Acquisition of spread spectrum codes in hybrid systems

An acquisition procedure for the various pseudonoise sequences used in the hybrid FH/DS (Frequency Hopping/Direct Sequence) and FH/TH (T = time) spread spectrum systems is presented. The frequency hopping code is acquired by an autoregressive spectral estimation technique, ASEAT. The direct sequence code in FH/DS is acquired by a simple quadrature processing model, and the time gating code in FH/TH is acquired by a simple threshold comparison test used in conjunction with ASEAT. Illustrative examples are given for both the hybrid systems and the simulation results are presented for moderate carrier-to-noise ratios and system processing gains. The acquisition time is of the order of the pseudonoise sequence shift register generator delays.