A GPS receiver includes baseband resources for simultaneous determination
of carrier frequency shift and code chip offset. Reduction in the power
consumption of a receiver is achieved by managing the sampling rate of an
analog-to-digital converter, the intermediate frequency of the RF front
end, and the front end bandwidth so these are appropriate to the current
function of the receiver. In a GPS receiver during signal tracking, the
IF, front end bandwidth, and ADC sampling rate are set as high as
possible; during signal acquisition, the IF and front end bandwidth are
set to relatively low values, and the ADC sample rate is set to a high
value; and during ephemeris download, the IF, front end bandwidth, and
the ADC sample rate are set to relatively low values. When a low battery
condition is detected, the IF, front end bandwidth, and the ADC sample
rate are set to relatively low values regardless of whether the GPS
receiver is in the signal acquisition mode, signal tracking mode, or
ephemeris download mode.