JPS6038905B2 - Timing signal extraction circuit - Google Patents

Description

[Detailed description of the invention] A differential phase modulation wave (
In the synchronous detection circuit of the received carrier (hereinafter referred to as the received carrier), one phase information is formed - detecting that phase information at the position where intersymbol interference is least in the time slot is an important factor that determines the characteristics of the detection circuit. It is.

Therefore, the timing signal that determines the detection position of the time slot needs to be of high quality. The present invention relates to a timing signal extraction circuit that extracts this timing signal. Conventionally, the difference signal between both sideband waves of the received carrier was used, and the timing signal was created using the change point of the demodulated baseband signal (Reference:
Data transmission circuit Nikkan Kogyo Shimbun Tatsuhiko Hayashi et al. 2 authors P91~
P98).

The timing signal created by the former method has the following drawbacks. When the receiving carrier passes through the carrier line, both sideband waves of the receiving carrier are affected by group delay distortion, so the difference signal of the both sideband waves changes its phase, and the timing signal created from the difference signal is As a result, the position at which time slot phase information is detected is changed. Timing signals created by the latter method had the following drawbacks. If the received carrier has only certain phase information, there will be no changing points in the demodulated baseband signal, and as a result, a timing signal cannot be obtained. SUMMARY OF THE INVENTION An object of the present invention is to provide a timing signal extraction circuit that solves the above problems.

The present invention is a timing signal extraction circuit that detects a received carrier every other time slot and extracts a timing signal.

Generally Q. It is known that by multiplying a phase modulated wave having a phase change of =360o/2n by n, a signal without a phase change point can be obtained. This results in Q. =360
A phase modulated wave with a phase change of an odd multiple of o/2n is expressed as (n-
1) Multiplying by 1, the phase difference between adjacent time slots becomes 180o. The timing signal can be extracted by synchronously detecting this signal. FIG. 1 shows a method of extracting a timing signal by performing delayed detection and then synchronous detection. FIG. 2 shows waveforms at various parts in this example.

This embodiment is a timing signal extraction circuit that extracts a timing signal from a two-phase differential phase modulation wave (received carrier) having a phase change (90o, 270o) of an odd number multiple of 900 (1, 3, . . . times). The receiving carrier received from the input terminal of 510 and having a phase change as shown in Fig. 2a, Fig. 2b
is delayed by (1/4) cycle of the received carrier frequency in an analog delay circuit 530 as shown in FIG. 2c.

A detection circuit 540 detects the received carrier using this signal and creates a sub-received carrier shown in FIG. 2d.

The exclusive OR circuit 550 performs an exclusive OR with this signal and the sub demodulation carrier (twice the frequency of the demodulation carrier) (e) in FIG. 2 to produce a signal as shown in FIG.

The fundamental wave extraction circuit 560 extracts the fundamental wave of the signal g in FIG. 2 from this signal.

Generally, 360o/2n (a positive number where n=3...) odd number times (
When extracting a timing signal from a received carrier whose phase changes in a 2n-1 phase of 3600 or less by a factor of 1, 3, 5, etc., the discrimination circuit shown in FIG. between the fundamental wave extraction circuit.

As explained above, by detecting the received carrier every other time slot and creating a timing signal using this signal, timing information can be obtained for any phase information, and moreover, it is possible to obtain timing information for any phase information. Therefore, the position where phase information is detected does not change.

That is, the characteristics of the detection circuit can always be kept in the best condition, making it possible to perform good data transmission.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram of each part of FIG. 1, and FIG. 3 is a block diagram showing a discrimination circuit. FIGS. 5 and 7 are circuit diagrams and time charts for extracting timing from 8-phase modulated waves. FIGS. In the figure, 510 and 52 are input terminals, 540 is a detection circuit,
530 is a delay circuit, 550 is an exclusive OR circuit, 570 is an output terminal, 56 is a fundamental wave extraction circuit, 580 is a discrimination circuit, 581, 583... are delay circuits, 582, 584...
is an exclusive OR circuit. Blind drawing No. 3, 24 brothers, 4 boxes, 7 5 Zutsutomu J Prisoner No. 7 box

Claims (1)

[Claims] 1 Odd multiple of 360°/2^n (n=3,4...) (1,
In a timing signal extraction circuit used in a synchronous detection circuit for a 2^n^-^1 phase differential phase modulated wave whose phase changes by 3, 5... times), means for delaying the phase modulated wave by 1/4 cycle of its frequency. and means for delay-detecting the phase modulated wave using the delayed signal; means for synchronously detecting the delayed detection output with a demodulation carrier having twice the frequency of the phase modulation wave; (n-2) stages of signal generating circuits having means for giving a product of the delayed signal and the synchronous detection output are connected in cascade, and the delay of each delay means of each signal generating circuit is 1/8 cycle, 1/16 cycle of phase modulated wave...1/
A timing signal extraction circuit comprising a basic pulse generating means configured to have 2^n cycles, and a means for generating a timing signal from the output of the pulse generating means.