Spread spectrum techniques have become very useful in modern communications. A common spread spectrum technique is to directly modulate a pseudorandom noise (PN) code onto the carrier. Systems employing this technique are called direct sequence (DS) systems. A primary concern with direct sequence systems involves PN code synchronization (acquisition) of the incoming and local signals to within at least one PN symbol followed by a fine alignment (tracking) which must be maintained throughout transmission. This paper is concerned with the PN acquisition aspect of code synchronization. Specifically, a dual threshold sequential detection receiver is analyzed and a general expression is derived which addresses the probability that the sequential detection procedure ceases after an arbitrary number of samples. This expression is needed in order to support a characteristic function approach in deriving acquisition Probability as a function of time which will be the topic of a subsequent paper.

A noncoherent delay-lock PN tracking loop is investigated. The approach used is one in which simulation and analysis are combined to generate tracking performance. Performance data are presented for PN phase jitter standard deviation and compared to theoretical results. The impact of radio frequency interference (RFI) and gain/phase imbalances on PN tracking performance is determined and performance data are given. It is suggested that self-noise terms (introduced via the correlation operation between the incoming signal and local PN code) and nonideal arm-filter characteristics (resulting in gain/phase imbalances) may be significant factors in the investigation of PN tracking performance for those cases in which PN code timing synchronization is a major concern.