JPS6367778B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diversity type FM receiver, in which a plurality of receiving circuits can be controlled by one squelch circuit without having a control circuit such as a squelch circuit in each of the receiving circuits. By doing this, you can easily obtain good reception conditions.

FIG. 1 shows the configuration of a conventional diversity-type FM receiver.

In FIG. 1, 1a and 1b are front ends, 2a and 2b are intermediate frequency amplifier circuits, 3a and 3b are demodulation circuits, and 4a and 4b are respectively demodulation circuits.
are level adjustment circuits that adjust the output levels of the receiving circuits A and B to the same level, 5a and 5b are squelch sensitivity adjustment circuits, 6 is a diversity control circuit, 7 is a diversity selection switch, 8a and 8
b is a squelch switch that is controlled ON and OFF by squelch signals generated by squelch circuits 11a and 11b. 9 is an output circuit, and 10 is an output terminal.

In the conventional diversity type FM receiver described above, the squelch sensitivity adjustment circuits 5a and 5b and the squelch circuits 11a and 11b weaken the received radio waves due to the level of white noise contained in the demodulated signal from the receiving circuit A or B. If this is detected, turn on squelch switch 8a or 8b.
It is set to OFF so that the demodulated signal of that receiving circuit is not output. On the other hand, the diversity control circuit 6 compares the magnitude of the voltage related to the reception strength output from the intermediate frequency amplification circuits 2a and 2b,
The diversity selection switch 7 is caused to select either receiving circuit A or B having a good receiving condition. In this case, the squelch level of the demodulated signals supplied by the squelch sensitivity adjustment circuits 5a, 5b to the squelch circuits 11a, 11b is adjusted for each squelch sensitivity adjustment circuit, that is, for each receiving circuit. Therefore, in this FM receiver, squelch circuits 11a and 11b are required for each of the receiving circuits A and B, and adjustment of the squelch level by the squelch circuits is complicated. Also,
Since the number of components of the squelch circuits 11a and 11b is considerably larger than that of other circuits, this has disadvantages in terms of miniaturization and cost reduction of the receiver.

The present invention eliminates these drawbacks and will be described below with reference to an embodiment shown in FIG. In the figure, each circuit 1a to 3a, 1b to 3b constituting the receiving circuits A and B, level adjustment circuits 4a and 4b, diversity control circuit 6, squelch sensitivity adjustment circuits 5a and 5b, output circuit 9, and output terminal 10 are shown in FIG. This is the same as the conventional one shown in FIG.

In FIG. 2, 12a is a diversity switch for the output circuit, and 12b is a diversity switch that operates in conjunction with the diversity switch 12a for the output circuit, and supplies a demodulated signal to the squelch circuit 14. 13 is determined by the output of the squelch circuit 14.
This is a squelch gate that is controlled ON and OFF.

In the embodiment configured in this manner, the signals received and demodulated by the receiving circuits A and B are applied to the level adjusting circuits 4a and 4b and adjusted to the same level. At the same time, the demodulated signal is applied to squelch sensitivity adjustment circuits 5a and 5b, and sensitivity adjustment is performed.

The outputs of the intermediate frequency amplification circuits 2a and 2b are applied to the diversity control circuit 6 and compared, and based on the results, the switches 12a and 12b are controlled, and the outputs of the receiving circuits with good reception conditions are squelched. It is applied to the gate 13 and the squelch circuit 14. The signal passing through the squelch gate 13 is outputted via the output circuit 9.

As is clear from the above embodiments, according to the present invention, one squelch circuit can be shared even if the receiving circuit is a diversity type FM receiver with two or more circuits, and the circuit configuration of the receiver is It gets easier. Furthermore, as a result, the number of parts can be reduced, and the receiver can therefore be made smaller. Furthermore, since the squelch sensitivity can be adjusted for each receiving circuit, it is easy to obtain the best condition for the receiver.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional FM receiver, Figure 2 is a block diagram of a conventional FM receiver.
The figure is a block diagram of FM reception in one embodiment of the present invention. A, B...reception circuit, 4a, 4b...level adjustment circuit, 12a, 12b...diversity switch, 13...squelch gate, 14...squelch circuit.

Claims (1)

[Claims] 1. A plurality of receiving circuits that receive and demodulate FM signals, a plurality of level adjustment circuits and a plurality of squelch sensitivity adjustment circuits to which demodulated outputs of the respective reception circuits are applied, and the plurality of level adjustment circuits. a first switch that selects one from among the squelch sensitivity adjustment circuits, and a second switch that operates in conjunction with the first switch to select one of the squelch sensitivity adjustment circuits and apply it to the squelch circuit. , a diversity control circuit that controls the first switch and the second switch so as to select the receiving circuit in the best reception state, and a squelch signal obtained from the squelch circuit passes through the first switch. consists of a squelch gate that gate-controls the signal
FM receiver.