A closed-loop coherent PN acquisition system with a pre-loop estimator

We propose a closed-loop system with a pre-loop code phase estimator (PLE) for acquisition of the pseudonoise (PN) signal in direct-sequence spread-sp ectrum systems. It consists of two major parts: a PLE and a closed-loop acq uisition subsystem. The system uses an auxiliary signal, as opposed to the PN signal itself, to correlate with the incoming signal, The PLE uses the c orrelation result to obtain an estimate of the incoming code phase. Then, s tarting with this initial estimate, the closed-loop subsystem will acquire the code phase of the incoming PN signal. With coherent carrier demodulatio n, mean and variance of the acquisition time of the proposed scheme are obt ained and compared to those of the conventional serial-search acquisition r eceiver and the closed-loop system without the pre-loop estimator. Results show that, with proper choices of parameters, the proposed system acquires the PN phase significantly faster than the other two systems.