reasing K (the number of dwell penalty time units) requires an attendant decrease in PFA FA to achieve the same level of performance. In this regard, the value of K is critical in determining the value of PFA which yields near optimum performance. Before leaving this section we point out that the heuristic approach used to verify the mean time to acquisition and acquisition variance results derived from the flow graph diagram can also be applied here to obtain the acquisition probability behavior. The details are left as an exercise for the reader. As a head start, one can easily show that for PEA = 0, convo- lution of (1.8) with (1.19) gives the probability density function for (1.99) As a final note, we point out the relation of the single dwell system with stepped search discussed here to an equivalent acquisition system using a continuous sweep. In the latter case, the local PN code generator is clocked at a frequency f + of which differs from the clock frequency fc = 1/T of the incoming PN code by a small amount of << fc. As such, the epoch ference between the incoming and local PN codes vanishes at instants of time which are plof apart where p is again the period of the PN code in chips. When the input and local codes are actively correlated, the result is a periodic train of "impulses" (traingular pulses of width 2/8fc) which occur at the instants of vanishing epoch difference. These impulses are detected Pseudonoise Code Acquisition in Direct-Sequence Receivers by means of a non-coherent detection circuit consisting, as we have already seen, of a pre-detection band-pass filter, a quadratic detector, a post-detec- tion low-pass filter, and a threshold device. The first detected "impulse" declares a "hit," sets the local clock frequency to fc, and activates the track- ing loop. To extend the performance results obtained for the discrete stepping search to the continuous sweep procedure, one must merely equivalence qTd in the former with the time pldf to equivalently search one code period in the latter. Fur