JP3472668B2 - Tone signal detection circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for detecting a tone signal used for a CTCSS or the like in a radio communication device. 2. Description of the Related Art Conventionally, a CTCS in a radio communication device has been used.
The detection of the presence of a tone signal used for S or the like uses an analog system using a dedicated IC that detects the level of the tone signal and determines whether the detected level exceeds a predetermined threshold. ing. For that purpose, it is necessary to detect whether or not a specific frequency component (tone signal) is included in the input signal by frequency analysis processing such as Fourier transform. In order to perform such a frequency analysis process, it is necessary to determine how much the frequency component of the tone signal is included in the input signal. As a technique, a fundamental frequency having the same frequency as the tone signal is generated. The correlation between a frequency and an input signal is obtained. The fundamental frequency for detecting the tone signal is at least T
Is used as a sinusoidal wave sin (2πt / T) or a cosine wave cos (2πt / T). In recent years, with the development of digital technology, a digital signal processor that directly converts an input signal into an analog signal and processes the digital signal by digital processing has been used for the purpose of reducing the size and cost of circuits and devices. Circuits are becoming mainstream. Also, for example, CTC in a wireless communication device
In SS, a plurality of tone signals are often used selectively, and therefore, a tone signal detection circuit is required to detect a plurality of tone signals. An example of a general tone signal detection circuit using a digital signal processor will be described below with reference to FIG. The circuit of FIG. 3 detects whether a predetermined tone signal is included in the input signal by converting the input signal into a frequency domain of a predetermined tone signal. First, the input signal is converted into a digital signal by the A / D converter 101 at a predetermined sampling frequency output from the sampling frequency output unit 105. The correlator 102 performs a correlation operation for each sampling period using both the converted digital signal and predetermined basic waveform data output from the basic waveform data output unit 103, so that the input signal is It is converted into the frequency domain of the predetermined tone signal. The signal subjected to the correlation operation is
The discrimination circuit 106 compares the signal with the threshold value. If the value does not exceed the threshold value, it is determined that the predetermined tone signal is not included in the input signal. If the value exceeds the threshold value, the predetermined tone signal is included in the input signal. Is determined. In this way, a predetermined tone signal is detected. The predetermined basic waveform data is obtained by reading a waveform data table for one cycle of a sine wave and a cosine wave stored in advance in a memory 104 in a basic waveform data output unit 103 in accordance with a reading step. It is generated by reading each time. At this time, the frequency at which the input signal is sampled and the frequency at which the waveform data is read from the memory 104 are set to constant frequencies regardless of the tone signal to be detected. As shown in FIG. 4, for the tone signals S1, S2, and S3 having different frequencies, since the angle of advance is different for each sampling cycle, the tone signals having different frequencies are provided as long as the sampling frequency is constant. The basic waveform data corresponding to each tone signal required for detection must be read in a reading step at a different angle for each tone signal. Since the reading step differs for each tone signal, it is necessary to store a tone signal and a reading step table indicating reading steps corresponding to the tone signal in a memory as shown in FIG. Note that the reading step table in FIG.
(/ Cycle 1 ms) shows an example in which the angle at which the tone signal of each frequency advances in each sampling cycle is represented by 2 bytes. In addition to the read step table, it is necessary to store a waveform data table for each minute angle in a memory as shown in FIG. If the waveform data table has sine wave data for 1/4 cycle, it can correspond to the waveform data table for one cycle of sine wave and cosine wave. FIG. 7 shows in more detail the part around the basic waveform data output unit 103 of the tone signal detection circuit shown in FIG. In FIG. 7, when the type of the tone signal to be detected is designated by the decode frequency designating circuit 110,
The reading step is obtained from the angle data memory 109 storing the reading step table shown in FIG. Adder 10
In (8), the reading step is added every sampling period to generate a sequentially increasing read address. With this read address, the waveform data memory 107 storing the waveform data table shown in FIG. 6 is accessed to obtain the basic waveform data corresponding to the tone signal to be detected. The memory 104 in FIG. 3 is set in two areas of the waveform data memory 107 and the angle data memory 109 in FIG. The basic waveform data thus obtained and A /
The correlation operation with the D-converted digital signal is performed in the correlator 102. However, in order to detect a plurality of tone signals using the above-described circuit, it is necessary to calculate an angle to be advanced for each sampling cycle of each tone signal, and to calculate the angle in accordance with each tone signal. It is necessary to prepare a memory that stores the readout step table and a memory that stores the waveform data table for each minute angle. Each time the number of tone signals that can be detected increases, a large memory capacity or high performance There is a problem that a processor having a computing ability is required, and the cost of the apparatus is increased. For example, when the frequency of the tone signal specified by the decode frequency specifying circuit 110 is 67.0 Hz,
From the angle data memory 109 in which the read step table of FIG. 5 is stored, a read step of 24.120 degrees (“1127” in HEX display) corresponding to 67.0 is obtained. Next, adder
