abilities PFA1 = .001,.01, .03, and 0.1, we obtain from (1.300) and (1.299) the corresponding values of mean dwell time Td = .912, .934, 1.016, and 1.7 ms which are independent of P/No. Finally, using the above-deter- mined functional relationship between PL and P/N together with the val- ues of Td in (1.288) gives the mean acquisition time of the system, which is illustrated versus PIN in Figure 1.64. Note that, for smaller values of PFA1, TACQ increases faster with decreasing P/N than is the case for larger PEA1 The effect is primarily due to the increased PD1 which results from increased PFA1. We hasten to add that all of the results of this section have assumed the absence of code Doppler or its derivatives. To include these effects, one Dic=-300Hz = - (SEARCH MODE) PFA1=0.03 (LOCK MODE) PFA2 = 0.5 A fc = O fc = 300Hz No P dB-Hz Figure 1.64. Mean acquisition time performance; +300 Hz frequency error (reprinted from [9]). Pseudonoise Code Acquisition in Direct-Sequence Receivers would simply apply the modifications discussed in Sections 1.2.3 and 1.2.8 to (1.288) and (1.289). For example, the relation for mean acquisition time in the presence of code Doppler analogous to (1.48a) would now be (see (1.288)) (1.303) where again Nu/q' represents the search update in the absence of Doppler, e.g., one-half of a chip, and Afcd is the code phase shift due to Doppler dur- ing the mean dwell time. As a numerical illustration of the application of (1.303), Figure 1.64 plots TACQ versus P/N for the previous example with now Afc = -300 Hz or Afc = +300 Hz and Nu/q' = 1/2. 1.8.2 Another Search/Lock Strategy Another approach [1] to providing an SLS incorporates a search mode which is modelled after the multiple dwell time acquisition procedure dis- cussed in Section 1.3. In particular, the search mode again consists of two states; however, unlike Figure 1.59, the integration (dwell) times are dif- ferent for the two states. Furthermore, a miss on state 2 does not return the SLS to state 1 but rather immediately dismisses the