JPS5911037A - Receiver - Google Patents

Abstract

PURPOSE:To make the operation of a squelch circuit stable, by providing an electronic switch between the clock input section of a sound frequency circuit including a switched capacitor filter and the output section of a clock generating circuit for intermitting a clock with a squelch control signal. CONSTITUTION:A sound signal at an intermediate frequency signal terminal 12 is demodulated at a demodulator 11, applied to a sound frequency circuit 1 including the switched capacitor filter and a sound signal 4 is outputted at a sound output terminal 5. The electronic switch 2 is provided between the clock input section 7 of the circuit 1 and the clock output section of the clock generating circuit 3 and a squelch control signal from a squelch signal input terminal 6 is applied to the switch 2. The clock from the generating circuit 3 is intermitted at the switch 2 with the squelch control signal from the terminal 6 so as to make the operation of the squelch circuit stable, allowing to miniaturize the squelch circuit and to attain the lower power consumption.

Description

[Detailed Description of the Invention] Generally, a receiver has a squelch circuit that squelches noise generated inside the receiver when there is no signal input, and a filter circuit that eliminates noise contained in the signal. Equipped with However, in conventional receivers, the squelch circuit and the filter circuit are configured separately, so there is a drawback that the mounting space becomes large. or,
In conventional squelch circuits, the power supplied to the squelch circuit is turned on and off using a transistor, which has the disadvantage of making the circuit operation unstable.

SUMMARY OF THE INVENTION An object of the present invention is to provide a receiver that solves the above-mentioned conventional drawbacks.

The receiver according to the present invention includes at least a clock generation circuit for driving a switchback capacitor filter for the high frequency band, a clock generation circuit for driving the switchover capacitor filter, and an electronic circuit for intermittent clock output from the clock generation circuit. Equipped with Suinochi table. And the electronic switch is
It is provided between the clock input section of the switching filter and the clock output section of the clock generation circuit, and is controlled by a control signal for squelching the noise generated inside the receiver. Therefore, in the present invention, the suinotide capunk filter constitutes the signal squelch switch.

A detailed explanation will be given below with reference to the drawings.

FIG. 1 is a circuit diagram showing the configuration of a squelch circuit used in a conventional receiver. In the figure, 20 is a power supply terminal to the circuit, 21 is a transistor for turning on and off the power supply from the power supply to the differential amplifier 29, and 22 is a capacitor 23 to 28 is a resistor.

2≦) is a differential amplifier for amplifying the signal or for cutting off the signal circuit when the stain source supply is turned off by the transistor 2J, and 30 is a squelch signal input terminal.

311d: audio input terminal; 32 represents an audio output terminal.

In FIG. 1, when a squelch signal is used to cut off the signal circuit and bring it into a switching state, an input voltage having approximately the same potential as the power supply is supplied to the squelch signal input terminal 30. As a result, the transistor 21 is turned off and the power supply to the differential amplifier 29 is cut off, so that the differential amplifier 29 becomes inoperable and the connection between the audio input terminal 31 and the audio output terminal 32 is electrically disconnected. In this case, it is easy to ensure a signal cutoff amount, that is, a signal attenuation amount of 50 dB or more.

The circuit has the following drawbacks. That is.

The DC potential of terminals 31 and 32 changes as the transistor 21 turns on and off because the transistor 2I turns the power on and off. Such potential fluctuations at the terminals 31 and 32 often work in a direction that interferes with the normal operation of the circuit.

For example, this transient potential fluctuation may reduce the noise level of the amplifier at the subsequent stage, or if a redundant speaker is connected, it may cause a clicking sound when the squelch circuit operates. A commonly used means to alleviate this disadvantage is to add a capacitor 22 to the differential amplifier's power supply. This is a means devised so that the power supply does not change on and off in steps, but changes gradually with an appropriate time constant. Although this means is effective, it has the disadvantage that the response speed of the squelch circuit is limited because it has a time constant of 1.

