Acquisition of GNSS Signals with Secondary Code Figure 17. Timing diagram of the implementation of the pre-FFT secondary code removal in a parallel way (Figure 4 with only two accumulators) with NS = 4. The 2 processing time to compute K times the full correlation is K × [(2NPNS + NZ) NS/2] + NFFT + L + NFFT + L + NP = NP(K N S + 5) + NZ(KNS/2 + 2) + 2L. Figure 18. Timing diagram of the implementation of the post-FFT secondary code removal using a memory (Figure 5) with NS = 4. The processing time to compute K times the full correlation is NFFT + L + NFFT + L + K[NFFT(NS - 1) - NP(NS - 1) + NPNS ( NS - 1)] + NPNS = NP [K ( N S2 - 1) + NS + 4] + NZ [ K (NS - 1) + 2] + 2L. Figure 19. Timing diagram of the implementation of the post-FFT secondary code removal without memory in a sequential way (Figure 6) with NS = 4. The pro2 2 2 cessing time to compute K times the full correlation is NFFT + L + NFFT + L + KNFFT N S - (NP + NZ) = NP(2K N S + 3) + NZ(K N S + 1) + 2L. 60 IEEE A&E SYSTEMS MAGAZINE AUGUST 2017