sition process in terms of the underlying tradeoff between false alarm and detection probabilities. As before, we start out with the same basic assumptions, namely, that no a priori knowledge of the currect cell's location within the total uncertainty region is available and the cell-by-cell search of the entire uncertainty region is repeated until the correct cell is detected. Although not explicitly stated previously, each cell is assumed to be tested only once during each search of the uncertainty region and the order of the cells in the search is inconsequential. To make matters simple, we assume at first that during each examination of a cell, the detector is characterized by a constant (time-invariant) detec- tion probability PD as before, but now, however, a zero false alarm proba- bility. Then, if k (integer) denotes the particular search of the uncertainty region during which the correct cell is first detected, then k has the geometric probability density function (pdf) p(k) = k = 1,2,3, (1.8) Note that since, by assumption, PFA = 0, then the detection probability for each complete search of the entire uncertainty region is equal to the detec- tion probability for the correct cell, namely, PD. Furthermore, k - 1 repre- sents the number of unsuccessful searches of the uncertainty region, each having passed through q cells. Thus, Nq(k-1) (1.9) is an integer random variable which represents the number of cells searched without success of detection prior to the k-th search during which the correct cell will be detected. Since each of these N'u cell examinations occupied a single dwell time Td, (1.10) represents the time expired in passing through this unsuccessful series of searches. The mean and variance of T'u are readily computed as follows: (1.11) Since, by definition, p(k) is a probability density function, (1.12) Furthermore, differentiating both sides of (1.12) with respect to PD and sim- plifying gives (1.13) Pseudonoise Code Acquisition in Direct-Sequence Receivers Thus, combining (1.12) and (1.13) 