JPH02280431A - Sensitivity deterioration detection system for fm communication line - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for detecting a decrease in sensitivity in an FM communication line during communication.

[Conventional technology]

When a decrease in sensitivity occurs due to interference or line failure during communication on an FM communication line, it is necessary to detect this as soon as possible, evacuate from the defective line, and prevent radio wave jamming. Examples of methods for detecting interference during communication are as follows. ■ Upper out-of-band tone signal system (AMPS system)
e) Out of the three types, one wave assigned to each zone is superimposed and transmitted. The original purpose of this method is to prevent erroneous connections due to overreach to other zones. Regarding interference, radio waves being communicated in the own zone are masked, and strong interfering radio waves that suppress tone signals can be detected. ■Beat detection method: This method determines the degree of interference based on the beat phenomenon caused by interference. It is currently under development and has not yet been put into practical use (IEICE Communication Method Study Group Material C383-13, etc.). As a simple method, a method has been considered in which reception is subjected to AM detection and interference is detected from the magnitude of the AM component. ■ Beat frequency detection method outside the lower band (below 300 Hz): When interference occurs, a frequency that is the frequency difference between the two waves is generated as a demodulated output, so this is a method for detecting this.

[Problem to be solved by the invention]

Each of the above-mentioned methods (1) to (2) has drawbacks such as poor practicality and poor detection accuracy. The present invention eliminates these drawbacks, has excellent detection accuracy, and
The present invention provides a method for detecting a decrease in the sensitivity of an FM communication line, which is highly practical in order to avoid interfering lines and prevent radio wave jamming.

[Means to solve the problem]

In order to solve the above problems, the sensitivity reduction detection method of an FM communication line to which the present invention is applied uses a frequency divided from the communication frequency band or a frequency outside the communication frequency band on the transmitting side, and uses a frequency that is divided from the communication frequency band or a frequency outside the communication frequency band, and uses a frequency that is divided from the communication frequency band on the transmitting side. It is characterized by transmitting a fixed data signal in a superimposed manner, reproducing the received data signal on the receiving side, and measuring the error rate of the reproduced signal to detect a decrease in sensitivity. [Embodiment 1] Hereinafter, an embodiment of a method for detecting a decrease in sensitivity of an FM communication line to which the present invention is applied will be described in detail. FIG. 1 is a block diagram of an FM communication device for implementing the FM communication line sensitivity reduction detection method of the present invention. In the figure, 2 is a filter, 3 is an overmodulation prevention circuit, 4 is an encoding circuit, 5 is a modem, 6 is a modulation circuit, 7 is a transmitter, and 8
is a transmitting antenna, and 5 or more are on the transmitting side l. Also 1
1 is a receiving antenna, 12 is a receiver, 13 is a modem, 14
1 is a signal processing circuit, 15 is a monitor switch, and the above are on the receiving side 10. In the above circuit block, the tone component used for data transmission is first removed from the audio signal by the filter 2, and the amplitude intensity is suppressed by the overmodulation prevention circuit 3. On the other hand, the data signal is encoded by the encoding circuit 4 and modulated by the modem 5. These audio signals and data signals are superimposed, modulated into a transmission signal by the modulation circuit 6, amplified by the transmission ff17, and then transmitted through the transmission antenna 8 as a communication wave f. The communication wave fn is received through the receiving antenna 11, detected and amplified by the receiver 12, and separated into a voice signal and a data signal. The data signal is demodulated and reproduced by the modem 13 and output from the signal processing circuit 14. Further, the signal processing circuit 14 determines the error rate of the reproduced data signal and outputs it as a judgment output. On the other hand, the audio signal is input from the receiver 12 to the monitor switch 15. In the monitor switch 15,
The circuit is opened or closed based on the judgment output input from the signal processing circuit 14. That is, when the error rate of the data signal is small, the monitor switch 15 is turned on and audio is output. When interference waves and disturbance waves fu are received by the receiver 12 through the receiving antenna 11, the error rate of the data signal demodulated and reproduced by the modem 13 becomes high (in that case, the judgment output input from the signal processing circuit 14 The monitor switch 15 is turned off to cut off the audio, and if necessary, the judgment output is obtained and the radio frequency is switched, thereby evacuating from the interfering line. , high-speed data is not required, so it is possible to use both the tone squelch frequency and the modem frequency. Since the error rate of the data signal is used as the detection criterion, it is easy to set the detection level for sensitivity reduction. The detection accuracy of degradation is also high.Error rate?
lII+ constant does not directly measure bit errors (
This can be done by measuring the number of error correction processes, which simplifies the circuit configuration. Of course, if the data is simple, it is possible to transmit the data overlappingly with the voice. [Effects of the Invention] As explained above, the FM communication line sensitivity reduction detection method to which the present invention is applied has excellent detection accuracy, so it is possible to quickly evacuate from interfering lines and prevent radio wave jamming. It is extremely practical. Furthermore, since the circuit configuration for implementing the method of the present invention is simplified, the device becomes small and simple.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an FM communication device for implementing the FM communication line sensitivity reduction detection method of the present invention. l...Transmitting side device 3...Overmodulation prevention circuit 5...Modem 7...Transmitter IO...Receiving side device 12...Receiver 14...Signal processing circuit

Claims (1)

[Claims] 1. On the transmitting side, a frequency divided from the communication frequency band or a frequency outside the communication frequency band is used to transmit a fixed or non-standard data signal superimposed on the voice, and the received data signal is transmitted on the receiving side. A method for detecting a decrease in sensitivity of an FM communication line, characterized in that a decrease in sensitivity is detected by reproducing and measuring the error rate of the reproduced signal.