uld be obvious by now that once the system operating characteris- tic is determined in (3.24), the specification of acquisition performance in FH Acquisition Techniques terms of such measures as mean and variance of the acquisition time or prob- ability of acquisition follows directly from the results given in Chapter 1 for serial search PN acquisition. For example, the mean acquisition time T ACQ of the serial search FFH/MFSK system of Figure 3.5 is given by (1.34) of Chapter 1 with PD and PFA related as in (3.24) using MS+N, un, and ON 2 of (3.16)-(3.20). This parallelism between serial search PN and FH acquisi- tion systems follows from the fact that the basic Markov behavior of the search stepping procedure is the same in both cases. Further parallels between serial search PN and FH acquisition systems along the lines of sequential-type detectors, multiple dwell time detectors, optimum search procedures, etc., can also be drawn, with the details omitted here for the sake of brevity. 3.1.2 Serial Search Techniques with Passive Correlation Analogous to the matched filter techniques discussed in Chapter 1 for pseudonoise acquisition in DS/SS receivers, the rapid search capability pro- vided by a serial search scheme with passive correlation can also be realized in FH receivers. For the simplest case of rapid acquisition of an FH sequence in the absence of any information modulation, Figure 3.11 illustrates the appropriate structure. A sequence of M consecutive frequencies f1, f2. fm within the overall hop sequence is chosen as the sync pattern to which the receiver attempts to match itself. To accomplish this, the received FH sig- nal is simultaneously mixed with these M frequencies (shifted to IF) and the result of each mixture is passed through a non-coherent demodulator (band- pass filter and square-law envelope detector). The demodulator outputs are appropriately delayed SO that the sum of these outputs corresponding to the energy in M successive hop interval correlations can be formed and tested against a t