JP2537814Y2 - Squelch circuit - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The invention relates to improvement of an FM receiver and an FM radio having a scanning function and a monitoring function of a high priority channel when capturing a low priority channel. Things.

[Outline of the invention]

As a result of scanning, when a low-priority channel (hereinafter, CH-L) is being acquired, a high-priority channel (hereinafter, CH-H) is acquired.
That. ), Switch the channel to CH-H to check if the call is being made, return to CH-L if no call is made, and keep CH-H if the call is made I do. This function is called a high priority channel monitor function.

When implementing a high-priority channel monitor function with a single receiver, when a call is not being made on the CH-H and while switching the channel to CH-H (while checking the CH-H) , The sound receiving CH-L is interrupted.

In the present invention, the state before switching the channel from CH-L to CH-H is stored in RAM by the microcomputer, and when returning from CH-H to CH-L, the state of CH-L stored in RAM is returned. And CH-
By shortening the rise time of squelch at L,
This is to reduce the time during which the audio received by HL is interrupted.

[Conventional technology]

FIG. 3 shows a configuration of a squelch circuit in a conventional receiver. 1 is a detection signal input terminal from which an input signal of the receiver is detected. Basically, in the noise squelch circuit and the tone squelch circuit, the filter amplifier 2 is a high-pass filter and a band-pass filter.
Since the only difference between the output signal is when the output signal is ON and when the output signal is OFF is described below, the noise squelch circuit will be described below.

The high frequency component is amplified by the filter amplifier 2 and converted into a DC signal by the rectifier 3. Since the high-frequency component becomes unstable due to fading or the like, the DC signal is delayed by the delay circuit 7 so that the DC signal does not suddenly change. When the output signal of the delay circuit 7 is ON, that is, when a high frequency component exists, the switch 8 cuts off the received audio signal. The microcomputer 9 has a function of switching to a reception frequency suitable for the channel. Also, by reading the output signal of the delay circuit 7, it is possible to determine the presence or absence of an incoming call on the channel. Here, it is assumed that as a result of scanning the channel, the channel stops on the channel where there is an incoming call. If this stopped channel is CH-L, if there is a call on CH-H, CH
Performs high priority channel monitoring for the purpose of switching to -H.

 FIG. 4 shows the timing of the high priority channel monitor.

The microcomputer 9 starts the monitor timer when the receiving frequency is set to CH-L. When the monitor timer expires, switch to CH-H and start the check timer. When the check time has expired, the output signal of the delay circuit 7 is read, and when it is determined that there is no incoming call, the channel is switched to CH-L, the process returns to the process of starting the monitor timer, and the above is repeated.

Since the output signal of the delay circuit 7 is delayed by the time delayed from the filter amplifier 2 whose channel is switched as shown in FIG. 4 (b), the microcomputer 9 outputs the signal as shown in FIG. 4 (c). Is the switch while switching to CH-H
At 10 the received audio signal is stopped to prevent the noise on CH-H from being output. That is, the received voice signal returns to CH-L from the time of switching to CH-H, and is interrupted at the time shown in FIG. 4D until the output signal of the delay circuit 7 is turned ON.

[Problems to be solved by the invention]

The above-mentioned prior art has a drawback that the received voice signal is interrupted for a long time from returning to CH-L until the output signal of the delay circuit 7 is turned on, that is, as shown in FIG.

The present invention uses CH-L to shorten the interruption of the received audio signal.
It is intended to allow the received voice signal to pass immediately upon returning to.

That is, the purpose is to switch the received audio signal as shown in FIG.

[Means for solving the problem]

In order to achieve the above object, the present invention takes in the DC output signal of the rectifier 3 into a microcomputer 4 for controlling a channel, delays the DC output signal from the rectifier 3, and controls the switch 5 of the received voice signal.

FIG. 1 is a block diagram showing the overall configuration of the present invention.
Since the channel is controlled (switched) by the microcomputer 4,
The state in which the DC output signal of the rectifier 3 is delayed before the channel is switched to CH-H for the purpose of high-priority channel monitoring is stored in the built-in RAM of the microcomputer 4.
The state of delaying the DC output signal of the rectifier 3 is initialized by switching to, and the received voice signal is stopped by performing the delay operation. By setting the state previously stored in the internal RAM when returning to CH-L to the state in which the DC output signal of the rectifier 3 is delayed, the state returns to the previous state, and the switch 5 of the received voice signal operates as if the channel Is controlled as if it were not switched.

