Selective type quadrature demodulator

Details Selective type quadrature demodulator Selective type quadrature demodulator

1995-05-09

1996-06-18

Grimm, Siegfried H.

Demodulators

Phase shift keying or quadrature amplitude demodulator

Input signal combined with local oscillator or carrier...

329309, 375327, 375376, H04L 2738

Patent

active

055281958

ABSTRACT:
A quadrature demodulator for demodulating an input signal which includes respective data signals modulating in-phase and quadrature carriers. The demodulator includes a voltage controlled oscillator responsive to a control signal for generating an oscillatory signal. A demodulator, coupled to receive the oscillatory signal from the voltage controlled oscillator and the input signal, provides the in-phase and quadrature components of the input signal. Phase comparison circuitry, responsive to the in-phase and quadrature components of the input signal generates a phase error signal. The phase error signal represents the difference, in phase and magnitude, between a vector defined by the in-phase and quadrature components of the input signal and reference vectors. Filter circuitry, responsive to the phase error signal, generates a control signal for the voltage controlled oscillator. Phase error correction circuitry selectively applies the error signal to the filter circuitry when the magnitude of a vector defined by the in-phase and quadrature components of the input signal exceeds a first threshold. Another embodiment provides the phase error signal to the filter circuitry when the magnitude of a vector defined by the in-phase and quadrature components of the input signal either exceeds a first threshold or is less than a second threshold.

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F. M. Gardner, "Self-noise in Synchronizers", IEE Transactions on Communications, vol. 28, pp. 1159-1163 (Aug. 1980).

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