In 108, a read address that is added in increments of 24.120 degrees (“1127” in HEX display) in synchronization with the sampling frequency and that increases sequentially must be generated. The reading step and the sequentially increasing reading address are different for each tone signal to be detected, so they must be obtained by arithmetic processing each time. Of course, the 2-byte operation and reading are completed within the time of the sampling interval. Therefore, there is a problem that a processor having a low function has a heavy burden, a processor having a high function, that is, a processor having a high cost must be adopted, and the cost of the apparatus increases. In addition, since the readout steps are different for each tone signal, a memory for storing a waveform data table for each minute angle is required in accordance with the readout steps, and a memory for storing a readout step for each tone signal is also required. There is a problem that the circuit configuration becomes complicated and the cost increases. The present invention does not require a processor having a particularly high-performance computing capability and a large amount of memory,
It is an object of the present invention to provide a tone signal detecting circuit capable of detecting a plurality of tone signals. According to the present invention, in order to solve the above-mentioned problems, an input signal is sampled and processed to determine whether any of a plurality of different tone signals is included. A tone signal detecting circuit configured to determine whether a tone signal to be detected is specified, and a frequency output unit that outputs a sampling frequency corresponding to the type of the specified tone signal. Sampling means for sampling an input signal at the sampling frequency and outputting the same as input waveform data; basic waveform data output means for outputting basic waveform data at the sampling frequency; and a correlation between the input waveform data and the basic waveform data. A correlation means for performing a calculation and outputting a correlation value; and the input signal when the correlation value exceeds a predetermined threshold value. And means for determining that the tone signal includes the designated tone signal. Embodiments of a tone signal detection circuit according to the present invention will be described more specifically with reference to the drawings. FIG. 1 is a block diagram of the tone signal detection circuit of this embodiment. In FIG. 1, reference numeral 1 designates designating means for designating the type of the tone signal Sn to be detected. For example, when any of the three types of tone signals S1, S2, S3 is designated, the designation signal K1 corresponding thereto is designated. , K2, K3. Reference numeral 2 denotes frequency output means for outputting a sampling frequency Ln corresponding to the type of the designated tone signal Sn, and comprises a periodic data output circuit 21 and a sampling frequency generation circuit 22. For example, the tone signal S
When the designated signal K1 is output to detect the signal 1, the periodic data output circuit 21 outputs the periodic data M1 corresponding to the designated signal K1, and the sampling frequency generating circuit 2
2 is a sampling frequency L1 corresponding to the periodic data M1
Is output. 3 is an A / D conversion circuit (sampling circuit)
The analog input signal A is sampled based on the sampling frequency Ln supplied from the frequency output means 2, converted into a digital signal, and output as input waveform data B. Reference numeral 4 denotes basic waveform data output means for outputting basic waveform data C in synchronization with the sampling frequency Ln. Reference numeral 5 denotes a correlation means for performing a correlation operation between the input waveform data B and the basic waveform data C and outputting a correlation value D between them. Numeral 6 denotes a discriminating means for discriminating that the input signal A contains a predetermined tone signal when the correlation value D exceeds a predetermined threshold value E and outputting a detection signal F. For example, if the detection signal F is output while the tone signal S1 is designated by the designation unit 1, it can be determined that the input signal A includes the tone signal S1. In the above configuration, the tone signal Sn, the frequency Jn of the tone signal Sn, the designation signal Kn, and the period data M
n and the sampling frequency Ln are set as shown in Table 1 below. [Table 1] However, J2 = 4/3 × J1, J3 = 2 × J1 M2 = 3/4 × M1, M3 = 1/2 × M1 L2 = 4/3 × L1, L3 = 2 × L1 Thus, If the frequency of the tone signal to be detected is P times, the sampling frequency is also P times. That is, instead of keeping the step angle constant for each sampling regardless of the type of the tone signal, the sampling frequency is changed. That is, regardless of which tone signal is detected, by setting the sampling frequency so that the relationship of sampling frequency = frequency of tone signal × Q is satisfied, the step angle for each sampling cycle is kept constant at 360 degrees / Q. You can do it. For example, when Q = 8, the step angle for each sampling cycle is 360 degrees / 8 = 45 degrees, so a waveform data table as shown in Table 2 below is stored in advance. [Table 2] When it is desired to detect the tone signal S1 as shown in FIG. 2 (1), the tone signal S1 is designated by the designation means 1 and the period data M1 is determined based on Table 1, and the sampling frequency is determined. Determine L1. Under this condition, the table of Table 2 is accessed at a time interval of 1 / L1, and the waveform data is read. As a result, basic waveform data C having a frequency of J1 is generated as shown in (1) of FIG. As described above, while obtaining the basic waveform data C, as shown in FIG. 1, the frequency for accessing the table of Table 2 and the sampling frequency Ln for A / D converting the input signal are as follows. Both are generated from the sampling frequency generation circuit 22 based on the periodic data Mn,
In the A / D converter 3, the input signal A is sampled at the same timing as the access of the table in Table 2, and the input waveform data B is output. The correlation means 5 performs a correlation operation between the basic waveform data C obtained as described above and the input waveform data B, and outputs a correlation value D between them. At this time, since the basic waveform data C and the input waveform data B are input to the correlation means 5 at the same timing, a high correlation value is output if both waveform data include the same frequency component. When the correlation value D exceeds a predetermined threshold value E, the input signal A
And the detection signal F
If the input signal A does not exceed the threshold value E, it is determined that the input signal A does not include a predetermined tone signal, and the detection signal F is not output. Therefore, when the detection signal F is output in a state where the tone signal S1 is designated by the designation means 1, it can be determined that the input signal A includes the tone signal S1. Next, the tone signal S as shown in FIG.
