Patent ID: 8665151

Claim:
A method of deriving an amplitude and a pseudo-Doppler phase of an L2 signal from L1 and L2 signals received in a global positioning system, each of said L1 and L2 signals including a separate carrier frequency modulated by a known P-code and unknown W-code, the method comprising the steps of: amplifying and filtering L1 and L2 signals received from an antenna, and downconverting them to complex video frequency L1 and L2 signals; converting said complex video frequency L1 and L2 signals to a digital form; demodulating the digital complex video frequency L1 and L2 signals with a locally generated P-code replica to generate demodulated complex L1 and L2 signals; shifting a pseudo-Doppler phase of said demodulated complex L1 signal by a locally generated digital phase that changes from a first initial phase linearly in accordance with a first frequency to generate a demodulated Doppler-compensated L1 signal; shifting the pseudo-Doppler phase of said demodulated complex L2 signal by a locally generated digital phase that changes from a second initial phase linearly in accordance with a second frequency to generate a demodulated Doppler-compensated L2 signal; integrating said demodulated Doppler-compensated L1 and L2 signals over a first predefined time period to generate pre-integrated L1 and L2 signals; weighting an in-phase component of said pre-integrated L1 signal with a first weighting factor to generate a weighted in-phase L1 signal; weighting an in-phase component of said pre-integrated L2 signal with a second weighting factor to generate a weighted in-phase L2 signal; adding said weighted in-phase L1 signal to said weighted in-phase L2 signal to generate a total weighted in-phase signal; comparing a magnitude of said total weighted in-phase signal with a predefined threshold to generate an overshoot indicator; inverting said pre-integrated L2 signal by a sign of said total weighted in-phase signal to generate a decrypted L2 signal; and integrating said decrypted L2 signal over a second predefined time period on condition of said overshoot indicator to produce a complex integrated L2 signal the magnitude of which is proportional to a desired output amplitude of the L2 signal, and which phase, being added to said second initial phase, is equal to a desired output pseudo-Doppler phase of the L2 signal.