| 摘要 |
Methods for synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, which consists of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal. An idealized correlation function AI(t), formed from the product of a digital reference signal with a time-shifted reference signal, and a measured correlation signal AM(t), formed from the product of a received signal and a time-shifted reference signal, are computed. Peak amplitudes AM(pM) and AI(pI) are found for the respective measurable and idealized punctual code phase shifts pM and pI. In a first embodiment of the invention, the correlation measurements formed on the early side (or on the late side) of the peak for the correlation function A(t) are combined to form an estimate of the time delay associated with a multipath signal. In a second embodiment, correlation measurements formed on both the early and late sides of the peak are combined to form an estimate of the multipath time delay. In a third embodiment, a gradient difference is formed from two sets of correlation measurements to estimate the multipath time delay. In a fourth embodiment, correlation functions formed from in-phase and quadrature signals are used to estimate the multipath time delay. This fourth embodiment allows code phase multipath time delay to be measured in the absence of receiver carrier phase lock. All four embodiments may be used in a fixed amplitude variable time (FAVT) mode and in a fixed time variable amplitude (FTVA) mode.
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