| 主权项 |
1. A satellite-based positioning system (SPS) receiver, comprising:
an RF front end configured to receive a series of PRN sequences from an SPS satellite responsive to an assertion of a wakeup signal, the received series of PRN sequences having a phase modulation responsive to a navigation bit overlay; an analog-to-digital converter (ADC) configured to sample the series of received PRN sequences across a sampling window to provide original time samples responsive to an SPS clock having an SPS sampling rate; a perfect reference generator configured to generate perfect reference samples for a plurality of candidate perfect reference sampling periods within a perfect reference search window comprising a series of perfect reference PRN sequences, wherein the perfect reference PRN sequences have a conjugate phase modulation that is the complex conjugate of the phase modulation for the navigation bit overlay; a re-sampler configured to re-sample the original time samples according to a first effective sampling rate different from the SPS sampling rate to provide first re-sampled time samples; and a cross-correlator configured to coherently cross-correlate the first re-sampled time samples with the perfect reference samples for a selected one of the candidate preference reference sampling periods to provide a first cross-correlation sum; and a detection module configured to assert the wakeup signal at the start of the sampling window and to de-assert the wakeup signal at the end of the sampling window, wherein the detection module is further configured to adjust the selection of the candidate perfect reference sampling period to search the plurality of candidate perfect reference sampling periods to detect a first peak value in the first cross-correlation sum. |