2 is to be detected, the cycle data M2 is calculated as M1 × 3 /
4, and the sampling frequency L2 is 4/3 × L1. Under this condition, the table of Table 2 is changed to 3 / (4 × L
When the access is performed at the time interval of 1), the basic waveform data C of the sine wave having the frequency of 4/3 × J1 is generated as shown in (2) of FIG. In the A / D converter 3, sampling is performed in the same manner as described above with the sampling frequency L2 = 4/3 × L1, and the input waveform data B is output to the correlator 5; It is determined whether or not the same frequency component as the basic waveform data C is included. Furthermore, when it is desired to detect the tone signal S3 as shown in (3) of FIG. 2, the period data M3 is set to M1 / 2 and the sampling frequency L3 is set to 2 × L1, so that the table of Table 2 becomes 1 / ( When access is performed at a time interval of (2 × L1), basic waveform data C of a sine wave having a frequency of 2 × J1 is generated as shown in (3) of FIG. In the A / D converter 3, the sampling frequency L3 = 2 × L1, the sampling is performed in the same manner as described above, the input waveform data B is output to the correlator 5, and the discriminating means 6 outputs the basic waveform to the input signal A. It is determined whether or not the same frequency component as the data C is included. In this way, the frequency of the tone signal to be detected is 4/3 times, 2
In the case of double, the sampling frequency is set to 4/3
By changing the frequency of the basic waveform data to 2/3, the frequency of the basic waveform data can be changed to follow 4/3 times and 2 times. According to the above processing, instead of changing the reading step of the waveform data table, the input signal is sampled at the sampling frequency synchronized with the reading frequency without changing the reading step but changing the reading time interval. By changing the read frequency for accessing the waveform data table for each tone signal to be detected, it is possible to generate basic waveform data of a required frequency without requiring a table of a read step for each tone signal to be detected. Further, unlike the conventional case, a waveform data table for each angle corresponding to one reading step may be prepared without requiring a waveform data table for each minute angle, so that the waveform data table is stored. The amount of memory required for this can be significantly reduced. Note that the waveform data table in Table 2 is an example, and a table corresponding to the reading step is appropriately used. As described above, according to the tone signal detection circuit of the present invention, instead of changing the reading step of the waveform data table, the sampling frequency of the input signal is changed without changing the reading step. Since the waveform data table is read out in synchronization with the sampling frequency, it is possible to generate basic waveform data of a required frequency for each tone signal to be detected without requiring a table of a read step for each tone signal. Therefore, not only is a memory for storing a table of readout steps unnecessary, but also a memory capacity for storing a waveform data table can be reduced, and an addition operation based on different readout steps becomes unnecessary. As a result, various types of tone signals can be detected without increasing the cost. The effect is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing a configuration of an embodiment of a tone signal detection circuit according to the present invention. FIG. 2 is a waveform chart showing types of tone signals in the embodiment. FIG. 3 is a configuration diagram of a conventional tone signal detection circuit. FIG. 4 is a waveform diagram showing types of tone signals in a conventional example. FIG. 5 is a diagram showing a step of reading a waveform data table in a conventional example. FIG. 6 is a diagram showing a waveform data table in a conventional example. FIG. 7 is a detailed configuration diagram of a main part of a conventional example. [Description of Signs] 1 Designating means 2 Frequency output means 21 Periodic data output circuit 22 Sampling frequency generation circuit 3 A / D conversion circuit (sampling circuit) 4 Basic waveform data output means 5 Correlation means 6 Determination means S1, S2, S3 Sn tone signal J1, J2, J3, Jn Tone signal frequency K1, K2, K3, Kn Designated signal L1, L2, L3, Ln Sampling frequency M1, M2, M3, Mn Periodic data A Analog input signal B Input waveform data C Basic waveform data D Correlation value E Threshold value F Detection signal

Claims (1)

(1) A tone signal configured to determine whether any of a plurality of different tone signals is included by sampling and processing an input signal. A detection circuit, designating means for designating a type of tone signal to be detected, frequency output means for outputting a sampling frequency corresponding to the designated type of tone signal, and sampling an input signal at the sampling frequency. Sampling means for outputting as input waveform data, basic waveform data output means for outputting basic waveform data at the sampling frequency, correlation means for performing a correlation operation between the input waveform data and the basic waveform data and outputting a correlation value; When the correlation value exceeds a predetermined threshold value, it is determined that the input signal includes the designated tone signal. Tone signal detecting circuit, characterized in that a discriminating means for outputting a detection signal.