Demodulators – Phase shift keying or quadrature amplitude demodulator – Input signal combined with local oscillator or carrier...
Patent
1990-04-19
1991-11-12
Grimm, Siegfried H.
Demodulators
Phase shift keying or quadrature amplitude demodulator
Input signal combined with local oscillator or carrier...
375 81, 375 83, 375 97, 375120, 331 12, H04L 2722, H03L 7093
Patent
active
050651072
ABSTRACT:
A receiver for tracking a carrier suppressed phase-shifted input signal comprises a phase-locked loop circuit for receiving the input signal and having a variable frequency oscillator responsive to a control signal for oscillating at a frequency corresponding to an intermediate frequency and a frequency difference detector for producing an output signal indicative of the frequency difference between the frequency of the input signal and the intermediate frequency, a feedback loop network having a narrow-band path and a wide-band path and being responsive to the detector output signal for producing the control signal and applying the control signal to the oscillator through one of the paths whereby to change the intermediate frequency of the oscillator in response to the control signal, a quality detector responsive to the detector output signal for producing a signal corresponding to the bit error rate of the input signal; and selection means responsive to the bit error rate signal for causing the control signal to pass through the narrow-band path when the bit error rate signal is below a predetermined threshold and through the wide-band path when the bit error rate signal exceeds the predetermined threshold.
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patent: 4642573 (1987-02-01), Noda et al.
Harron Gerald
Kumar Surinder
Grimm Siegfried H.
University of Saskatchewan
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