A novel multi-stage estimation of signal parameters

A novel multistage estimation scheme is presented for estimating the parameters of a received carrier signal possibly phase-modulated by unknown data, and experiencing very high Doppler, Doppler rate, etc. Such a situation arises, for example, in the case of the Global Positioning System (GPS), where the signal parameters are directly related to the position, velocity, acceleration, and jerk of the GPS receiver. In the proposed multistage scheme, the first-stage estimator operates as a coarse estimator, resulting in higher root mean square estimation errors, but with a relatively small probability of the frequency estimation error exceeding one-half of the sample frequency (an event termed cycle slip). The second stage of the estimator operates on the error signal available from the first stage, refining the overall estimates, and in the process also reduces the number of cycle slips. One of the main advantages of the proposed algorithms is the reduction in threshold on received carrier power-to-noise power spectral density ratio