Demodulators – Phase shift keying or quadrature amplitude demodulator – Input signal combined with local oscillator or carrier...
Patent
1994-08-04
1996-01-16
Callahan, Timothy P.
Demodulators
Phase shift keying or quadrature amplitude demodulator
Input signal combined with local oscillator or carrier...
329310, 375328, 375330, H04L 2722
Patent
active
054849870
ABSTRACT:
Within the differential detection demodulator, the received signal is first quantized by a limiter amplifier and then subjected to frequency conversion by a frequency converter including: an exclusive OR element; a running average generator consisting of a shift register and an adder; and a comparator. In response to the output of the frequency converter, the phase comparator outputs a relative phase signal representing the phase shift of the received signal after frequency conversion relative to the phase signal representing the phase shift of the received signal after frequency conversion relative to the phase reference signal. The phase comparator includes: an exclusive OR element; an absolute phase shift measurement means consisting of an adder and D flip-flop arrays and; and a D flip-flop serving as a phase shift polarity decision means. Alternatively, the phase detection circuit for generating the relative phase signal may include: a half-period detection means consisting of a delay element and an exclusive OR element; a phase reference signal generation means consisting of a modulo 2N counter; and a phase shift measurement means consisting of a phase inversion corrector and a D flip-flop array. The delay element delays the relative phase signal by one symbol period and the subtractor outputs the phase difference signal representing the phase transition over each symbol period of the received signal. The decision circuit obtains the demodulated data from the phase difference signal.
REFERENCES:
patent: 5055801 (1991-10-01), Koga et al.
patent: 5313170 (1994-05-01), Kojima
Callahan Timothy P.
Lam T.
Mitsubishi Denki & Kabushiki Kaisha
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