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Method and apparatus for rapidly estimating the doppler-error and other receiver frequency errors of global positioning system satellite signals weakened by obstructions in the signal path
Method and apparatus for rapidly estimating the doppler-error and other receiver frequency errors of global positioning system satellite signals weakened by obstructions in the signal path
Frequency-offset components are extracted from a set of digitized samples of signals transmitted by a satellite. The samples are squared to produce squared samples and decimated. The squared samples are auto-correlated to produce an auto-correlate, and the auto-correlate is truncated. The truncated auto-correlate is transformed into the frequency domain to obtain double-frequency offset components. The scaled offset frequencies are used to compensate for Döppler-shift and receiver frequency errors and for Döppler induced time errors in digitized samples used to estimate pseudorange information.
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