A Two-Level Coarse Code Acquisition Scheme for Spread Spectrum Radio

A scheme for coarse acquisition of spread spectrum signals is described. It is characterized by a two-level acquisition process employing a passive correlator in tandem with a bank of active correlators. A threshold exceedance of the passive correlator initiates an interval of active correlation if any of the active correlators is idle. The scheme combines the rapid search capability of passive correlation with the decision reliability of (long) active correlation. An analytical model based on queuing and detection theory results is developed, and optimization of the scheme is treated. Performance in the presence of background noise with noise jamming and/or CW jamming is analyzed. Theoretical performance curves and a discussion of results are presented for each type of jamming.