JPS5910831Y2 - communication device - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to communication devices such as transceivers.

A schematic block diagram of the transceiver is shown in FIG.

The microphone input is inputted via the microphone amplifier 1 to the transmission circuit section 2 including an overmodulation prevention circuit, a modulation circuit, etc.
The signal is input to a microphone input detection circuit section consisting of an amplifier 3 and a detector 4.

The detector 4 converts the output of the amplifier 3 into a positive DC signal, and therefore outputs a positive microphone input detection signal A when there is a microphone input.

On the other hand, the reception input is applied to a reception circuit section 5 including a 1F amplifier, a demodulation circuit, etc., and then is amplified in power by a power amplifier 7 via a squelch gate circuit 6.

This power amplifier output drives a speaker and is applied to a so-called anti-trip circuit section consisting of a buffer amplifier 8 and a detector 9.

This detector 9 converts the output of the buffer amplifier 8 into a negative DC signal, and when a speaker drive signal is present, generates a negative DC level B corresponding to the level of the speaker drive signal.

Both DC signals A and B are applied to the adder circuit 10 and added. However, since A and B have positive and negative levels, respectively, the control signal C corresponding to the difference between the two levels is the addition output. Become.

This control signal C is applied to a transmission state switching signal generation circuit 11 made up of switching elements such as transistors.

By appropriately setting the threshold level of the switching signal generation circuit 11 (that is, the threshold level of the switching transistor), the level of the control signal C can be adjusted when the negative level B exceeds a predetermined value. The switching transistor is configured to become small and control the switching transistor to turn off.

When this transistor is on, a switching signal D is generated to switch the transceiver into a transmitting state.

Furthermore, a squelch control signal generating circuit is provided which monitors the RF signal level and noise level of the receiving circuit 5 and generates a squelch control signal F, and the squelch gate circuit 6 is controlled by this control signal F.

In this structure, when there is a microphone input, the switching transistor of the transmission state switching signal generation circuit 11 is turned on by the detection signal A to generate the switching signal D, thereby putting the transceiver in the transmission state.

At this time, if the speaker is activated by a signal that has entered the receiving circuit for some reason, the speaker sound will be input to the microphone and oscillate, but at this time, the negative level from the anti-trip circuit's detector 9 Signal B is output to turn off the switching transistor and prevent the above-mentioned oscillation.

Furthermore, when the receiving circuit operates and there is a received signal, the negative level output B of the detector 9 similarly prevents the generation of the switching signal D, and prevents the microphone input from entering the transmitting state.

In this anti-trip circuit, since the smoothing capacitor of the rectifier circuit 9 is designed to have a large size so that the fall is delayed due to its function, the rise is inevitably delayed accordingly.

If there is no received signal when the transmit state switches to the receive state, the squelch gate of an FM transmitter closes due to its unique strong white noise and blocks the noise, but there is a received signal. The squelch gate is opened and transient noise is added to the speaker.

At this time, since the rise of the anti-trip circuit is slow, the anti-trip function is not yet activated.

Therefore, the transient noise causes a malfunction in which the microphone is excited and switched to a transmitting state.

Therefore, an object of the present invention is to provide a communication device such as a transceiver with an extremely simple structure that can prevent malfunctions caused by transient noise and can perform highly reliable switching operations.

The present invention will be explained below with reference to the drawings.

FIG. 2 is a circuit block diagram showing an embodiment of the present invention,
Parts equivalent to those in FIG. 1 are designated by the same reference numerals.

To explain the parts in the figure that are different from Figure 1,
Instead of the buffer amplifier 8, negative detector 9, and adder 10 as anti-trigger circuits, a switching circuit 13 is provided between the positive detector 4 and the switching signal generation circuit 11, and the switching circuit 13 is controlled to turn on and off. The squelch control signal F is used to control the squelch control signal F.

