Fast Fourier Transform (FFT) based Phase Lock Loops (PLLs) are provided
for use in navigational signal receivers. In an embodiment, a navigation
receiver correlates a received navigational signal with a locally
generated signal into correlation samples, e.g., one-millisecond
correlation samples. The navigation receiver includes a FFT based PLL
that corrects phase shifts in the correlation samples due to the Doppler
frequency by considering both the Doppler frequency and its rate of
change, which are obtained from a FFT computation with interpolation. The
phase corrected correlation samples are then integrated over a length of
a navigation data bit, e.g., 20 milliseconds, to determine the sign of
the data bit of the received signal. In another embodiment, a soft
decision feedback technique involving integration extending over the
present data bit and several prior data bits is used to determine the
sign of a present data bit of the received signal.