JPH0447493B2 - - Google Patents

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.

[Conventional technology]

As shown in FIG. 2, the conventional reception mode switching circuit includes an SSB demodulator 21, an AM demodulator 22,
It is composed of an FM demodulator 23, a mode switching circuit 24 configured with three series of buffer amplifiers according to the output of the demodulator by transistors, and a mute circuit 27 configured with an analog switch.
The corresponding demodulated signal is selected by the SSB selection signal A, AM selection signal B, and FM selection signal C, and when the signal to be received is below a predetermined signal strength level, the squelch signal activates the mute circuit 27. and was configured to not allow signals to pass through.

[Issue to be solved]

However, since the conventional reception mode switching circuit described above includes the mode switching circuit 24 and the mute circuit 27 independently, the circuit configuration of the mute circuit becomes complicated, and it is difficult to directly respond to low frequency signals. Since it is controlled, it has disadvantages of poor stability and lack of high-speed response.

[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 an AND operation with the mode switching circuit of each mode and the squelch signal to output a mode switching control signal, and a demodulated signal from the demodulator of the corresponding mode according to each mode switching control signal. We took a measure to selectively output only the following.

[Effect]

According to the present invention, in the 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, the mode switching signal is inputted. and a squelch signal, and a logic circuit that performs an AND operation on the signal and the squelch signal to output a mode switching control signal;
The demodulated signal selection control circuit selectively outputs only the demodulated signal from the demodulator of the corresponding mode according to each mode switching control signal, so that when the squelch signal is output, the mode A mode switching control signal corresponding to the switching signal is output from the logic circuit, and the demodulating signal of the mode corresponding to the mode switching control signal is selectively passed through the demodulating signal selection control circuit. And when the squelch signal is not output,
Even if a mode switching signal is input to the logic circuit, no mode switching control signal is output from the logic circuit, and demodulation signals of all modes are blocked in the demodulation signal selection control circuit.

【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 drawing, 1 is an SSB demodulator, 2 is an AM demodulator, 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, and A is an SSB selection signal. , B is the AM selection signal,
C is an FM 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. As shown in FIG. 1, the demodulated signal selection control circuit 4 includes three sets of analog switches 41, 4 using field effect transistors corresponding to each reception mode.
It is equipped with 2,43. Then, the demodulated signal is controlled on/off by a mode switching control circuit input to the control terminal of each analog switch 41, 42, 43, and only the demodulated signal of the mode corresponding to the mode switching signal is selected as the demodulated signal. The signal is configured to be output from the control circuit 4. When the SSB 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] level, so only the SSB switching control signal A' becomes the [HIGH] level, and the analog switch 41 is turned on. Therefore, only the demodulated signal from the SSB demodulator 1 is selectively passed through the demodulated signal selection control circuit 4. Naturally, since the other analog switches 42 and 43 are off, the AM demodulator 2 and FM
The signal from the demodulator 3 does not pass through the demodulated signal selection control circuit 4. Even if the SSB selection signal A is input, if the squelch signal is smaller than the threshold, the output of the comparator 6 will be at the logic level [LOW] level, so the SSB switching control signal A' will also be [LOW].
level, and the analog switch 41 is turned off. Therefore, the demodulated signal from the SSB 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 C 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 analog The switches 42 and 43 are turned on, and the corresponding demodulated signals are sent to the demodulated signal selection control circuit 4.
It passes through. The comparator 6 is not limited to the comparator 6, but any other means such as a squelch trigger or the like 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 manner, the present invention does not require a mute circuit as in the prior art, thereby simplifying the circuit configuration and providing advantages in terms of space and cost. Furthermore, since the squelch signal performs an AND 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 the conventional art, a mute circuit is not required, so the circuit configuration is simplified and advantages are obtained in terms of space and cost. Furthermore, the squelch signal performs an AND operation on the logic level mode selection signal, and the obtained mode switching control signal selectively selects and outputs the demodulated signal corresponding to each mode. Control is easy and reliable, and the response is fast.

[Brief explanation of drawings]

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. 1...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...SSB
Selection signal, B...AM selection signal, C...FM selection signal, D...squelch signal, A', B', C'...mode switching control signal.

Claims (1)

[Claims] 1. 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 logic circuit that performs an AND operation on the mode switching signal and the squelch signal and outputs a mode switching control signal; 1. A reception mode switching circuit comprising: a demodulation signal selection control circuit for selectively outputting a demodulated signal.