JPS584858B2 - Pulse Habahenchiyouchiyuukeiki - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a repeater that regenerates and repeats simple multilevel digital pulse width modulation signals in digital transmission using coaxial cables, optical fiber cables, or carrier waves.

Conventionally, a pulse width modulation repeater has been used in a communication system that takes a positive integer n as a multi-value, converts information into n pulse widths, and sends a signal.

Conventional pulse width modulation repeaters utilize pulse generators that generate signals with different pulse widths depending on the sign of the input signal.

Fluctuations in the width of the pulse generator's output pulses degrade transmission quality, so the pulse generator required numerous adjustments and a complex circuit configuration in order to keep the pulse width within a specified value.

In order to eliminate these drawbacks, the present invention uses the same pulse generator to generate pulses with the same pulse width corresponding to each discrimination level, and then adds those pulses on the time axis. It is designed to obtain pulses with different pulse widths, and its purpose is to simplify the pulse width modulation repeater.

FIG. 1 shows an embodiment of the present invention, which is applied to optical communication.

If the multi-value is 3-valued, the codes are “0”, “1”, “2”
On the other hand, the optical pulse corresponds to a constant amplitude signal with a different pulse width smaller than the pulse repetition period T, as shown in FIG. 3A.

In other words, code “0” means no pulse, code “1” means pulse width τ
A signal of 1, code "2" corresponds to a signal of pulse width τ2.

Furthermore, as shown in this figure, the rises of the pulses in each cycle are aligned at the same point in time.

To simplify the explanation, a light emitting element 1 such as a light emitting diode or a semiconductor laser as an output stage in FIG.
It is assumed that the waveform of the output optical signal 12 of No. 1 is as shown in FIG. 3A.

This optical signal output 12 is applied, for example, to an optical fiber (optical glass fiber) diagram (not shown) and reaches the photodiode 2 of the next repeater as signal input 1.

One end of the photodiode 2 is connected to the bias power supply terminal VB, and the other end is grounded through the load resistor 16.

The signal 1 that has been photo-electrically converted by the photodiode 2 is passed through the amplifier 3 and the waveform shaping circuit 4, and is amplitude-modulated according to the pulse width as shown in FIG. 3B. The waveform is shaped.

That is, the waveform has a 0 level for no pulse, a 1 level for a pulse of τ1, and a 2 level for a pulse of τ2.

On the other hand, a part of the output of the amplifier 3 is branched and applied to the timing extraction circuit 5, where a clock having a clock frequency f (f=1/T) is extracted.

As the timing extraction circuit 5, a single tuning circuit or a phase-pull oscillator, which has been commonly used in the past, can be used.

The output of the waveform shaping circuit 4 is branched to discriminators 6a and 6.
added to b.

The discrimination level is a level l1 between the 0 level and 1 level in the discriminator 6a, and 1 in the discriminator 6b.
Each level is set to level 12, which is intermediate between level 2 and level 2.

The clock signal output from the timing extraction circuit 5 is passed to the discriminator 6.
At each of the discrimination levels a and 6b, the discrimination operation is set to be performed at time points t1 and t2, respectively, when the eye opening of the eye pattern of the received waveform shown in FIG. 3B becomes maximum.

Pulse generators 7a and 7b are driven by the clock from circuit 5 in accordance with the outputs of these discriminators 6a and 6b, respectively.

These pulse generators 7a and 7b have the same pulse width τ1
pulses are generated respectively.

The pulse generators 7a and 7b can be easily realized using a circuit such as a mono-multi-by-break circuit.

The outputs of the pulse generators 7a and 7b are logically summed with each other with relative time shifts within the range of the pulse width τ1.

In this example, the output of the pulse generator 7b is delayed by τ1 in the delay circuit 8, and the delayed signal F and the output of the pulse generator 7a are
The output E and the output E are logically summed in a circuit 9.

Therefore, when the code "0" is received, the received waveform becomes the "0" level, and neither of the discriminators 6a and 6b generates a pulse, the outputs E and F are 0, and the output of the circuit 9 is also 0.

When the code “1” is received, the converted amplitude modulation signal is “1”.
” level, and only the discriminator 6a generates a pulse.

Therefore, the output E becomes a pulse with a pulse width τ1, the output F is 0, and the output of the OR circuit 9 becomes a pulse with a width τ1.

When the code "2" is received, a pulse is generated in both the discriminators 6a and 6b, so the outputs E and F are both pulses with a pulse width τ1, and the circuit 9 outputs a pulse with a pulse width τ2 (=τ1+T1).
) pulse is generated.

The output pulse of the OR circuit 9 is amplified by an amplifier 10 and then applied to a light emitting element 11, from which an optical signal waveform is reproduced and emitted as an output optical signal 12.

FIG. 2 shows another embodiment of the discrimination regenerator, in which a discriminator 6 and a pulse generator 7 are integrated.

That is, the output of the waveform shaping circuit 4 is applied to the data terminal D of the D-type flip-flop 13, which is read and identified at a predetermined time by the clock of the circuit 5, and the identification result is produced at the output terminal Q. .

The clock from circuit 5 is delayed through delay circuit 14 to reset flip-flop 13.

Therefore, the delay circuit 1 is connected to the output terminal Q of the flip-flop 13.
A pulse with a pulse width determined by the delay time of 4 is generated.

With this configuration, the pulse generator can be configured very easily, which has the advantage of being excellent in mass production.

As explained above, according to the pulse width modulation repeater of the present invention, pulses with different pulse widths are synthesized only by a pulse generator with the same pulse width and a delay circuit, so that mass productivity is excellent during manufacturing. ing.

The above explanation was for the case where a three-value pulse width modulation repeater was configured in which the pulse rise times were aligned at the same time.
Three or more values can be constructed in exactly the same manner, and the present invention can also be applied to a multi-value pulse width modulation repeater in which the falling points of the pulses are aligned at the same time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a pulse width modulation repeater according to the present invention, FIG. 2 is a block diagram showing an example of an identification reproducing circuit thereof, and FIG. It is an eye diagram. 1: Optical signal input, 2: Photodiode, 4: Waveform shaping circuit, 5: Timing extraction circuit, 6a, 6b: Discriminator,
7a, 7b: pulse generator, 8: delay circuit, 9: OR circuit, 11: light emitting element, 12: optical signal output, 13: D type flip-flop with set/reset, 14: delay circuit.

Claims (1)

[Claims] 1 An n-value (a positive integer of n≧3) digital multi-value pulse width modulation input signal is supplied, and an identification pulse with the same pulse width τ1 is output for each input equal to or higher than the set level.
- comprising one discriminator, means for shifting the relative time positions of these discrimination output pulses within the range of the pulse width τ1, and an OR circuit for calculating the logical sum of these mutually shifted discrimination outputs. Pulse width modulation repeater.