JPH0630450B2 - Interference detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention solves the problem of the interference detection apparatus proposed by the applicant on the same date that the interference detection error occurs due to an increase in noise in a weak electric field. Therefore, the interference detection output is taken out only when the specific frequency component of the beat by the control signal during a call is detected, so that an error does not occur in the interference detection especially in a weak electric field.

[Industrial application field]

The present invention relates to an interference detecting device used in a mobile communication system of a multi-channel system that repeatedly uses the same frequency such as a car telephone system and a cordless telephone system. In such a system, the SN ratio of the D wave (desired wave) may be deteriorated due to the interference of the U wave (interfering wave) of the same frequency, and the intelligibility of the voice may be deteriorated. It is necessary to prevent the deterioration of the degree and switch the interference channel to another interference-free channel.

In this case, accurate detection of the D-wave and U-wave interference ratio (DU ratio) leads to an improvement in the quality of the system, and therefore a device capable of realizing the interference detection with high accuracy is required.

[Conventional technology]

Conventional interference detection device detects the envelope beat components caused by the U wave to square envelope detection the IF output, from which the mean square value of the high-frequency component 2 <E D _2> and ^<E U ^_2> low-frequency The average value of the components <E _D ² > + <E _U ² > is obtained, and the interference ratio “=
(<E _U ² > / <E _D ² >) is obtained. Where _ED is D
The amplitude of the wave, the E _U is the amplitude of the U wave.

Since this method obtains the envelope beat component by the squared envelope detection, it is necessary to obtain the levels of the D wave and the U wave from the high frequency component and the low frequency component of the envelope detection in order to detect the interference ratio. High accuracy is required for both the measurement accuracy of the D wave level and the measurement accuracy of the high frequency component due to interference.
There is a problem that the circuit becomes complicated and the measurement variation becomes large.

Therefore, the present applicant proposed an interference detection device on the same date as the device of the present invention in order to solve the above problems. This one is
As shown in FIG. 3, a logarithmic detection circuit 1 for logarithmically detecting a received radio wave signal including a U wave, and a high-pass filter 3 for extracting only high-frequency components due to interference from the logarithmic detection signal from the logarithmic detection circuit 1. The full-wave rectification circuit 5 and the integration circuit 6 include a rectification circuit 2 that obtains a DC value according to its amplitude.

Since this one performs logarithmic detection of the received signal, its high frequency component can be detected without depending on the total received electric field level of the D wave and U wave, which makes it possible to highly accurately measure the D wave level. The circuit can be configured more easily than the required conventional example, and since the logarithmic detection circuit is used, the measurement error is relatively small and the interference can be detected with high accuracy.

[Problems to be solved by the invention]

As shown in FIG. 2 (A), the IF output of the receiver generally has a relatively small noise detection amount at a relatively high electric field level (A or higher) where the D wave is about 10 dBμ or more, but 10 dBμ.
The amount of noise detection is relatively large at a relatively low electric field level (A or less) of about the same or less. Therefore, as the output of the logarithmic detection circuit 1, as shown in FIG. 2 (B), a noise component is superimposed on a high frequency component due to interference at a place where the electric field strength is relatively low, and as a result, the noise component is rectified and integrated. This is detected as the amount of interference.

That is, the apparatus shown in FIG. 3 detects the noise component as the amount of interference particularly in a weak electric field, so that the original amount of interference cannot be accurately detected, and when there is only a noise component in the weak electric field, Although there is no interference in reality, there is a problem that it is detected as if there is interference. This does not cause a malfunction when the set interference ratio is low, but particularly when the set interference ratio is high, a malfunction occurs due to a noise component.

[Means for solving problems]

As shown in FIG. 1, the interference detection device according to the present invention is a logarithmic detection circuit 1 for logarithmically detecting a signal of a received radio wave including an interference wave.
And a rectifier circuit 2 that extracts only high-frequency components from the logarithmic detection signal from the circuit 1 to obtain a DC value corresponding to the full-wave rectified output, and the above-mentioned control that occurs in the full-wave rectified output of the rectifier circuit 2 during communication. Detection circuit 1 for detecting a specific frequency component of a beat by a signal
2 and a switching circuit 11 for extracting the output of the rectifying circuit 2 only when the detection circuit 12 detects a specific frequency component of the beat by the control signal during a call.

