JPH0630448B2 - Interference detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention solves a problem of the interference detection apparatus proposed by the applicant on the same date that an error occurs in interference detection due to an increase in noise in a weak electric field. Therefore, by making the bias voltage of the rectifier circuit variable according to the electric field strength, interference detection can be performed with high accuracy regardless of the electric field strength.

[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, accurately detecting the interference (DU ratio) of the D wave and the U wave leads to an improvement in the quality of the system, and therefore an apparatus 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 and IF output, mean square ^{_{2 <E D 2><E}} L 2> low-frequency component of the future high-frequency component mean values _{^{<E D 2> + <E}} U 2> and the obtained 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 squared envelope detection, it is necessary to obtain the levels of the D wave and the U wave from the high frequency component and low frequency component of the envelope detection to detect interference. 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. 5, 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 requires highly accurate measurement of the D wave level. As compared with the conventional example, the circuit can be configured more easily, 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. Then, this is detected as the amount of interference.

That is, the device shown in FIG. 5 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.
With a configuration in which the DC bias voltage is varied according to the DC component of the logarithmic detection circuit 1, only the high frequency component is extracted from the logarithmic detection signal from this circuit 1 and the D
It comprises a rectifier circuit 9 for obtaining a C value.

[Action]

When the noise component is superimposed on the weak electric field, the DC bias voltage of the full-wave rectifier circuit 7 is lowered by the output of the DC amplifier 8.
As a result, it is possible to prevent the integral value from increasing due to the noise component. Therefore, without being affected by noise components,
Only the magnitude of the high frequency component due to interference can be extracted.

〔Example〕

FIG. 1 shows a block diagram of the present invention. In FIG. 1, the same components as those in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted. In the figure, 7 is a full-wave rectifier circuit, whose bias voltage is variable according to the signal level obtained by amplifying the output of the logarithmic detection circuit 1 by a DC amplifier 8, and has the configuration shown in FIG. . That is, as shown in FIG. 2C, the bias voltage of the full-wave rectifier circuit 7 is maintained at a predetermined level when the electric field strength is a relatively high electric field level (A or more) of about 10 dBμ or more and 10 dBμ. In the following comparatively low electric field level (A or less), the electric field strength is varied below a predetermined level. The high-pass filter 3, the AC amplifier 4, the full-wave rectifying circuit 7, and the integrating circuit 6 constitute a rectifying circuit 9.

First, if the noise component is not superimposed by 10dB about more strong electric field, the high frequency component output a of for example 100 mV _P-P of the high-pass filter 3 (FIG. 4 (A)) is amplified by an AC amplifier 4 Te example 300 mV _P-P of the signal b is a (FIG. 4 (B)), is supplied to the full-wave rectifier circuit 7. Here, full _- wave rectification is performed to form a full _- wave rectification waveform of 150 mV PP, and a signal c (FIG. 4C) is obtained by using, for example, a voltage of 2.5 V from the DC amplifier 8 as a bias voltage. The full-wave rectified signal c is integrated by the integrator circuit 6 (bias voltage 2.5
V) + 150mV = 2.65V DC voltage d (Fig. 4 (D))
And this is taken out as the amount of interference.

Next, a case where a noise component is superimposed on a weak electric field of about 10 dBμ or less will be described. When the output of the AC amplifier 4 by the noise component is superimposed and become for example 600 mV _P-P, the full-wave rectified waveform by full wave rectification circuit 7 30
It becomes 0m _VP-P . In this case, the bias voltage of the full-wave rectification circuit 7 due to the voltage from the DC amplifier 8 is lower than 2.5 V shown in FIG. 4C (for example, 1/2 of the amplitude of the output of the AC amplifier 4 which is increased by the noise component). , That is,
150mV _P-P decrease) to. From this, the bias voltage is
2.35V, integrated by the integration circuit 6, 2.65V DC
It becomes a voltage.

In this way, when the noise component is superimposed on the weak electric field, the bias voltage of the full-wave rectifier circuit 7 is reduced by the amplitude of the noise component, so that the high frequency due to interference is not affected by the noise component. Only the size of the ingredients can be retrieved.

On the other hand, when there is no interference and there is only a noise component in an extremely weak electric field, the bias voltage of the full-wave rectifier circuit 7 is set to be extremely low as shown in FIG. Is taken out extremely low and is not detected as the amount of interference.

〔The invention's effect〕

According to the present invention, in particular, when a noise component is generated in a weak electric field, the amount of interference can be accurately detected without being affected by the noise component, and the dynamic range of interference detection can be widened.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of the present invention, FIG. 2 is a schematic operation explanatory view of FIG. 1, FIG. 3 is a circuit diagram of a main part of FIG. 1, and FIG. FIG. 5 is a block diagram of an apparatus proposed by the applicant on the same date as the operation explanatory view of the circuit shown in the figure. In the figure, 1 is a logarithmic detection circuit, 3 is a high-pass filter, 6 is an integration circuit, 7 is a full-wave rectification circuit, 8 is a DC amplifier, and 9 is a rectification circuit.

Claims (2)

[Claims] 1. A circuit (1) for logarithmically detecting a signal of a received radio wave including an interfering wave in an interference detecting device for detecting interference due to an interfering wave of the same frequency in a multi-channel mobile communication system which repeatedly uses the same frequency. )
A circuit in which the DC bias voltage is varied according to the DC component of the circuit (1), and only the high frequency component is extracted from the logarithmic detection signal from the circuit (1) to obtain a DC value corresponding to its amplitude (9) An interference detection device comprising: 2. The interference detection device according to claim 1, wherein the DC bias voltage is set to be low when a weak electric field of a desired wave is set.