JP2754897B2 - Demodulator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a demodulation circuit for a modulated baseband control signal.

〔Overview〕

The present invention provides a means for demodulating a control signal obtained by modulating a main signal into a baseband signal. By determining the level of the baseband signal by detecting the rise and fall of the control signal, the signal can be demodulated based on the SN ratio of the signal. In this way, it is possible to prevent the reception width from being restricted.

[Conventional technology]

In the conventional example, as shown in FIG. 3, a modulated baseband control signal is detected by a filter 2 and a rectifier circuit 4 is detected.
The magnitude of the amplitude obtained through is identified by the comparator 7.

[Problems to be solved by the invention]

In such a conventional example, in the case of amplitude modulation, if the amplitude of the main signal changes, the control signal also changes, and if the noise crosses the threshold value of the comparator, the control signal cannot be reliably demodulated. Also, when the control signal becomes small and the high level of the signal becomes smaller than the threshold value of the comparator,
The control signal cannot be demodulated. In addition, when the control signal increases, the noise component also increases and crosses the threshold value of the comparator, so that it is impossible to reliably demodulate the command. That is, when the threshold value of the comparator is set,
There is a drawback that the reception width that can be demodulated is limited by the SN ratio of the signal.

The present invention eliminates such drawbacks and reduces the signal
It is an object of the present invention to provide a demodulation device in which a reception width that can be demodulated by an SN ratio is not limited. [Means for Solving the Problems] The present invention has a frequency different from the frequency of a main signal and is smaller than the amplitude of the main signal. A filter that passes the signal superimposed on the main signal among the modulated signals whose amplitude signal is superimposed on the main signal for the duration of one value of the binary control signal, and rectifies the signal output from the filter. In a demodulation device including a rectifier circuit and a comparator that identifies the amplitude of a signal output from the rectifier circuit, a preprocessing unit that generates a signal corresponding to a rising part and a falling part of a signal output from the rectifier circuit is provided. Wherein the comparator comprises:
It has two thresholds, outputs a signal of a first predetermined level when the value of the rising part of the signal reaches one of the thresholds, and sets the value of the falling part of the signal to the other value of the threshold. It is characterized in that a signal of a second predetermined level is output when the signal reaches.

Here, it is preferable that the pre-processing means includes an integrating circuit for integrating a signal output from the rectifying circuit and a differentiating circuit for differentiating a signal output from the integrating circuit.

[Action]

The control signal component extracted from the modulation signal and rectified,
The signal indicating the rising portion and the falling portion of the signal component is generated by performing integration processing and differentiation processing. The comparator compares the two signals with two thresholds to determine an intersection, and outputs a signal having the intersection as a change point of the signal level.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

 FIG. 1 is a block diagram showing the configuration of this embodiment.

That is, in this embodiment, as shown in FIG. 1, a signal having a frequency different from the frequency of the main signal and having an amplitude smaller than the amplitude of the main signal is applied to the main signal for the duration of one value of the binary control signal. A filter 2 for passing a signal superimposed on the main signal among the modulated signals superimposed on the filter 2, a rectifier circuit 4 for rectifying a signal output from the filter 2, and an amplitude of a signal output from the rectifier circuit 4 And a pre-processing means for generating a signal corresponding to a rising portion and a falling portion of the signal output from the rectifier circuit 4 as means characterized by the present invention. When the value of the rising portion of the signal reaches one of the threshold values, a signal of a first predetermined level is output, and the value of the falling portion of the signal reaches the other value of the threshold value. Then the second Predetermined level is configured for outputting a signal, comprising a differentiating circuit 6 for differentiating the output signal of the integration circuit 5 and the integrating circuit 5 integrates a signal output from the rectifier circuit 4.

 Next, the operation of this embodiment will be described.

The control signal extracted by the filter 2 is rectified by the rectifier circuit 4 to become a baseband signal. This is detected by the integration circuit 5 and the differentiation circuit 6 at the rise and fall of the baseband signal. Next, the connected comparator 7 has a hysteresis characteristic, and the output of the comparator 7 switches between the high level and the low level only when the output of the differentiating circuit 6 detects the rise and fall of the baseband signal. In this case, the output of the comparator 7 does not change.

 This will be described with reference to FIG.

(1) is a modulation signal to be input, (2) is a control signal extracted by a filter, and (3) is a rectified waveform thereof. The rectified waveform has a noise component due to the main signal and other effects. This is integrated by the integration circuit 5 (4).
(5) is further differentiated by the differentiating circuit 6, and the rise and fall of the control signal are detected. Comparator 7
Has a threshold value, the output of the comparator 7 goes high when a rising signal is detected, and goes low for a falling signal to obtain (6).

〔The invention's effect〕

As described above, according to the present invention, the rise and fall of the rectified baseband control signal are detected by the integration circuit and the differentiation circuit, and the comparator is provided with hysteresis. There is an effect that can be done.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. FIG. 2 is a waveform chart showing waveforms at various parts in FIG. FIG. 3 is a block diagram showing a configuration of a conventional example. 1 ... control signal modulation input terminal, 2 ... filter, 3 ...
Amplifier 4, rectifier circuit 5, integrating circuit 6, differentiating circuit 7, comparator 8, control signal demodulation output terminal.

Claims (2)

(57) [Claims] 1. A modulation signal superposed on a main signal having a frequency different from the frequency of the main signal and having an amplitude smaller than that of the main signal for a duration of one value of the binary control signal. A demodulator comprising: a filter for passing a signal superimposed on the signal; a rectifier circuit for rectifying a signal output from the filter; and a comparator for identifying an amplitude of a signal output from the rectifier circuit. A preprocessing means for generating signals corresponding to a rising portion and a falling portion of the output signal, wherein the comparator has two thresholds, and when the value of the rising portion of the signal reaches one of the thresholds, A signal of a first predetermined level, and a signal of a second predetermined level is output when the value of the falling part of the signal reaches the other value of the threshold value. Demodulator. 2. The demodulator according to claim 1, wherein said preprocessing means includes an integrating circuit for integrating a signal output from said rectifying circuit and a differentiating circuit for differentiating a signal output from said integrating circuit.