JPH02141141A - Multiplex-demultiplex transmitter for pulse-processing fm and pwm signal - Google Patents

Abstract

PURPOSE:To attain the multiplex transmission in which 3 or above signals are subjected to pulse frequency modulation and pulse width modulation by applying pulse width modulation to FM signals subjected to pulse processing alternately. CONSTITUTION:An input signal 101 is converted into an FM signal 104 by an FM modulator 1. An identification voltage of the FM signal is changed by a 2nd input signal 102 and the result is identified by a comparator 4. Thus, an output from the comparator is an FM signal pulse 107 whose pulse width is modulated by a 2nd signal. Similarly, the FM signal is an FM signal 108 subjected to pulse width modulation by using a 3rd input signal 103. Then the FM signal is differentiated by a differentiating circuit 2, a waveform 106 is obtained and the signal is used as a clock to operate a 1/2 frequency divider 3. A switch 6 is changed over by using a pulse having the waveform 106 subjected to frequency division and a pulse processing FM signal subjected to pulse width modulation is outputted alternately. The output is a multiplex signal 109.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a transmission device that performs pulsed analog modulation of a wideband signal such as a video signal, pulse width modulates it with another signal, and multiplexes and transmits a plurality of signals. It is.

2. Description of the Related Art A conventional device related to a method of multiplexing PWM modulation onto a pulsed FM signal and transmitting the signal includes, for example, the one shown in FIG. (Study of optical multiplex transmission system of P-FM and PWM, Okamura; et al.
294) The video signal input to Video In of the transmitter is converted into a pulsed FM signal by the modulator 51.

This pulsed FM signal is converted into an FM signal after passing through the BPF 52 and is input to the multiplexing section. On the other hand, Data
The data input to In is converted to (7, 4) by the encoder 55.
After being Hamming encoded, the signal is subjected to FSK by a modulator 51, passes through a BPF 56, and is input to a multiplexing section. This multiplexer uses the FSK data as a threshold to identify FM waves in the video signal. Therefore, the pulse width of the pulsed FM is modulated by the FSK signal. Thereafter, it is converted into an optical signal by an E10 conversion 54 and sent out. Waveform 107.1
The shaded portion at 08 is the portion subjected to pulse width modulation.

FIG. 6 shows another conventional example of a multiplexing system for pulsed analog signals. (Proposal of HDTV signal optical transmission system using pulse frequency/width modulation, Morikura et al., Koba 1963 IEICE Information Zenzennin D-707) Figure 7 shows the waveforms of each part. On the transmitting side, the Y signal whose band is limited by the LPF 61 and the emphasis 62 is removed is converted into a PFM signal θ01 by the modulator 63. The PFM signal is divided in half by a division period 68, and two sawtooth wave voltage generators 69 and 70 having a phase difference of 180' generate two sawtooth waves. A comparator 71 compares this sawtooth voltage with the PR and PB double signal amplitudes band-limited by the LPF 67.68.
．． 72, and when the two match, a trigger pulse is output. A PFM-PWM multiplexed signal 605 is created by setting and resetting the R8-FF 64 using the added signal of the trigger pulse and the original PFM signal. Thereafter, the laser drive circuit 65 is operated to convert the signal into an optical signal. The shaded portions of waveforms 107 and 108 are the portions subjected to pulse width modulation.

FIG. 8 shows a spectrum when PFM and PWM are multiplexed. A spectrum 801 in the low range of the PFM pulse for the first input signal, a spectrum 802 of the PWM signal for the second input signal, and a PW for the third input signal.
The spectrum 803 of the M signal overlaps with the spectrum 803 of the M signal. Therefore,
In order to separate these signals, it is necessary to do it on the time axis, and it is not possible to separate them on the frequency basis.

FIG. 9 shows an explanatory diagram showing interference between pulses.

The front and rear pulses are the same on the solid line.

However, when two pulses approach each other, the latter pulse is influenced by the previous one, causing the pulse to be deformed as shown by the broken line.

