Patent ID: 7120191

Claim:
A method for determining information about a carrier frequency of a signal transmitted by a possibly moving transmitter, the signal having a code component and a carrier component at the carrier frequency, the method comprising: a) responding to successive approximately carrier-demodulated received signal fragments of the signal, and providing a set of correlation results indicating information about a correlation of the successive approximately carrier-demodulated received signal fragments with phase-shifted replicas of the code component, wherein the successive approximately carrier-demodulated received signal fragments are formed using different possible offsets from a nominal carrier frequency, and further wherein each element of the set is provided as a phasor having a magnitude and a phase; and b) responding to the set of phasors, selecting the phasor having a magnitude distinguishing it from all the other elements of the set, and determining the phase of the selected phasor; wherein providing the set of correlation results includes performing a coherent integration of the successive approximately carrier-demodulated received signal fragments, and performing a non-coherent integration in which phasor results of the coherent integrations are combined without regard to phase; and further wherein performing the non-coherent integration involves multiplying each element of a matrix of correlation results provided using a coherent integration of a first signal fragment, by the complex conjugate of a corresponding element for an immediately preceding signal fragment.