JPH02124652A - Signal multiplex circuit - Google Patents

Abstract

PURPOSE:To utilize each modulation index to the utmost and to improve S/N by modulating a pulse train so that the information of a picture signal is provided on a pulse frequency and the information of an audio signal is provided on a change in the pulse width respectively. CONSTITUTION:A base band picture signal is converted into a modulated pulse train by a PFM modulator (100% modulation) 2 an when the PFM modulation pulse is inputted to a monostable multivibrator circuit 3, the pulse is set at the leading and an output of the monostable multivibrator circuit 3 is given to a delay time variable pulse delay circuit 4, and the monostable multivibrator circuit 3 is reset by a prescribed delay signal. As a result, the PFM modulation pulse is subjected to pulse width modulation by the monostable multivibrator circuit 3. On the other hand, an audio signal from an audio signal input terminal 5 is FM-modulated by an FM modulator 6 and its delay time is changed at a pulse delay circuit 7 in response to the frequency of the FM signal. As a result, the PFM modulation pulse train is further subject to pulse width modulation by the audio signal and the audio signal is multiplexed on the PFM modulation pulse train. Thus, the S/N is not deteriorated and high quality transmission is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a first data signal (for example, two image signals) and a second data signal (for example, an audio signal) using a signal frequency modulation method ( The present invention relates to a signal multiplexing circuit used for transmission using a PFM modulation method (hereinafter abbreviated as PFM modulation method).

[Conventional technology]

Conventionally, for example, when multiplexing an audio signal onto two image signals,
As shown in FIG. 2, after the audio signal 5 is subjected to FM modulation (frequency modulation) by the audio signal FM modulator 6, the FDM multiplexing circuit 8 performs frequency division multiplexing (hereinafter referred to as FDM multiplexing) outside the band of the baseband image signal. ) to obtain multiplexed signals,
This multiplexed signal is converted into a frequency modulator (PFM modulator).
2 for pulse frequency modulation (PFM) and PF'M
It is output as signal 7.

[Problem to be solved by the invention]

By the way, in the conventional multiplexing system, the Noculus frequency modulator (
The usable dynamic range (generally limited to areas with good linearity) of the PFM modulator (hereinafter abbreviated as PFM modulator) is distributed by the ratio of the amplitude of the image signal to the amplitude of the audio FM carrier (abbreviated as AV ratio). There is.

Therefore, compared to the case where only two image signals or only two audio signals are transmitted, each modulation index is smaller, resulting in a decrease in VN.

Also, two image signals and audio FM carrier signal are simultaneously PF
Since it is M-modulated, if the non-linear distortion characteristics of the PFM modulator are poor, coupled wave distortion interference will occur, while if the audio FM carrier signal is subjected to multi-phase modulation by the image signal, it will become periodic noise. There is a problem that the so-called buzz ratio deteriorates.

SUMMARY OF THE INVENTION An object of the present invention is to provide a signal multiplexing circuit that can perform high-quality transmission without degrading performance.

[Means to solve the problem]

The signal multiplexing circuit of the present invention is a PF that modulates only two image signals.
I am trying to multiplex an M modulator (100% modulation), a mono multi circuit that uses the output pulse of the PFM modulator as input data, and a variable delay time delay circuit that determines the pulse width of the mono multi circuit. It is characterized by having a delay time control circuit that controls the delay time of the delay circuit in proportion to the amplitude of the input signal. The input signal to be multiplexed is a baseband audio signal (or data signal) or a carrier signal FM-modulated with the baseband audio signal (or a carrier signal FSK-modulated with the data signal).

〔Example〕

Next, the signal multiplexing method of the present invention will be explained using an example in which an image signal and an audio signal are multiplexed.

Referring to FIGS. 1 and 3, 1 is an input terminal for a baseband image signal. The baseband image signal is PF
The MFM modulator is converted into a modulated Noculus sequence. This modulated pulse train has a repetition frequency proportional to the amplitude of the input image signal and a constant pulse width. The PFM modulation pulse is input to the monomulti circuit 3. The mono multi circuit 3 is set at the rising edge of the PFM modulation pulse, and the output of the mono multi circuit 3 is given a predetermined delay by the pulse delay circuit 4 with variable delay time, and the mono multi circuit 3 is reset by this delay signal. be done. As a result, the PFM modulation pulse of the PFMFM modulator (the repetition frequency changes and the pulse width remains constant) is subjected to pulse width modulation by the monomulti circuit 3 (the repetition frequency remains unchanged and the pulse width remains constant). undergoing change).

On the other hand, the audio signal from the audio signal input terminal 5 is transmitted to the FM modulator 6.
The FM modulated signal (FM carrier) is input to a delay time delay circuit 7 of variable delay time type. The delay time of the pulse delay circuit 7 is changed according to the frequency of the FM signal.

The PFM modulated pulse train is further subjected to pulse width modulation by the audio signal, thereby multiplexing the audio signal onto the PFM modulated pulse train.

In the embodiment described above, the Nockle delay circuit 7 uses the FM modulated signal.
I tried changing the delay time.

The delay time of the /'P pulse delay circuit 7 may be changed using the audio signal itself.Furthermore, when multiplexing a data signal with an image signal, the pulse is changed using the data signal or an FSK' modulated carrier that is FSK-modulated with the data signal. The delay time of the delay circuit 7 may be changed.

〔Effect of the invention〕

As explained above, in the present invention, the pulse train is modulated so that the image signal has the repetition frequency of the pulse, and the audio signal has the respective information on the change in the width of the pulse. can be utilized to the maximum. Therefore, SA can be improved. Furthermore, as long as the Nockles width modulation circuit has no repetition frequency dependence, high-quality transmission is possible because no buzz beat is generated when the audio FM signal is subjected to multiphase modulation by the image signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a signal multiplexing circuit according to the present invention, and FIG. 2 is a block diagram showing a conventional example. FIG. 3 is a diagram showing an example of waveforms of each part of the signal multiplexing circuit shown in FIG. 1. 1... Image signal input section, 2... Pulse frequency modulator (PFM modulator), 3... Mono multi circuit, 4...
Variable delay time i4 Lux delay circuit 5...Audio signal input terminal. 6...Audio signal FM modulator 7...PFM signal output terminal.

Claims (1)

[Claims] 1 A signal multiplexing circuit for multiplexing a second data signal onto a first data signal, into which the first data signal is input, pulse modulating the first data signal and outputting a pulse frequency signal. a flip-flop circuit that is set by the pulse frequency signal and outputs a set signal; and a delay circuit that delays the set signal by a predetermined delay time and outputs it as a reset signal for the flip-flop circuit. characterized in that the delay circuit changes the delay time according to the second data signal, thereby multiplexing the second data on the pulse frequency signal by pulse width modulation. Signal multiplex circuit.