[Action]

As a result, when the received audio signal is ON in CH-L before switching to CH-H, the received audio signal when returning from CH-H to CH-L is turned ON. Conversely, when the front is OFF, O
Become FF. This timing is shown in FIG.

〔Example〕

FIG. 2 shows a flowchart of an embodiment of the present invention, which will be described below. As a result of the scan, when the signal is held at CH-L, the priority monitoring process shown in FIG. 2 is executed. The monitor timer is a timer that measures the time for operating in CH-L. Until the monitor timer expires, the received audio signal (hereinafter referred to as AF) is controlled by the SQ timer. That is, the DC signal of the rectifier 3 is read, the delay is performed by the SQ timer, and the switch 5 is turned ON or OFF according to the result.

When the monitor timer expires, the contents of the SQ timer are
And then switch the channel to CH-H. next
Initializes the SQ timer so that AF stops.

The check timer is a timer that measures the time that the CH-H operates. Until the check timer expires
Performs AF control using the SQ timer. If there is no incoming call, A
F is muted (that is, the switch 5 is OFF).
Conversely, if there is an incoming call, the AF is unmuted, the high priority channel (CH-H) monitoring process ends, and the process transits to the CH-H reception process.

When the AF is muted, the channel is switched to CH-L (that is, return), and the previous channel stored in RAM
Set the contents of the SQ timer in -L to the SQ timer, and repeat this from the start of the monitor timer and execute it.

In this embodiment, an AF control process by the SQ timer, a process of transferring the contents of the SQ timer to the RAM and saving, and a process of transferring the content from the RAM to the SQ timer are added.

The functions of the conventional delay circuit 7 and switch 8 are configured by AF control by the SQ timer, and the contents (or state) of the SQ timer are stored in RAM, so that the SQ after returning to the CH-L can be used. The operation of the timer is continued from the previous state of CH-L. As a result, if AF is muted in the previous CH-L, the returned CH-L is also muted if AF is muted, and conversely, if AF is muted, the returned CH-L is also muted. AF is interrupted when there is an incoming call.
F is unmuted, and AF is turned on as shown in Fig. 4 (e).
Is interrupted. In the above, CH-L to CH-H and CH-L
Although the description has been given of the case of channel switching returning to the above, some apparatuses may perform transmission and reception in which transmission and reception are alternately performed. In this case, after receiving for a certain period of time, the apparatus goes into the transmission state, and then returns to the reception state. When returning to this reception state, if the above-described means is provided, the sound is not interrupted (for example, start-up of reception), and the effect is large.

That is, when changing to a predetermined specific reception state such as channel switching or transmission / reception switching, the reception state (reception mode) before each change is stored, and when returning to the immediately previous state after the change, Instead of determining and returning the state of the delay signal of the squelch circuit, the state immediately returns to the reception state based on the stored contents.

[Effect of the invention]

According to the present invention, the delay circuit 7 and the switch 8 which are conventionally required are not required, and the microcomputer 4 can realize those functions instead. Further, as described above, the interruption of the received audio signal generated when monitoring the high priority channel can be reduced from FIG. 4D to FIG. 4E.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of the present invention, FIG. 2 is a flowchart showing an embodiment of the present invention, FIG. 3 is a block diagram showing the conventional overall configuration, and FIG. It is a timing chart at the time. 1: detection signal input terminal, 2: filter amplifier, 3: rectifier, 4: microcomputer, 5: switch, 6: received audio signal output terminal, 7: delay circuit, 8: switch, 9: microcomputer, 10: switch.

Claims (1)

(57) [Scope of request for utility model registration] 1. A microcomputer for controlling a switch of a received audio signal, a filter amplifier for amplifying a high frequency component of a detection signal, and a rectifier for converting an output signal of the filter amplifier into a DC signal. The microcomputer takes in the output signal of the rectifier, delays the output signal of the rectifier, controls the switch of the received audio signal by the output signal of the delayed rectifier, and the delay in the channel L before switching the channel. After storing the signal or the delay state in the memory,
A microcomputer-controlled squelch circuit having a function of controlling a switch of the received audio signal based on a delayed signal or a delay state previously stored in a memory when switching to channel H or transmission and then returning to channel L. .