JPH1051328A - Squelch control circuit for receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate a control circuit under an optimum setting at all times without the need for setting by variable resistors for all operating frequencies by solving a problem of setting by the variable resistors for each frequency depending on the frequency characteristic in a conventional squelch control circuit. SOLUTION: An analog switch 1 inserted to an audio signal line is subject to close/open control by a CPU 5. The CPU 5 compares a reception level with a set value and provides an output of a squelch control signal to control the switch 1. A value set by a variable resistor 2 is stored by the CPU 5 into a memory 6 together with frequency data of a received signal and the stored setting data are read corresponding to the frequency based on the received frequency data and the read signal is compared with a level of a received signal and a squelch control signal is outputted. Thus, a noise signal is eliminated from the audio signal line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a squelch control circuit for a receiver.

[0002]

2. Description of the Related Art In a receiver, a squelch control circuit is used to prevent noise from being output from a speaker or the like when there is no reception signal input from an antenna.

FIG. 2 is a block diagram of a conventional squelch control circuit. A received signal received by an antenna is demodulated and input to the squelch control circuit as an audio signal. The audio signal is output to a speaker or the like through an analog switch 1 for closing / opening a signal line.

The closing / opening control of the analog switch 1 is performed by using a comparator 7. The comparator 7 receives a reception level value obtained by detecting a part of the reception signal and a set value obtained by setting the power supply voltage by the variable resistor 8.
The comparator 7 compares these two values, and when the reception level value exceeds the set value, the analog switch 1 is closed and the audio output is output to a speaker or the like.・ Control to open switch 1.

[0005]

In the above-mentioned conventional squelch control circuit, normally, when there is no reception signal, the analog switch 1 is opened so that noise is not output to an audio signal line (output to a speaker or the like). Variable resistor 8
Is set to the highest sensitivity point. However, since the reception level value changes depending on the frequency due to the frequency characteristics of the receiver, the analog switch 1 is closed and the noise is output depending on the frequency. Therefore, there is a disadvantage that the value of the variable resistor 8 must be changed every time.

An object of the present invention is to solve the problem of setting the variable resistor for each frequency based on the frequency characteristic, and to always squelch the optimum setting without changing the setting of the variable resistor at all operating frequencies. It is to provide a squelch control circuit capable of controlling.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to provide a CPU that compares a reception level of an audio signal with a set value and outputs a squelch control signal. And a memory for storing and reading a set value to be compared with the reception level.

According to the above means, the CPU compares the reception level of the audio signal with the set value of the variable resistor or the like, outputs a squelch control signal, and closes / opens the audio signal of the receiver with an analog switch. Squelch control. Further, the CPU stores the set value to be compared with the reception level in the memory for each frequency based on the frequency data of the reception signal. Further, the CPU operates so as to output the squelch control signal by reading the set value stored in the memory from the next time based on the frequency data of the received signal and comparing it with the received level.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a squelch control circuit according to an embodiment of the present invention. A signal received by the receiver is demodulated by a demodulation circuit (not shown) and input as an audio signal. An analog switch 1 for closing / opening the squelch control is inserted into the audio signal line, and the audio signal is output to a speaker or the like through the switch 1. The closing / opening control of the analog switch 1 is performed using the CPU 5.

The CPU 5 compares the reception level value digitized by the analog / digital converter 3 with the set value input from the variable resistor 2 and digitized by the analog / digital converter 4, and When the received signal level is equal to or greater than the set value, the squelch control signal for controlling the analog switch 1 to be closed and for controlling the analog switch 1 to be opened when the received level value is equal to or less than the set value are output.

The variable resistor 2 has an analog resistor to prevent noise from being output to the audio signal line when there is no received signal.
The set value is set to the highest sensitivity point so that the switch 1 is opened. Since the reception level changes depending on the frequency due to the frequency characteristics of the receiver, the set value is reset to the optimum value each time depending on the frequency.

The CPU 5 stores the set value of the variable resistor 2 in the memory 6 for each frequency based on the frequency data of the received signal. As for the stored data, in the next operation of the receiver, the stored set value corresponding to the frequency is read out based on the frequency data of the received signal and compared with the received level value.

Since the set value to be compared with the reception level is stored in the memory 6, it is not necessary to set the set value to the optimum value by the variable resistor 2 in the operation of the receiver. The squelch control signal can be output by reading the set value data from No. 6 and comparing it with the reception level. Even if the frequency of the received signal changes, the data stored in the memory 6 stores the set value for each frequency based on the frequency data, so the CPU 5 reads the set value data corresponding to the frequency of the received signal. be able to. Thus, even if the frequency changes, the reception level can always be compared with the optimum set value, and the closing / opening control of the analog switch 1 is appropriately performed by the comparison signal, so that the noise output of the audio signal line is always suppressed. it can.

[0015]

As described above, according to the present invention, there is no need to set a set value for each frequency of the squelch circuit based on the frequency characteristics, and the operator can operate the receiver without bothering the setting work. There is.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional squelch circuit.

[Explanation of symbols]

1 ... Analog switch, 2 ... Variable resistor, 3,4 ... Analog to digital converter, 5 ... CPU, 6 ... Memory.

Claims (1)

[Claims] 1. A squelch control circuit for squelch controlling an audio signal of a receiver according to a reception level, a CPU for comparing a reception level of the audio signal with a set value and outputting a squelch control signal, and A squelch control circuit for a receiver, comprising: a memory for storing a set value to be compared with the reception level for each frequency based on frequency data of a signal and reading the set value.