Patent ID: 8254512
Filing Date: 2012-08-28
Classification: G01S

Abstract:
1. A method of using a long coherent integration period to receive a positioning signal transmitted from one of a plurality of transmitters at a predetermined carrier frequency, the positioning signal including a reference signal that uniquely identifies the transmitter that sent the positioning signal, comprising: a) observing electromagnetic energy at about said carrier frequency, and providing data responsive to said observed electromagnetic energy; b) hypothesizing one of said transmitters, thereby hypothesizing one of said plurality of unique reference signals; c) hypothesizing a frequency drift, wherein the frequency drift changes according to a lapse in time; d) processing, using a processor, said data responsive to said hypothesized frequency drift; e) defining a data block of said data; f) searching for a match between said data block and said hypothesized unique reference signal; and g) if a matched signal is found, then determining phase delay and timing information, otherwise looping through said steps b through f until a matched signal is found or until a predetermined exit criteria has been met.