FIG. 2 is a block diagram showing a partial configuration of a receiver using the present invention. The intermediate frequency signal from the intermediate frequency signal terminal 12 becomes an audio signal demodulated by the demodulator 11. This audio signal is input from the audio signal input terminal 4 to an audio frequency circuit l including a suinotide capacitor filter (hereinafter abbreviated as SCF).
is input.

- On the other hand, the clock for driving the SCF is generated by the clock generation circuit 3 and is supplied from the clock input section 7 of the audio frequency circuit 1 via the electronic switch 2 having the squelch signal input terminal 6.

The electronic switch 2 is turned on and off by a control signal input also to the squelch signal input terminal 6.

FIG. 3 is a waveform diagram for explaining the operation of FIG. 2,
(a) is an input signal input from the audio input terminal 4, (b)
(C) shows an example of the squelch signal input terminal 60 control signal, and (C) the output signal output from the audio output terminal 5. The input signal (a) is a voice band signal with out-of-band noise superimposed. At time 1o-1, switch 2 is turned on by the control signal (b).

In this state, the clock generated from the clock generation circuit 3 is input as is to the clock input section 7 of the audio frequency circuit 1, and the input signal (a) is input to the SC of the audio frequency circuit 1.
Out-of-band noise is removed by F, resulting in an output signal (C). on the other hand.

During time t1 to t2, electronic switch 2 receives control signal (
b) is in the off state. In this state, the clock from the clock generation circuit 3 is cut off by the electronic switch 2, and no clock is supplied to the clock input section 7 of the audio frequency circuit 1. Therefore, S of audio frequency circuit 1
The CF does not operate, and the input signal (a) is not available at the output of the audio frequency circuit 1. Furthermore, after time t2, the above-mentioned time t. - Operates the same as tl.

It can thus be seen that the device shown in FIG. 2 not only operates as a filter but also has a squelch circuit that can cut off the audio signal in response to a control signal.

The above-mentioned SCF is composed of an electronic switch, an operational amplifier, and a capacitor, and can be easily integrated into an IC using MOS+-Lannostar circuit technology.

To operate the SCF, a clock is required to drive its electronic switches, and the frequency stability of the clock generation circuit that supplies this clock is also good. Still SCF QI
Although the absolute value of capacitance varies considerably when converting to C, the capacitance ratio can be realized with high precision on the same wafer. Moreover, since two SCF KMOS transistors are used, power consumption can be reduced. Using an SCF in the audio band filter of the receiver in this way is useful for downsizing, increasing reliability, and saving power consumption.

Map ξ2 The electronic switch used to connect and disconnect the clock signal in the present invention is the most basic 2 as a logic gate.
It can be easily configured with a single staff member.

This circuit is also suitable for IC implementation.

As is clear from the above description, there are two aspects of the present invention.

Unlike conventional squelch circuits, the operation does not become unstable, and the filter circuit and squelch circuit of the receiver can be made smaller and more economical.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing the configuration of a squelch circuit used in a conventional receiver, Figure 2 is a block diagram showing a partial configuration of a receiver using the present invention, and Figure 3 is a circuit diagram showing the configuration of a squelch circuit used in a conventional receiver. FIG. 3 is a waveform diagram for explaining the operation shown in the figure. Explanation of symbols 1...Audio frequency circuit including a suinotide capacitor filter, 2...Electronic switch, 3...Clock generation circuit, 4...Audio input terminal, 5.Audio output terminal. 6... Squelch signal input terminal, 7... Clock input section. 11... Demodulator, 12 Intermediate frequency signal end f, 20...
・Power supply terminal, 21...Transnostar for power on/off, 22.Capacitor, 23-28...Resistor, 29...
Differential amplifier, 30... Squelch signal input terminal. 31... Audio input terminal, 32 Audio output terminal.

Claims (1)

[Claims] 1 At least a voice band switched capacitor filter, a clock generation circuit that supplies a clock for driving the switch capacitor filter, a clock input section of the switch capacitor filter, and a clock output section of the clock generation circuit. 1. A receiver comprising: an electronic switch provided between the clock generating circuit and the electronic switch that connects and cuts the clock from the clock generating circuit in response to a squelch control signal.