Fast-matched filters in time domain for global positioning system receivers

A fast-matched filter algorithm in time domain is presented to correlate signals for optimal detection of signals in noise, to extract ranging measurements, for synchronisation, and so on. The matched filters are discussed in the context of global positioning system receivers, but the algorithms presented here can be directly used for other direct sequence spread spectrum receivers as no constraining assumptions are made in the derivations. The method proposed here outperforms the conventional time-domain method several times in arithmetic complexity. It is also competitive with transform-domain techniques based on fast Fourier transform (FFT). Unlike FFT-based methods, however, this approach is accurate and does not use rounding or scaling operations