Patent ID: 6125135
Filing Date: 2000-09-26
Classification: G01S,H04B

Abstract:
A global positioning satellite (GPS) demodulator configured to receive a GPS signal which includes modulated C/A code, L1 P-code, L2 P-code and encrypting W-code signals, the demodulator comprising:an L1 P-code generator configured to generate first and second L1 P-code signals that are local replica signals of the L1 P-code of the GPS signal;a first demodulator configured to demodulate the GPS signal based on, in part, the first and second L1 P-code signals, to thereby generate first and second demodulated L1 P-code signals;a first pair of integrate-and-dump (I&D) filters configured to generate a first integrated L1 P-code signal by integrating the first demodulated L1 P-code signal and configured to generate a second integrated L1 P-code signal by integrating the second demodulated L1 P-code signal during a predetermined integration period;a first thresholding module configured to generate a first switch control signal by comparing the first integrated L1 P-code signal to a first predetermined threshold value to determine whether the encrypting W-code changed polarity during the predetermined integration period; anda first switch configured to output a first adjusting signal based on a signal derived from the first and second integrated L1 P-code signals and based on the first switch control signal, wherein the L1 P-code generator is further configured to be adjusted based on a signal derived from the first adjusting signal, to thereby accurately generate the first L1 P-code signal which tracks the L1 P-code of the GPS signal.