GNSS Receiver Clock and Carrier Tracking Decoupling
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Solution Overview
Problem
GNSS receivers face challenges with weak signal strength and clock errors due to using less accurate crystal clocks compared to atomic clocks, and carrier frequency distortions like line-of-sight Doppler shift, which affect accurate signal reproduction.
Innovation Solution
A dual-stage error correction scheme is implemented in a GNSS receiver, where each channel processes satellite signals to estimate clock and carrier tracking errors separately, allowing for faster correction of clock errors without adversely impacting carrier tracking, using multiple channels for improved signal synchronization and navigation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single stage of demodulation is used to correct both clock error and carrier tracking error, then device complexity is reduced, but the two signals drift in opposite directions due to multiple counting of corrections
Solution Approach 1:
The patent divides the error correction process into two separate stages: a first stage that corrects clock error using multiple channels, and a second stage that corrects carrier tracking error for each individual channel. This segmentation prevents the multiple counting problem by ensuring that clock corrections are applied once at the system level, while carrier corrections are applied separately at the channel level without re-applying the clock correction.
2Measurement precision
If clock error is corrected more frequently than carrier signal, then clock accuracy is improved, but the two signals drift in opposite directions
Solution Approach 1:
The patent implements separate correction loops with independent update rates: the clock correction loop operates at a higher rate using aggregated data from multiple channels, while the carrier tracking loop operates at a lower rate using individual channel data. This segmentation allows each loop to optimize its update frequency independently without causing signal drift.
Solution Approach 2:
The patent introduces an intermediary processing stage that aggregates carrier phase measurements from multiple channels to estimate common clock error. This intermediary step allows clock correction to be derived at a higher rate without directly impacting the carrier tracking process, as the clock correction is computed separately from the individual channel carrier measurements.
3Measurement precision
If multiple channels are used to estimate clock error, then clock error correction accuracy is improved, but device complexity increases
Solution Approach 1:
The patent makes the multiple channels serve a dual purpose: they are used both for individual carrier tracking and for aggregating clock error estimates. By processing carrier phase measurements from multiple channels through a common clock correction stage, the system extracts maximum information from each channel, improving clock accuracy without requiring separate dedicated clock correction hardware for each channel.
Data Source
AI summary
A system for navigating a mobile object receives satellite navigation signals from a plurality of satellites. Using one or more of the satellite navigation signals from the plurality of satellites, for each respective channel of a plurality of channels, the system generates an estimate of clock error of a clock of the mobile object using a first error correction stage and generates an estimate of a respective carrier tracking error for the respective channel using a second error correction stage that is distinct from the first error correction stage. In accordance with the estimate of the clock error and the estimate of the respective carrier tracking error for each of the plurality of channels, the system computes position and velocity estimates for the mobile object. The system performs a navigation function for the mobile object in accordance with the computed position and velocity estimates for the mobile object.