Carrier loop architectures for tracking weak GPS signals.pdf

Carrier loop architectures for tracking weak GPS signals.pdf, The performance of various carrier recovery loop architectures (phase lock loop (PLL), Doppler-aided PLL, frequency lock loop (FLL), and Doppler-aided FLL) in tracking weak GPS signals are analyzed and experimentally validated. The effects of phase or frequency detector design, oscillator quality, coherent averaging time, and external Doppler aiding information on delaying loss of lock are quantified. It is shown that for PLLs the metric of total phase jitter is a rel iable metric for assessing low C=N performance of the tracking loop provided the loop bandwidth is not too small (»> 5 Hz). For loop bandwidths that are not too small, total phase jitter accurately predicts carrier-to-noise ratio (C=N) at which loss of lock occurs. iable metric for assessing low C=N performance of the tracking loop provided the loop bandwidth is not too small (»> 5 Hz). For loop bandwidths that are not too small, total phase jitter accurately predicts carrier-to-noise ratio (C=N) at which loss of lock occurs.