JPS63215121A - Interference detector - Google Patents

Abstract

PURPOSE:To prevent an error in the detection of interference from being generated in a weak electric field, by taking out an interference detected output only when the specified frequency component of a beat due to a busy control signal is detected. CONSTITUTION:The titled device is constituted of a logarithmic detection circuit 1 which performs the logarithmic detection of the signal of a reception wave including a disturbing wave, a rectifier circuit 2 which takes out only a high frequency component from a logarithmic detection signal from the circuit 1 and obtains a DC value corresponding to the full-wave rectified output of the component, a detection circuit 12 which detects the specific frequency component of the beat due to a control signal being generated in the full-wave rectified output of the busy recitifier circuit 2, and a switching circuit 11 which takes out the output of the rectifier circuit 2 only when the specific frequency component of the beat due to the busy control signal is detected at the detection circuit 12. When a noise component is superposed in a weak electric field, since no specific frequency component due to the busy control signal is detected at a band-pass filter 7, the switch 11 is turned OFF. In such a way, it is possible to prevent the error in the detection of the interference due to the noise from being generated in the weak electric field.

Description

[Detailed Description of the Invention] [Summary] The present invention solves the problem of an interference detection device proposed by the applicant on the same date, in which noise increases in a weak electric field and errors occur in interference detection. Therefore, by configuring the system to output interference detection output only when a specific frequency component of the beat caused by the call control signal is detected, it is possible to avoid errors in interference detection, especially in weak electric fields.

[Industrial application field]

The present invention relates to an interference detection device used in a multi-channel mobile communication system that repeatedly uses the same frequency, such as a car telephone system or a cordless telephone system. In such systems, the S/N ratio of D waves (8 desired waves) may deteriorate due to interference from U waves (interfering waves) of the same frequency, resulting in poor speech clarity; To prevent deterioration of clarity, it is necessary to switch the channel with interference to another channel without interference.

In this case, accurately detecting the interference ratio (DU ratio) of D waves and U waves leads to improved system quality, and therefore a device that can realize interference detection with high viscosity is required.

[Conventional technology]

Conventional interference detection devices perform IF specific output square envelope detection to detect the envelope beat component due to the U wave, and then calculate the root mean square value of the high frequency component, 2<Eo2><Eu2>, and the mean value of the low frequency component. <Eo2>+<Eo2> and interference ratio r=
(<Eu2>/<Eo'>) is obtained. Here, Eo is the amplitude of the D wave, and Eu is the amplitude of the U wave.

This method uses square envelope detection to find the envelope beat component, so in order to detect the interference ratio, it is necessary to find the levels of D and U waves from the high and low frequency components of envelope detection. High accuracy is required for both the measurement accuracy of the D-wave signal and the measurement accuracy of high frequency components due to interference.
There were problems in that the circuit became complicated and measurement variations increased.

Therefore, in order to solve the above problems, the present applicant developed the present invention.
An interference detection device was proposed on the same date as the Akira device.

As shown in Fig. 3, this device includes a logarithmic detection circuit 1 that logarithmically detects a received radio wave signal including U waves, and a high-frequency component due to interference from the logarithmically detected signal from the logarithmic detection circuit 1 through a high-pass filter 3. It consists of a rectifier circuit 2 which extracts only the signal and uses a full-wave rectifier circuit 5 and an integrator circuit 6 to obtain a DC value according to its amplitude.

Since this device logarithmically detects the received signal, its high frequency components can be detected without relying on the total received electric field level that combines the D wave and U wave, thereby increasing the measurement accuracy of the D wave and the bell. The circuit can be constructed more easily than in the conventional example, which requires high accuracy, and since a logarithmic detection circuit is used, there are relatively few measurement errors, and interference can be detected with high precision.

[Problem that the invention seeks to solve]

The IF ratio output of the receiver, generally, as shown in FIG. 2(A), the D wave is 10. Relatively high electric field level (about Eμ or higher)
A), the amount of noise detected is relatively small, but at a relatively low electric field level of about 10 μ or less (A or less), the amount of noise detected is relatively large.゛For this reason, as shown in Fig. 2 (B), the output of the logarithmic detection circuit 1 is a noise component superimposed on a high frequency component due to interference in areas where the electric field strength is relatively low, and as a result, the noise component is rectified and integrated. This is detected as interference.

