JPH0446022B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to receivers, and more particularly to radiotelephone receivers having the ability to detect interference at radio frequencies. In communications, interference is a problem when a limited frequency channel is shared by a large number of users, such as in mobile radio communications. That is, if a channel is already in use and another user uses the same channel, interference will occur in the radio frequency band, making it impossible for both parties to communicate. Although it is possible to reduce the chance of such interference by accurately checking the usage status of a channel before starting communication, this method is not sufficient in mobile radio systems, etc., because the lines are unstable. . If this interference can be detected early while the amount of interference is small, measures such as switching to another channel can be taken, so a receiver that has the function of detecting interference is of practical significance. Conventional methods for detecting interference have been proposed, for example, as described in Kozono and Ishikawa, "Study of co-frequency interference detection method in land mobile communications," Proceedings of the 1985 National Conference of the Institute of Electronics and Communication Engineers, No. 2176 (Reference 1). What is known is what is known. However, this method has the disadvantage that the circuit configuration becomes complicated.

An object of the present invention is to provide a receiver having an interference detection device with a simple circuit configuration.

According to the present invention, there is provided a means for receiving a composite signal of an audio signal and a digital signal; A means for outputting an error signal, a converting means for inputting the error power and outputting a value determined by a predetermined functional relationship, and detecting the output of the converting means as an amount of interference at a radio frequency. can be achieved.

Hereinafter, the present invention will be explained in detail using the drawings. FIG. 1 is a block diagram of a transmitter for performing communications targeted by the receiver of the present invention. Audio signals and digital signals inputted from input terminals 11 and 12, respectively, are combined by a combining circuit 13 and then transmitted by a transmitting circuit 14.
The digital signal may be transmitted specifically for the receiver of the present invention, or may be a data signal transmitted simultaneously with the audio signal. FIG. 2 is a conceptual diagram of a transmission baseband signal spectrum.
The frequencies of the audio signal spectrum 22 and the digital signal spectrum 21 are separated so that they do not overlap. The audio signal is usually
Since it is sufficient to transmit a band of the order of 300Hz to 3KHz, digital signals can be inserted above or below this frequency band. In the embodiment of the present invention, the case is shown in which it is inserted on the lower side. In this way, attempts have already been made to insert a digital signal into the lower band of the voice signal and simultaneously transmit the digital signal.For example, Matsumoto and Hattori, ``Study of busy signal transmission in mobile communications'';
Proceedings of the 1985 National Conference of the Institute of Electronics and Communication Engineers, No.
2201 (Reference 2). The results show that transmission at a transmission rate of about 50 bits/second can be carried out satisfactorily. By transmitting data signals at the same time as audio signals, it is possible to perform various sophisticated controls, such as specifying a channel to which to switch when interference occurs.

FIG. 3 is a block diagram for explaining an example of a receiver using the present invention. The transmitted signal is received by the receiving circuit 31. The output is branched into two, one of which is input to a high-pass filter 32 to obtain an audio signal at an output terminal 33. The other signal is input to a low-pass filter 34 to obtain a digital signal. This signal is determined in the data signal determination circuit 35,
A received data signal is available at a digital signal output terminal 36. The determination error power measurement circuit 37 receives the other output signal of the data signal determination circuit 35 as an input.
The determination error power is output to the data conversion circuit 38.
When interference occurs in the radio frequency band, the received signal waveform deteriorates as shown in FIG. 5, and the determination error voltage ΔD increases as the amount of interference increases. Here, the voltage ±A is a reference voltage. As the determination error voltage increases, the error power also increases. Therefore, as conceptually shown in FIG. 6, the amount of interference has a one-to-one functional relationship with the error power, so the amount of interference can be detected by measuring the error power. . The data conversion circuit 38 is a conversion circuit that inputs the error power and outputs the amount of interference.In practice, the data conversion circuit 38 inputs the error power and outputs the amount of interference.
This can be easily realized using a memory circuit that stores the amount of interference.

FIG. 4 shows the data signal determination circuit 35 and the determination error power measurement circuit 3 indicated by the broken line in FIG.
7 is a block diagram for explaining in detail. The received data signal inputted to the input terminal 41 is sampled by the sampling circuit 42 at the time given by the clock signal generated by the clock regeneration circuit 43, judged by the judgment circuit 44, and the received data signal is sent to the digital signal output terminal 36. I get a signal. A part of the sampled digital signal is input to the subtraction circuit 46, and a difference (ΔD) from the reference voltage output from the reference voltage generation circuit 45, that is, a determination error voltage is obtained. This error voltage is detected by the detection circuit 47.
By subsequently inputting the signal to the low-pass filter 48, the determination error power is measured. here,
The reference voltage generation circuit 45 selects one of two types of reference voltages, A and 1A, depending on the determined received data.

As described above, the present invention can provide a function for detecting the amount of interference by adding a simple circuit to a system that simultaneously transmits audio signals and data signals. If there is a lot of noise, the detection error of the amount of interference will increase, so in this case, it may be practically necessary to add a function to stop the interference detection operation. Furthermore, in a line where fading occurs, the relationship between the determination error power and the amount of interference may change depending on the fading pitch. At this time, a fading pitch detection function is added separately, and depending on the detected value,
It may also be possible to change the relationship between the determination error power and the amount of interference.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a transmitter that transmits signals for reception by the receiver of the present invention, FIG. 2 is a spectrum diagram of data signals and audio signals, and FIG. 3 is an implementation of the receiver of the present invention. FIG. 4 is a block diagram showing details of an embodiment of interference detection in the receiver of the present invention, FIG. 5 is a waveform diagram showing determination error voltage, and FIG. 6 is a diagram showing determination error power and interference. FIG. 2 is a conceptual diagram showing the relationship between quantities. In these figures, 11 is an audio input terminal;
2 is a digital signal input terminal, 13 is a synthesis circuit,
14 is a transmitting circuit, 21 is a digital signal spectrum, 22 is an audio signal spectrum, 31 is a receiving circuit, 32 is a high-pass filter, 33 is an audio signal output terminal, 34 is a low-pass filter, and 35 is a data signal determination circuit, 36 is a digital signal output terminal, 37 is a judgment error power measurement circuit, 38 is a data conversion circuit, 39 is an interference amount detection output terminal, 41 is a received data signal input terminal, 42 is a sample circuit, 4
3 is a clock regeneration circuit, 44 is a determination circuit, 45 is a reference voltage generation circuit, 46 is a subtraction circuit, 47 is a detection circuit, 48 is a low-pass filter, and 49 is a determination error power output terminal.

Claims (1)

[Claims] 1. A means for receiving a composite signal of an audio signal and a digital signal, and outputting a judgment error signal by extracting and judging the digital signal and determining an error between a reference signal based on the judgment result and the extracted signal. a converting means for inputting the error power and outputting a value determined by a predetermined functional relationship; and a means for detecting the output of the converting means as an amount of interference at a radio frequency. Machine.