Coherent demodulator for .pi./4 shifted QPSK signal

Details Coherent demodulator for .pi./4 shifted QPSK signal Coherent demodulator for .pi./4 shifted QPSK signal

1991-01-22

1993-01-12

Kuntz, Curtis

Pulse or digital communications

Repeaters

Testing

375 54, 375 81, 375 83, 329304, 329306, H03D 322, H04L 2722

Patent

active

051795787

ABSTRACT:
A demodulator for coherent demodulation of a .pi./4 shifted QPSK signal includes a -.pi./4 phase-shift circuit in a conventional QPSK signal decision/feedback type Costas loop to alternately rotate the phase of an inputted .pi./4 shifted QPSK signal by 0 and -.pi./4 for each symbol period interval from a timing controller, thus eliminating the .pi./4 shift component of the .pi./4 shifted QPSK signal. Thus, coherent detection demodulation for the .pi./4 shifted QPSK signal having stable points at intervals of .pi./2 phase angles is enabled.

REFERENCES:
patent: 4054838 (1977-10-01), Tretter
patent: 4085378 (1978-04-01), Ryan et al.
patent: 4255713 (1981-03-01), Yoshida
patent: 4344178 (1982-08-01), Waters
patent: 4520493 (1985-05-01), Heard et al.

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