JPS6255738B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tone signal detection device for obtaining a tone squelch or a control tone for an FM radio, etc., using a prewave detector or a bandpass wave detector.

Conventionally, this type of signal detection device was developed, for example, in
-93902, and as shown in Figure 1, there is a fixed cut-off frequency prewave circuit 2, an amplitude limiting amplifier 3, and a band in which the center frequency can be set in accordance with the desired detection frequency of tone signals, etc. It consists of a pass wave device 4 and a wave detector 5. If the desired detection frequency range is from _OMIN to _OMAX as shown in Figure 2, the cutoff frequency _c of the prewave device 2 must be selected higher than _OMAX . , and since it is fixed, the signal band other than the desired signal including noise is at this fixed cutoff frequency.
If it extends to a frequency lower than _C , there is a drawback that the desired frequency sequence _OMIN to _OMAX is uniformly suppressed by the amplitude limiting amplifier 3 by a signal other than the desired wave.

FIG. 3 shows another conventional example, in which both the prewaver 7 and the bandpass waver 8 are clock-controlled waveformers that can be selected from sample data filters (e.g., switched capacitor filters, transversal filters) or digital filters. This is an example of using a double-capacitor filter, and includes a prewave generator 7 consisting of a clock-controlled waveform with a fixed cut-off frequency, an amplitude limiting amplifier 3, a bandpass waveform 8 consisting of a waveform with a clock-controlled variable center frequency, and a wave detector 5. , reference signal generation circuit 9 for clock generation, fixed frequency divider 1
0 and a variable frequency divider 11. In this configuration, compared to the one in FIG. 1, the center frequency _O of the bandpass filter 8 can be easily changed by controlling the clock obtained from the variable frequency divider 11 using the desired frequency setting terminal 12. However, since the band waver 8 is a clock-controlled waver, there is a clock return response (eg, 5KHz if the sample clock is 10KHz). This can be prevented by limiting the frequency range of the input signal 1 using the presynchronizer 7, but in this case, in the configuration shown in FIG _.
The cutoff frequency of the presocket is constant over _OMAX , and the cutoff frequency is determined by _OMAX . Therefore, the lower limit of the clock frequency of the band waver 8 is such that its feedback response is equal to the lower limit of the clock frequency of the band waver 8.
It is limited to a point where it is sufficiently attenuated. _OM
There is a drawback that an unnecessarily high band frequency clock must be used when receiving a desired wave below _AX .

The present invention provides a device that eliminates these drawbacks by making it possible to use the optimum cut-off frequency of the prewaveform generator and the clock frequency of the bandpass waveformer over the entire frequency range _OMIN to _OMAX of the desired wave. An example of this will be described below with reference to the drawings.

FIG. 4 shows an embodiment of the present invention,
1 is an input signal such as a tone signal 16 is a variable cut-off frequency prewaver, 3 is an amplitude limiting amplifier, 8 is a variable center frequency band waver, 5 is an amplitude detection type detector circuit, 6 is a detection output, 9 is a Reference signal generation circuit, 17
11 is a variable frequency divider (frequency division ratio m), 11 is a variable frequency divider (frequency division ratio n), and 12 is a desired wave frequency setting terminal.

The operation will be explained below.

The input signal 1 is band-limited by the prewave generator 16, which uses a clock-controlled wave generator, and this clock controls the signal from the reference signal generation circuit 9 to set the desired wave frequency. terminal 12
The frequency is divided by a variable frequency divider (frequency division ratio m) 17 controlled by . Therefore, the cutoff frequency of the prewave unit 16 is controlled according to the desired wave frequency, and the optimum band limit is applied to the set desired wave frequency, and its output is controlled to prevent malfunctions due to noise and to ensure a level margin. Amplitude limiter 3 provided
sent to. The amplitude-limited signal enters the band-pass waver 8, but this waver 8 also uses a clock-controlled waver, and this clock transfers the signal from the reference signal generation circuit 9 to the desired wave frequency setting terminal 12.
The frequency is divided by a variable frequency divider (frequency division ratio n) 11 controlled by . At this time, since the input signal has already been band-limited by the prewaver 16, the frequency division ratio can be set to m<n. Furthermore, the output signal of the band-pass wave detector 8 passes through the wave detector 5 and becomes a detection output 6.

By setting the desired wave frequency setting terminal 12 in this way, the cutoff frequency ( _CMIN to _CMAX ) of the prewave generator 16 and the center frequency ( _OMIN to _OMAX ) of the bandpass wave generator 8 are changed, so that it can be used over a wide range. Optimal band limiting is possible over the desired wave frequency range, and as a result, malfunctions caused by signals other than the desired wave are reduced. As an example, since an appropriate band limit is applied, it is possible to use the minimum necessary frequency for each desired signal as the clock frequency for the bandpass waveform generator, and the division ratio of the clock frequency for the bandpass waveform waveform generator is As n becomes larger, accuracy becomes easier. Furthermore, as is well known, the reduction in clock frequency has advantages such as a reduction in the number of delay stages and a reduction in the capacity ratio in terms of the structure of the clock control waveform, and its industrial value is great.

[Brief explanation of the drawing]

1 and 3 are block diagrams of a conventional signal detection device, FIG. 2 is a diagram showing the frequency relationship of the device in FIG. 1, and FIG. 4 is a block diagram of a signal detection device in an embodiment of the present invention. FIG. 5 is a diagram showing the frequency relationship diagram. 16... Pres waver, 3... Amplitude limiting amplifier,
8... Bandpass wave generator, 5... Detection circuit, 9...
Reference signal generation circuit, 17... variable frequency divider, 11...
...variable frequency divider.

Claims (1)

[Claims] 1 An amplitude-limiting amplifier and a wave detector are provided, and a clock-controlled prewave circuit whose cut-off frequency changes in accordance with the tone frequency to be detected is provided before the amplitude-limiting amplifier, and a detection device is provided after the amplitude-limiting amplifier. 1. A tone signal detection device comprising a clock-controlled bandpass converter whose center frequency changes in accordance with the tone frequency to be detected.