Demodulators – Phase shift keying or quadrature amplitude demodulator – Input signal combined with local oscillator or carrier...
Patent
1991-05-17
1992-05-26
Grimm, Siegfried H.
Demodulators
Phase shift keying or quadrature amplitude demodulator
Input signal combined with local oscillator or carrier...
329309, 329310, 375 81, 375 83, H04L 2722
Patent
active
051171953
ABSTRACT:
A data referenced demodulator is provided for recovering differentially encoded multiphase modulated digital data such as QPSK modulated audio data. An analog carrier containing the differentially encoded QPSK data is converted to a digital waveform at an intermediate frequency that is a multiple of the QPSK bit frequency. The digital waveform is delayed in a shift register that samples the waveform at a clock rate which is a multiple of the intermediate frequency. Different stages of the shift register output the digital waveform one bit time earlier plus 45.degree. and one bit time earlier minus 45.degree.. These outputs of the shift register are multipled with the digital waveform using exclusive OR gates to provide differential QPSK detection. The shift register sampling clock is phase locked to a system master clock, which in turn is locked to the received data. In an illustrated embodiment, the sampling clock is 24 times the intermediate frequency, providing 15.degree. phase resolution.
REFERENCES:
patent: 3938052 (1976-02-01), Glasson et al.
patent: 3980824 (1976-09-01), Lamb et al.
patent: 4714892 (1987-12-01), Ishizuka
patent: 4821097 (1989-04-01), Robbins
C. Robbins, "Digital Audio for Cable Television," 1986 NCTA Technical Papers, Dallas, Texas, Mar. 15-18, 1986, pp. 21-24.
General Instrument Corporation
Grimm Siegfried H.
Lipsitz Barry R.
LandOfFree
Data referenced demodulation of multiphase modulated data does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Data referenced demodulation of multiphase modulated data, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data referenced demodulation of multiphase modulated data will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-422539