In PWM modulation, information is carried in the pulse width, and different information is carried in alternating pulses, so when the width of the following pulse changes depending on the previous pulse, the second and third signals
Interference with other signals occurs.

Problems to be Solved by the Invention As explained above, conventional devices cannot multiplex three or more input signals. Furthermore, even when multiplex transmission is possible, there is a drawback that interference between signals is large.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides that the first signal is
M modulation is performed, and by changing the slice level of the output of the FM modulator with the second signal, the pulse width modulated pulse and the FM signal are alternately output at the peak position for multiplex transmission.

Function: According to the present invention, the second and third signals can be multiplexed and transmitted by alternately pulse width modulating the pulses of the pulsed FM signal. In addition, the pulsed FM signal has the same demodulated S
Since the pulse interval can be set large for the PFM signal for obtaining /N, interference between pulses can be reduced, and as a result, crosstalk between signals can be reduced.

Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

An input signal 101 is converted into an FM signal converter 04 by an FM modulator 1. The identification voltage of this FM signal is input to the second input signal 102.
is changed and identified by comparator 4.

Therefore, the output from the comparator is a pulsed FM signal 107 whose pulse width is modulated by the second signal.

Similarly, the FM signal becomes a pulsed FM signal 108 that is pulse width modulated with the third input signal 103.

On the other hand, the FM signal is differentiated by the differentiating circuit 2 to form a waveform 106, and the frequency divider 3 is operated using this signal as a clock. The switch 6 is switched by the pulse of the frequency-divided waveform 106, and the pulsed FM is subjected to the pulse width modulation described above.
Output signals alternately. This is the multiplexed signal 109.

FIG. 3 shows an embodiment of the demodulator. Before showing an example, a signal spectrum will be explained briefly. FIG. 4 shows the spectrum of a pulsed FM signal subjected to pulse width modulation. As shown in the figure, since the pulsed FM signal 401 does not have a low-frequency component, the spectrum of the pulsed FM signal, the second signal spectrum 402 subjected to pulse width modulation, and the third signal spectrum 403 exists in a different frequency band. Therefore, the PFM signal can be separated by a filter. The demodulator uses this property to separate the FM and PWM components. Further, the PWM signal is separated into alternating pulses, and then each signal is separated using a low-pass filter and a bandpass filter. Here the third
The case where a band signal is used as the signal has been described, but in the case of the base band signal, it is demodulated by a low-pass filter.

By the way, the pulse waveform of the transmitted pulses is distorted and attenuated due to band limitations in the transmission path and the like. The input signal 301 is amplified to an appropriate voltage by the amplifier 7, and the differential circuit 8
The rising and falling edges of the pulse are detected, and the pulse reproducing circuit 9 reproduces the original pulse using this differentiated pulse.

When the reproduced pulse is input to the bandpass filter 10, F
M signal is reproduced. When this FM signal is subjected to pulse delay detection, a first signal 302 is demodulated.

On the other hand, the FM signal is differentiated by the differentiating circuit 12, the 2 frequency divider 13 is operated at the rising edge of the FM signal, and the selector 14 is operated by the frequency divided output to generate a pulsed FM signal that has undergone pulse width modulation.
Outputs pulses alternately.

When the pulse width modulated pulse is passed through a low pass filter 15, a second signal is demodulated.

On the other hand, the output 15 that has passed through the bandpass filter 16 is the third
becomes the signal 304.

In this embodiment, a band signal is used as the third signal. Therefore, even when pulsed FM and PWM are multiplexed, the spectra are separated. Therefore, the second and third signals are separated both in frequency and time, so crosstalk is small.

It is obvious that the same effect can be obtained even if the second, third, and third signals are respectively band signals and the frequency bands are changed.

