Citation
Abstract
In this article, we analyze mathematical models of digital loops used to track the phase and timing of communications and navigation signals. The limits on the accuracy of phase and timing estimates play a critical role in the accuracy achievable in telemetry ranging applications. We describe in detail a practical algorithm to compute the loop parameters for discrete update (DU) and continuous update (CU) loop formulations, and we show that a simple power-series approximation to the DU model is valid over a large range of time-bandwidth product (B T). Several numerical examples compare the estimation error L variance of the DU and CU models to each other and to Cramér-Rao lower bounds. Finally, the results are applied to the problem of ranging, by evaluating the performance of a phaselocked loop designed to track a typical ambiguity-resolving pseudonoise (PN) code received and demodulated at the spacecraft on the uplink part of the two-way ranging link, and a data transition tracking loop (DTTL) on the downlink part.
Details
- Volume
- 42-202
- Published
- August 15, 2015
- Pages
- 1–27
- File Size
- 957.7 KB