acquisiton system. Since for either correlator configu- ration the outputs occur and are ultimately (after squaring and summing) threshold tested at N times the chip rate, the search rate for this acquisition method is clearly N/T 1/N-chip positions per second, (1.179) which is a factor of NTd/Tc = NM faster than that of the serial search tech- nique. This large apparent improvement in search rate, or equivalently, the time to search over the total uncertainty region, is a consequence of the fact that in the MF system, only one new fractional (1/N) chip of received signal is used for each correlation test since the prior NM - 1 received signal sam- ples are already stored in the tapped delay line or shift register. Because of this fact, however, it would appear that the noise-corrupted correlation val- Rapid Acquisition Using Matched Filter Techniques ues from test to test would be highly correlated because of the NM - 1 sam- ple overlap as contrasted to the same test values in the single dwell serial search method which are clearly independent of one another because of the disjont observations. Nevertheless, it can be shown [14] that, despite the over- lap, the underlying acquisition process is still Markov and hence the flow graph model of the unified approach discussed in Section 1.4 can be used to determine its acquisition time performance. Before proceeding to a discussion of the acquisition time performance, we first complete the description of the system by presenting a method of ver- ification of the threshold crossing event. In particular, the non-coherent cor- relator/detector structure of Figure 1.25b is followed by a coincidence SAMPLE AT 1=KT/IN NM STAGE TAPPED DELAY LINE 1-TCIN LOAD PN CODE WEIGHTING SEGMENT (Di's) SUMMATION CORRELATION Figure 1.27a. An analog correlator implementation of a matched filter. SAMPLE AT 1 SKT IN 1- BIT SHIFT REGISTER 1-TC/N COMPARE 8 SUM CORRELATION HOLDING REGISTER LOAD PN SEGMENT (2;'s) Figure 1.27b. A digital correlator implementation of a matched filter. Pseudonoise