Patent ID: 7991043

Claim:
A demodulator for de-spreading a digitally-modulated signal including a plurality of symbols, each symbol having a symbol period and spread among a plurality of chips, the digitally-modulated signal including a preamble of pre-determined symbols, the demodulator comprising: a correlator for performing correlations, the correlator including: a tapped delay line including a plurality of registers, each register for holding a chip of a symbol of the digitally-modulated signal as a function of time, taps operatively coupled to registers for performing a tap weight operation on each chip to rotate a phase of each chip to correct a frequency offset from a nominal carrier frequency, and a magnitude calculator for calculating a magnitude of each correlation; a first counter; a second counter; a correlator control module for changing the taps to a different set of tap weight values a plurality of times during each symbol period, and, for each set of tap weight values, causing the correlator to correlate the digitally-modulated signal to a first symbol and to a second symbol, thereby performing a sequence of correlations during each symbol period; and a detection and synchronization module, coupled to the first counter and the second counter, for determining a location, within a first symbol period, of correlations to the first pre-determined symbol and for determining a location, within a second symbol period, of correlations to the second pre-determined symbol, the detection and synchronization module including: a maximum magnitude module, coupled to the correlator, for selecting a peak magnitude from each sequence of correlations for a corresponding symbol period, and a detection module for determining presence of a preamble in the digitally-modulated signal based upon peak magnitudes, location within a symbol period of each peak magnitude, and the set of tap weight values in use at each peak magnitude.