US Patent 7936642 High sensitivity GPS-assisted time source

A method for determining portions of a GPS satellite signal may use non-coherent integration to determine a repeated pattern such as a preamble. Once the repeated pattern is determined, portions of the GPS satellite signal that may be determined with partial correlation sums. Sensitivity to satellite signals may be increased by computing more partial correlation sums on portions of the GPS satellite signal. In one embodiment, time of day information may be determined from the GPS satellite signal with partial correlation sums.