ces among these various forms of multiplication will be partly responsible for the classification of PN acquisition systems to be discussed shortly. Pseudonoise Code Acquisition in Direct-Sequence Receivers differences between the various schemes depend on (1) the type of detec- tor (and decision strategy) used, which, in turn, is dependent on the form of the received signal and the particular application at hand, and (2) the nature of the search algorithm which acts on the detector outputs to reach the final verdict.2 All known detectors for PN acquisition systems, in one form or another, fall into two basic categories, namely, coherent or non-coherent. By far the most common found in acquisition systems for DS/SS receivers is the non- coherent detector which, for example, might be comprised of a band-pass filter centered at the frequency of the received carrier upon which the PN signal is direct modulated, followed by a square-law envelope detector,3 an integrate-and-dump circuit which operates over a finite time interval, and a simple threshold device [1]. The reason why the non-coherent detector is most commonly found is that the despreading operation typically takes place ahead of the carrier synchronization function; thus, at the point in time at which PN acquisition is to be accomplished, the carrier phase must be assumed to be unknown. Consideration has also been given in the literature to PN acquisition sys- tems which operate under the assumption that the receiver is capable of determining good estimates of the carrier phase and frequency shifts brought about by the propagation delay and Doppler produced by the transmission channel, in which case, the carrier can be "demodulated" prior to PN despreading. In these instances, the PN acquisition system can employ a coherent detector which typically might consist of a low-pass fil- ter (possibly implemented as an integrate-and-dump circuit) followed by an optimum Bayes detector [2], [3] or instead just a simple threshold device [4], [5]. It is convenient in