That is, a switching control signal generation circuit 14 is provided which receives the output F of the squelch control signal generation circuit 12 as an input, and this circuit has a squelch control signal F applied to its base, as shown in a specific example in FIG. A time constant circuit consisting of a transistor Q1, a resistor R1 and a capacitor G provided in parallel to its collector, a transistor Q2 to which the collector output is applied to the base, and a collector load resistor R2 of this transistor Q2. It includes;
A switching control signal G is output from the collector of the transistor Q2.

Note that the resistor R3 serves as a common emitter resistor for the transistors Q1 and Q2.

The operation of the circuit shown in FIGS. 2 and 3 will be explained using the operation waveforms of each part shown in FIG. 4.

The squelch control signal generating circuit 12 detects noise contained in the receiving circuit 5, and generates a squelch control signal F which becomes a low level when the noise level exceeds a predetermined value, and which becomes a high level when a receiving input is present. It can be seen that the relationship between the received signal waveform and the squelch control signal F is as shown in FIG.

Here, when the received signal arrives at time t2, the squelch gate control signal F becomes high level and the squelch gate 6
is opened and the signal drives the speaker via the amplifier 7.

At this moment, the transistor Q1 of the switching control signal generating circuit 14 is turned on and the transistor Q2 is turned off, so that the output G instantaneously rises to a high level in synchronization with the rise of the squelch control signal F.

This high level output G turns off the switching circuit 13 and prevents the rectified output A from being transmitted to the transmission switching signal generation circuit 11, thereby preventing malfunction due to transient noise and enabling normal anti-trip function during reception. becomes.

This state continues until t2, when the reception input disappears, the squelch control signal becomes low level, closes the squelch gate 6, and prevents noise generation from the speaker.

At this point, the transistor Q1 of the switching control signal generation circuit 14 is turned off, but the time constant circuit provided at its collector keeps the transistor Q2 in the off state.
The output G transitions to a low level after a delay of a period T determined by the time constant.

At this time, even if the received signal ends at time t2, the transmission switching circuit 11 may malfunction due to the output of the amplifier 1 due to room reverberation or self-vibration of the microphone, so in the conventional example, the fall of the anti-trip circuit is delayed. However, in this example, the generation period of the switching control signal G is made longer than the high level period of the squelch control signal F by T, thereby preventing such malfunction.

Therefore, the transmission state switching operation is possible only during the period t3 to t4, and the transceiver's anti-trip circuit and transmission/reception switching control can be performed using a simple circuit structure and having performance equivalent to or better than the conventional circuit shown in FIG. It becomes possible.

As described above, in the present invention, by simply adding a switching circuit and a switching control signal generation circuit, it is possible to reliably prevent malfunctions when switching from the transmission state to the reception state, and also to prevent malfunctions when switching from the transmission state to the reception state. By delaying the signal disappearance timing by a predetermined period of time, the switching from the receiving state to the transmitting state can be smoothly performed.

Furthermore, since it is possible to eliminate the conventional analog type anti-trip circuit, the circuit structure is simplified, which greatly contributes to miniaturization and cost reduction of the device.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional transceiver, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is a diagram showing an example of the switching control signal generation circuit of Fig. 2, and Fig. 4 is a block diagram showing an embodiment of the present invention. FIG. 3 is an operation timing diagram illustrating the circuit operation of FIG. 2; Explanation of symbols of main parts: 12... Squelch control signal generation circuit, 13... Switching circuit, 14... Switching control signal generation circuit.

Claims (1)

[Scope of utility model registration request] A communication device comprising squelch control signal generation means for generating a predetermined squelch control signal when a received signal is applied, and squelch gate means for making it possible to transmit the received signal to a speaker in response to the squelch control signal. , microphone input detection means for detecting microphone input and generating a detection signal;
a transmission state switching means that switches to a transmission state in response to the detection signal; and a switching signal that is generated in synchronization with the generation timing of the squelch control signal and that disappears after a predetermined period of time has elapsed from the disappearance timing of the squelch control signal. and a means for disabling the switching operation of the switching means during the generation period of the switching signal.