Demodulator

Details Demodulator Demodulator

1994-09-14

1995-08-08

Mis, David

Demodulators

Phase shift keying or quadrature amplitude demodulator

Input signal combined with local oscillator or carrier...

329309, 375332, 375362, 375376, H03D 300

Patent

active

054402670

ABSTRACT:
In a demodulator, a delay detection means receives a .pi./4-shift QPSK signal and performs delay detection of a signal at an interval of symbols. An averaging circuit respectively averages two channel quadrature signal components of a signal. A preamble detection means detects a preamble having a specific pattern in which a phase shift of .pi./4 of the phase of a received symbol from the immediately preceding symbol and a phase shift of -3.pi./4 of a phase of a next symbol from the immediately preceding symbol are alternately repeated on a phase plane of the two channel quadrature signal components. A phase angle calculating means calculates the phase angle of an output signal from the averaging circuit. A frequency offset estimating circuit calculates a carrier frequency offset. A voltage-controlled oscillator has an output oscillation frequency variably controlled by an output signal from the frequency offset estimating circuit. A frequency converter performs frequency conversion of the output oscillation frequency of the voltage-controlled oscillator and the input .pi./4-shift QPSK signal. A reproduction circuit reproduces a carrier and a clock from an output .pi./4-shift QPSK signal from the frequency converter, and obtains demodulated data by coherent detection.

REFERENCES:
patent: 4888793 (1989-12-01), Chanroo et al.
R. Yamamoto et al., "A Clock Recovery Circuit Using Geometric Character of Preamble", The 1993 IEICE Spring Conference, B-316.
A. Blanchard, "Phase-Locked Loops", A Wiley-Interscience publication, John Wiley & Sons, 1976, pp. 280-289.

Affiliated with

Also associated with

Rating

Demodulator does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Demodulator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Demodulator will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-974267