[Action]

When the noise component is superposed by the weak electric field, the band filter 7 does not detect the specific frequency component of the beat due to the control signal during a call, so that the switch 11 is turned off. This makes it possible to prevent interference detection error due to noise in a weak electric field.

〔Example〕

FIG. 1 shows a block diagram of the present invention. In FIG. 1, the same components as those in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted. The beat detection circuit 12 based on the control signal during a call is composed of a bandpass filter 7, an amplifier 8, an integration circuit 9, and a comparison circuit 10. In the figure, a bandpass filter 7 detects a specific frequency component of a beat due to a control signal during a call. Generally, in the above-mentioned mobile communication system, in addition to the voice signal, information such as the strength of the electric field level and the quality of the bit error rate is sent as a control signal simultaneously with the voice signal. For example, when considering a case where a digital signal (for example, 100 BPS) in a band lower than that band is superimposed on a frequency-modulated audio signal, the carrier deviation between the digital signal “1” and “0” is ± 0.5 kHz. For example, if the desired wave side is "1" and the damage wave side is "0" (or vice versa), 1 kHz
The beat of Usually, such a beat frequently occurs because the relationship between the desired wave and the disturbing wave side is random.
Therefore, the band filter 7 detects the specific frequency component of the beat to detect the strong electric field.

8 is an amplifier, 9 is an integrating circuit for integrating the output of the amplifier 8,
Reference numeral 10 is a comparison circuit for comparing the reference level and the output of the integration circuit 9 when the interference ratio is set in advance.

First, when the noise component is not superimposed in a strong electric field of about 10 dBμ or more, the low frequency component of the beat due to the control signal during a call is detected from the output of the full-wave rectifier circuit 5 by the band filter 7, and amplified by the amplifier 8. , Are integrated in the integrating circuit 9. The output of the integrator circuit 9 is compared with a predetermined reference level by the comparison circuit 10, and when it is above the reference level, it is taken out as an output signal and the switch 11 is turned on. Switch 11
When the switch is turned on, the output of the rectifier circuit 2 is taken out as an interference amount.

Next, a case where a noise component is superimposed on a weak electric field of about 10 dBμ or less will be described. In such a weak electric field, the low-frequency component of the beat due to the control signal during a call is not detected by the bandpass filter 7, and therefore the output of the comparison circuit 10 is also absent. As a result, the switch 11 is turned off and the output of the rectifier circuit 2 is not taken out. Therefore, in a weak electric field,
There is no need to detect noise and determine that there is interference,
No interference detection error occurs.

〔The invention's effect〕

According to the present invention, particularly when a noise component is generated in the weak electric field, interference detection error is not caused by noise,
It has features such as improved operational reliability.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a diagram showing the relationship between electric field strength and noise components, and FIG. 3 is a block diagram of an apparatus proposed by the applicant on the same date. In the figure, 1 is a logarithmic detection circuit, 2 is a rectifier circuit, 3 is a high-pass filter, 5 is a full-wave rectifier circuit, 6 is an integrator circuit, 7 is a bandpass filter, 11 is a switch, and 12 is a control signal detection during a call. Circuit.

Claims (1)

[Claims] 1. A mobile communication system that transmits a control signal in addition to a voice signal during a call, and in an interference detection device that detects interference due to an interference wave of the same frequency, the received radio wave signal including the interference wave is logarithmic. A logarithmic detection circuit (1) for detecting, a rectification circuit (2) for extracting only a high frequency component from the logarithmic detection signal from the circuit (1) to obtain a DC value corresponding to the full-wave rectified output, and the rectification during communication A detection circuit (12) for detecting a beat specific frequency component by the control signal generated in the full-wave rectified output of the circuit (2), and a beat specific frequency by the talk control signal in the detection circuit (12). An interference detection device comprising a switching circuit (11) for extracting the output of the rectifier circuit (2) only when a component is detected.