Hughes Aircraft Company

Hughes Electronics Corporation

Janavikulam Anandkumar

Richard Clewer

Andrew MacDonald

A symbol timing recovery method and device which aligns the received data with a free-running symbol clock such that the aligned data sampling error is minimized. The symbol timing recovery process consists of detecting the timing phase error between the transmitters symbol clock and the receiver symbol clock, filtering the error, and then using the filtered error signal to control a block which changes the phase of the data relative to the timing reference signal. A data zero-crossing phase error detector drives a loop filter whose most significant bits form the address of the FIR coefficient ROM, which allows the FIR to interpolate data at sub-symbol resolution. The FIR coefficients are then used to synchronize the received data with the receiver clock.

Symbol timing recovery using fir data interpolators

A method and apparatus for use in estimating phase error in a phase-modulated carrier. The method and apparatus of the present invention may be embodied in a phase-error-estimator circuit which is typically incorporated into a demodulator of a digital communications receiver. In general, the phase-error-estimator circuit receives the I and Q components of a phase-modulated signal, and outputs an estimate of the phase error, if any, in the phase-modulated carrier signal associated with the received I and Q. Preferably, the phase-error-estimator circuit includes an index/polarity generator circuit coupled to a look-up table. The index/polarity generator receives I and Q and maps them onto a reduced range of phase angles represented by values X and Y. X and Y are fed to a reduced and substantially triangular look-up table which outputs the stored phase-error-estimate for the particular X and Y inputs.

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Gaithersburg, MD, United States of America

Janavikulam Anandkumar