Further, as shown in FIG. 9, when a pulse with a constant pulse width is generated from both the rising and falling edges of the pulsed FM signal, a PFM signal with twice the frequency is generated. Therefore, in order to obtain the same demodulation S/N, the pulsed FM signal only needs to have one-half the band of the PFM signal. Therefore, the pulse interval is twice that of the PFM signal. 90 in Figure 9
As shown in Fig. 1, as the pulse interval increases, the interference between the pulses becomes smaller. Therefore, the pulsed FM signal has a higher PF'
Crosstalk between PWM signals can be made smaller than that of the M signal.

In addition, in this example, PWM modulation was performed using two signals, but N
It is clear that if N+1 signals are PWM modulated, a total of N+1 signals can be multiplexed and transmitted.

Effects of the Invention As described above, according to the present invention, multiplex transmission of three or more signals by pulse frequency modulation and pulse width modulation can be performed, and crosstalk between the signals can be reduced.

[Brief explanation of the drawing]

Figures 1 and 3 are configuration diagrams of an embodiment of the present invention, Figure 2,
FIG. 4 is a waveform diagram for explaining the present invention in detail, FIGS. 5 and 6 are configuration diagrams showing conventional embodiments, and FIGS. 7, 8, and 9 are for explaining the operation. FIG. 1...FM modulator, 4...first comparator, 5...
2nd comparator, 6... switch, 3... differentiator,
3... Frequency divider, 10... Band pass filter, 11
...FM demodulator, 9...Pulse regeneration circuit, 14...
・Pulse separation circuit, 15.16...PWM demodulation circuit,
8... Differential circuit. Name of agent: Patent attorney Shigetaka Kurino Haka18 ILL No. 3 Fig. 2 Fig. Fig. Daτ et al. Fig. Fig.

Claims (6)

[Claims] (1) an FM modulator that performs FM modulation on a first signal; a first voltage comparator that changes the identification level with a second signal to identify the output of the FM modulator; and a third voltage comparator that identifies the output of the FM modulator with a third signal; a second voltage comparator that changes the level to identify the output of the FM modulator; and a voltage comparator between the first voltage comparator output and the second voltage comparator near the peak position of the output of the FM modulator. 1. A multiplex transmission device for pulsed FM and PWM, comprising a switch for switching output. (2) The output switch is comprised of a differentiating circuit that takes the differential of the output of the FM modulator, and a T-type flip-flop circuit that is inverted by a positive or negative pulse of this differentiating circuit. A multiplex transmission device for pulsed FM and PWM according to claim 1. (3) an FM modulator that performs FM modulation on the first signal;
1 (N is a positive integer) signal to change the discrimination level to identify the output of the FM modulator, a total of N voltage comparators up to the Nth voltage comparator; Pulsed FM and P, characterized by comprising a switch that sequentially switches the output of the Nth voltage comparator.
Multiplex transmitter with WM. (4) an FM modulator that performs FM modulation on a first signal; a first voltage comparator that changes the discrimination level with a second signal to identify the output of the FM modulator; a second voltage comparator that identifies the output of the FM modulator by changing the discrimination level with a third signal in a different frequency band; 1. A multiplex transmission device for pulsed FM and PWM, comprising a switch that switches between a comparator output and the second voltage comparator output. (5) a pulse regeneration circuit for regenerating pulses from a received signal in which a pulsed FM signal and a PWM signal are multiplexed; a bandpass filter for separating the FM signal; and a bandpass filter for separating the FM signal. an FM demodulator that demodulates the output, a pulse separation circuit that alternately separates and outputs the reproduced pulses, and two PWM demodulation circuits that pass the separated outputs through a low-pass filter to demodulate the PWM modulated signal. Pulsed FM and PWM characterized by consisting of
and demultiplexing receiver. (6) The pulse regeneration circuit regenerates pulses using a differentiating circuit that creates a differential of the received signal and a flip-flop that sets a flip-flop circuit with a positive direction pulse of the differentiator circuit and resets the flip-flop circuit with a negative direction pulse. 6. The pulsed FM and PWM multiplexing/demultiplexing receiving apparatus according to claim 5, comprising a circuit.