N-phase modulated signal demodulation system with carrier reprod

Details N-phase modulated signal demodulation system with carrier reprod N-phase modulated signal demodulation system with carrier reprod

1995-09-12

1997-03-25

Grimm, Siegfried H.

Demodulators

Phase shift keying or quadrature amplitude demodulator

Input signal combined with local oscillator or carrier...

329309, 329310, 375326, 375327, 375328, 375332, H04L 27227

Patent

active

056148615

ABSTRACT:
A phase modulated signal demodulation system which is not affected by noise and distortion of an input signal. The system includes a carrier reproduction PLL circuit for generating a reproduction reference clock having a frequency which is N times of a carrier frequency which is synchronized with an N-phase phase modulated input signal, and a clock generation circuit for dividing the reproduction reference clock by 1/N and for generating N clocks, each of which has a different phase offset by 360.degree./N. The system further includes a phase detector which detects a phase of the N-phase phase modulated signal by using the N clocks together with the input N-phase phase modulated signal; and an operating circuit which detects a data edge of the input signal and the reproduction reference clock. The system further includes a data clock reproduction PLL circuit for generating a clock synchronized with a data rate using an output from the operating circuit, and a second clock generation circuit which generates a plurality of clocks for majority judgments using an output of the data clock reproduction PLL circuit. The system further includes a data protection circuit for protecting data generated by the phase detector, and a data generating circuit which outputs a corresponding digital data according to phase information outputted from the phase detector.

REFERENCES:
patent: 4308503 (1981-12-01), Scott
patent: 4466109 (1984-08-01), Sari
patent: 5440268 (1995-08-01), Taga et al.
"Manufacturing QPSK Digital Modulator-Demodulator," Electronics Life, NHK Publishing Society, 1992, pp. 81-91.

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