Importance

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Abstract

A method and apparatus for generating a frequency offset estimate and a timing offset estimate from a base band signal. In an important application of the invention, a modulated carrier signal is transmitted over a transmission channel and then received and demodulated to generate the base band signal. The modulated carrier signal comprises data having a transmitted symbol frequency and phase, and a carrier signal modulated by the data. The invention simultaneously generates from the base band signal a frequency offset estimate representing the difference between the transmitted and received carrier signal frequency, and a timing offset estimate representing the difference between the transmitted symbol phase and the recovered symbol phase of the base band signal. In preferred embodiments, the base band signal is a digital signal sampled at a rate which exceeds the Nyquist rate. Typically, a sampling rate of more than two samples per symbol is adequate to meet this condition. A pair of nonlinear operations is performed on this digital base band signal, and the resulting two nonlinear signals are processed to generate the frequency offset and timing offset estimates.

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First Claim