In other words, the device shown in Fig. 3 detects the noise component as interference ω in a weak electric field, so it can accurately detect the original interference f. However, there was a problem in that it was detected as if there was interference even though there was actually no interference. This does not cause malfunctions when the set interference ratio is low, but especially when the set interference ratio is high, noise components cause malfunctions.

Means for Solving Problem C] As shown in FIG. 1, the interference detection device according to the present invention includes a logarithmic detection circuit 1 that logarithmically detects a received radio wave signal including an interference wave.
and a rectifier circuit 2 which extracts only high-frequency components from the logarithmic detection signal from this circuit 1 and obtains Cflfl according to its full-wave rectified output. Detection circuit 1 that detects a specific frequency component of a beat based on a control signal
2, and a switching circuit 11 which takes out the output of the rectifier circuit 2 only when the detection circuit 12 detects a specific frequency component of the beat based on the call control signal.

[Effect]

When a noise component is superimposed in a weak electric field, the switch 11 is turned off because the specific frequency component of the beat caused by the call control signal is not detected by the bandpass filter 7. This can prevent interference detection errors due to noise when the electric field is weak.

〔Example〕

FIG. 1 shows a block diagram of the present invention, in which the same components as in FIG. 3 are given the same numbers and their explanations will be omitted. The beat detection circuit 12 based on the call control signal 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 the beat caused by the call control signal. in general,
In the above-mentioned mobile communication system, in addition to voice signals, information such as electric field level strength and quality of bit error rate is transmitted as control signals at the same time as the voice signals.

For example, if we consider the case where a digital signal of a lower band (for example, 1008 P S ) is superimposed on a frequency-modulated sound signal, the II 1 of the digital signal
If the carrier wave deviation between II and 0'' is ±0.5kllz, a 1kHz beat will occur when the desired wave side is “1” and the interference wave side is “O” (or vice versa).Usually, the desired wave and interference Since the relationship with the wave side is random, such beats occur frequently.Therefore, by detecting a specific frequency component of the beat with the bandpass filter 7, a strong electric field is detected.

8 is an amplifier, and 9 is a product that integrates the output of amplifier 8.
- Valve circuit 10 is a comparison circuit that compares the output of the integrating circuit 9 with a reference level at a predetermined ratio.

First, when there is a strong electric field of about 10 cEμ or more and no noise component is superimposed, the low frequency component of the beat due to the call control signal is detected from the output of the full-wave rectifier circuit 5 by the bandpass filter 7, and is amplified by the amplifier 8. , are integrated by the integrating circuit 9. The output of the integrating circuit 9 is compared with a predetermined reference level in a comparator circuit 10, and when it is higher than the reference level, it is taken out as an output signal and a switch 11 is turned on. switch 1
1, the output of the rectifier circuit 2 is taken out despite interference.

Next, a case will be described in which a noise component is superimposed in a weak electric field of about 10 dBμ or less. In such a weak electric field, the low frequency component of the beat caused by the call control signal is not detected by the bandpass filter 7, and therefore there is no output from the comparison circuit 10. As a result, the switch 11 is turned off, and the output of the rectifier circuit 2 is not taken out. Therefore, if J3 is in a weak electric field, it will not detect noise and determine that there is interference, and interference detection errors will not occur.

[Efficacy of invention]

According to the present invention, especially when noise components are reduced by (t-) in a weak electric field, interference detection errors will not occur due to noise, improving operational reliability, which is one of the most important features.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a diagram showing the relationship between electric field strength and noise component, and FIG. 3 is a block diagram of a device 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, 6.9 is an integration circuit, 7 is a bandpass filter, 11 is a switch, and 12 is a call control signal detection It is a circuit. Agent Patent attorney +1 digit Meat - 1, d..., -X7 This invention (pro I2 possible

Claims (1)

[Claims] In a mobile communication system that transmits a control signal in addition to a voice signal during a call, an interference detection device that detects interference due to interference waves of the same frequency detects received radio waves including interference waves. A logarithmic detection circuit (1) that performs logarithmic detection; a rectifier circuit (2) that extracts only high frequency components from the logarithmic detection signal from the circuit (1) and obtains a DC value corresponding to its full-wave rectified output; a detection circuit (12) that detects a specific frequency component of a beat caused by the control signal occurring in the full-wave rectified output of the rectifier circuit (2); and a detection circuit (12) that detects a beat caused by the call control signal. The above rectifier circuit (2) is activated only when a frequency component is detected.
1. An interference detection device characterized by comprising a switching circuit (11) for taking out the output of the device.