INITIAL SYNCHRONIZATION ACQUISITION CIRCUIT AND METHOD FOR REDUCING DOPPLER FREQUENCY EFFECT IN SPREAD SPECTRUM COMMUNICATIONS SYSTEM

摘要

PURPOSE: A circuit for obtaining initial synchronization of a spread communication system reducing a doppler frequency influence is provided to equally divide integration time into N sections, and to integrate signals received in each section, thereby reducing the doppler frequency influence without decreasing receiving energy. CONSTITUTION: The first to the N in-phase integrators(41_I1-41_IN) integrate signals received in the first to the N sections, and create integrated values. A reverser(42) reverses the received signals. The first to the N orthogonal phase integrators(41_Q1-41_QN) integrate the reversed signals, and create integrated values. The first adder(43a) adds up the integrated values of the in-phase integrators(41_I1-41_IN). The second adder(43b) adds up the integrated values of the orthogonal phase integrators(41_Q1-41_QN). A receiving voltage detector(44) squares the values of the first and the second adders(43a,43b) to sum up the squared values, and creates entire sectional receiving voltages by extracting a square root. The first to the N section voltage detectors(45_1-45_N) square integrated values of the first to the N sections to sum up the squared values, and create each sectional receiving voltage by extracting a square root. The third adder(46) sums up the receiving voltages. The first determiner(47a) determines that synchronization is obtained, if the receiving voltages are bigger than the first threshold value. The second determiner(47b) determines that the synchronization is obtained, if values of the third adder(46) are bigger than the second threshold value.