoothing means includes a low pass filter. 10. The tone signal detector according to claim 4, wherein the first smoothing unit and the second smoothing unit include a low-pass filter. 11. The tone signal detector according to claim 6, wherein the frequency selection unit includes a bandpass filter. 12. The tone signal detector according to claim 6, wherein the frequency selection unit includes a DFT (Discrete Fourier Transform) calculation unit. Wherein said signal intensity calculating means, characterized in that it comprises a square value calculation circuit, claims 1 6 Neu
Tone signal detector according to Zureka. 14. The method of claim 13, wherein the signal strength calculation unit, characterized in that it comprises an absolute value calculation circuit, claims 1 to 6 Neu
Tone signal detector according to Zureka. 15. The signal intensity calculating means, characterized in that it comprises a detection circuit, the tone signal detector according to any <br/> of claims 1 to 6. 16. The signal intensity calculating means is characterized by integrating the output of the square value calculating circuit or the absolute value calculation circuit or the detection circuit, according to any one of claims 13 to 15 Tone signal detector. 17. The signal intensity calculating means, characterized by smoothing the output of the square value calculating circuit or the absolute value calculation circuit or the detection circuit, according to any one of claims 13 to 15 Tone signal detector. 18. The method of claim 17, wherein the signal strength calculation unit, characterized in that it comprises a moving average circuit, claims 1 6 Noise
A tone signal detector according to any one of the above. 19. The comparison means is characterized in that a hysteresis characteristic in comparison, the tone signal detector according to any of claims 1 to 6. 20. The method of claim 19, wherein determining means may determine on the basis of the frequency of the change point of the output of said comparator means occurs, the tone signal detector according to any of claims 1 to 6. 21. The determination means may determine on the basis of the time interval change point of the output results of said comparison means, a tone signal detector according to any of claims 1 to 6. 22. The determination unit may be determined based on the average time interval change point of the output of said comparator means occurs, the tone signal detector according to any of claims 1 to 6.