Sweep aided Costas loop acquisition of a spread spectrum signal

When a Costas loop must acquire a DSPN spread spectrum signal over a large frequency uncertainty a sweep voltage aid may be introduced into the loop to drive the VCO over the range of uncertainty. This paper treats the problems of acquiring synchronism to the PN stream, sensing the proximity of the target frequency, and freezing the sweep voltage so that the loop is not stressed as it locks onto the received signal. The questions of and false alarm and false dismissal in sensing the proximity of the target are treated theoretically and by computer simulation. The simulation results illustrate the acquisition and lock process, and give statistical performance data.