JPH0258935A - Receiving mode switching circuit - Google Patents

Abstract

PURPOSE:To eliminate the need for a mute circuit by composing a mode switching circuit of a demodulating signal selective control circuit and a logic circuit and outputting a logic signal with the level of a squelch signal. CONSTITUTION:The title circuit is equipped with a logic circuit 5 to logic- operate mode switching signals A-C and a squelch signal D and to output mode switching control signals A'-C' and a demodulating signal selective control circuit 4 to selectively switch or ON/OFF-control demodulating signals from respective demodulators 1-3 by the mode switching control signals A'-C'. When the squelch signal is outputted, the mode switching signals are outputted, the demodulating signal in a corresponding mode is made to selectively pass, and when the squelch signal is not outputted, the mode switching signals are not outputted, and even when the selecting signal in the corresponding mode is outputted, the demodulating signal is interrupted. Thus, the mute circuit is made unnecessary, and a circuit a constitution can be simplified.

Description

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

The present invention relates to a receiving mode switching circuit that receives demodulated signals from a plurality of demodulators and selects and switches the corresponding demodulated signals by inputting a mode switching signal for selecting these demodulated signals.

[Traditional techniques]

As shown in FIG. 2, the conventional reception mode switching circuit includes an SSB demodulator 21, an AM demodulator 22, and an FM demodulator 23.
, a mode switching circuit 24, and a mute circuit 27, and the corresponding demodulated signal is selected by the SSB selection newsletter A1AM selection signal B and FM selection signal C, and when the signal to be received is below a predetermined signal strength level. The mute circuit 27 is activated by the squelch signal and is configured to prevent the signal from passing through.

[Issue to be solved]

However, since the conventional reception mode switching circuit as described above includes the mode switching circuit 24 and the mute circuit 27 independently, the circuit configuration of the mute circuit becomes complicated and the mute circuit is not sensitive to low frequency signals. Since the control is directly controlled, there are disadvantages in that stability is poor and the response is not fast.

[Means to solve the problem]

In order to solve the above problems, the present invention provides reception mode switching in which demodulated signals from a plurality of demodulators are input and a corresponding demodulated signal is selectively switched by inputting a mode switching signal for selecting these demodulated signals. The circuit includes a logic circuit that performs a logical operation on the mode switching signal and the squelch signal and outputs a mode switching control signal, and a demodulation circuit that selectively switches or ON10 FF controls demodulated signals from each demodulator using the mode switching control signal. A measure was taken to include a signal selection control circuit.

[For production]

According to the present invention, in a receiving mode switching circuit in which demodulated signals from a plurality of demodulators are input and a corresponding demodulated signal is selectively switched by inputting a mode switching signal for selecting these demodulated signals, a mode switching signal is provided. and a logic circuit that performs a logical operation on the squelch signal and outputs a mode switching control signal;
Since it is equipped with a demodulation signal selection control circuit that performs F control, when a squelch signal is output, a mode switching signal is output, and the demodulation signal of the corresponding mode is selectively passed, and when a squelch signal is not output, the mode switching signal is output. No switching signal is output, and even if a selection signal for the corresponding mode is output, its demodulated signal is blocked.

【Example】

Below, the reception mode switching circuit according to the present invention will be explained in detail based on the drawings. FIG. 1 is a block diagram of an embodiment of a reception mode switching circuit according to the present invention. In the drawings, 1 is an SSB demodulator, 2 is an AMM modulator, 3 is an FM demodulator,
4 is a demodulation signal selection control circuit, 5 is a switching control circuit, 6
is a comparator, 7 is a mode switching circuit, A is SSB
B is an AMM selection signal, C is an FMM selection signal, and D is a squelch signal. The mode switching circuit 7 includes the demodulated signal selection control circuit 4 and the switching control circuit 5. When the SSBm selection signal A is input and the squelch signal is larger than the threshold, the output of the comparator 6 becomes the logic level (HIGH), so only the SSB switching control signal ° becomes the (HIGH) level, and the SSB
Only the demodulated signal from the demodulator l is sent to the demodulated signal selection control circuit 4.
The selection is passed. Naturally, the signals from the AMM modulator 2 and the FM demodulator 3 do not pass through the demodulation signal selection control circuit 4. Even if the SSB selection signal A is input, if the squelch signal is smaller than the threshold value, the output of the comparator 6 will be at the logic level (LOW) level, so the SSB switching control signal A' will also be at the [LOW] level. S.S.B.
The demodulated signal from the demodulator 1 also does not pass through the demodulated signal selection control circuit 4. When the AM selection signal B and the FM selection signal are output, the respective mode switching control signals B' and C' are output only when the squelch signal is larger than the threshold value, and the corresponding demodulation is performed in the same manner as described above. The signal passes through the demodulation signal selection control circuit 4. The comparator 6 is not limited to the comparator 6, and other means such as a Schmitt trigger may be used as long as it can output a logic signal depending on the level of the squelch signal. Further, the switching control circuit 5 is not limited to an AND element. In this way, according to the present invention, unlike the conventional mute circuit, the circuit configuration is simplified, and the mute circuit is not required.
There are advantages in terms of space and cost. Further, since the squelch signal performs a logical operation on the logic level mode selection signal and mutes it, control is easy and reliable, and the response can be made faster.

【effect】

According to the present invention, unlike conventional mute circuits, the circuit configuration is simplified and the space is saved.
There are also cost benefits. In addition, logical operations are performed on the logic level mode selection signal using the squelch signal, and the resulting mode switching control signal switches the demodulation signal corresponding to each mode or performs ON10 FF control, making control easy and reliable. At the same time, the effect of faster response can also be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a reception mode switching circuit according to the present invention, and FIG. 2 is a block diagram of an embodiment of a conventional reception mode switching circuit. ■...SSB demodulator, 2-AM demodulator, 3...
FM demodulator, 4... Demodulated signal selection control circuit, 5...
Switching control circuit (logic circuit), 6... Comparator, 7... Mode switching circuit, A... S S B selection signal, B... AM selection signal, C... FM selection signal, D. ... Squelch signal, A', B', C'... Mode switching control signal.

Claims (1)

[Claims] (1) In a receiving mode switching circuit where demodulated signals from a plurality of demodulators are input and a corresponding demodulated signal is selectively switched by inputting a mode switching signal for selecting these demodulated signals, a mode switching signal and a squelch signal are input. and a logic circuit that performs a logical operation on and outputs a mode switching control signal, and the mode switching control signal,
Select or switch the demodulated signal from each demodulator
1. A reception mode switching circuit comprising: a demodulation signal selection control circuit that performs /OFF control.