Patent ID: 7529328

Claim:
A Doppler frequency estimator, comprising: a band-pass filter unit configured to perform a band-pass filtering operation on demodulated signals with respect to a modulo-2 search band to provide filtered signal pairs; a non-coherent accumulator configured to execute a non-coherent accumulation on each of the filtered signal pairs to provide non-coherent accumulated signal pairs; a comparator configured to compare the non-coherent accumulated signal pairs with each other to provide a larger one of the non-coherent accumulated signal pairs as a detection signal; and a search control unit configured to iteratively generate control signals for a predetermined number of search periods to provide the control signals to the band-pass filter unit, and configured to determine that a detection signal detected at a final search period is a Doppler frequency, wherein the control signals narrow a search band by setting an initial modulo-2 search band during an initial search period and setting a modulo-2 search band of a next search period, wherein the modulo-2 search band of the next search period is the initial modulo-2 search band divided in accordance with the detection signal such that a bandwidth of the modulo-2 search band of the next search period is less than a bandwidth of the initial modulo-2 search band.