GPS Vector Tracking via Non-Coherent Integration
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Solution Overview
Problem
Traditional GPS receivers face challenges in high dynamic environments due to large Doppler frequency shifts, leading to difficulties in initial tracking, signal loss, and poor tracking precision, especially in weak signal conditions.
Innovation Solution
A joint non-coherent integral vector tracking method is employed, using Extended Kalman Filter for optimal estimation of navigation state parameters and forming a closed-loop tracking loop, which improves the carrier-to-noise ratio and tracking sensitivity by processing baseband signals from multiple channels simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wider bandwidth frequency-locked loop or phase-locked loop is used to overcome large Doppler frequency shift, then initial tracking can be achieved, but tracking precision deteriorates due to increased filter noise bandwidth
Solution Approach 1:
The patent segments the tracking process into two distinct phases: acquisition phase using wide bandwidth loops for initial tracking, and tracking phase using narrow bandwidth loops for precision. The vector tracking loop separates code tracking and carrier tracking into independent channels that can be optimized differently, allowing wide bandwidth for acquisition while maintaining precision during tracking through proper loop design
Solution Approach 2:
The patent implements dynamic bandwidth adjustment where the loop bandwidth is not fixed but adapts based on signal conditions and tracking state. During acquisition, wider bandwidth is used to capture large Doppler shifts, then bandwidth is reduced for precision tracking. The vector tracking loop dynamically adjusts filter bandwidths based on signal-to-noise ratio and Doppler rate to optimize both acquisition capability and tracking precision
2Speed
If a shorter integration time is used to track signals in high dynamic environment, then Doppler frequency shift changes can be followed, but loop signal to noise ratio decreases and tracking precision worsens
Solution Approach 1:
The patent merges multiple short integration intervals into a longer effective integration period through the vector tracking loop structure. By combining code phase tracking, code rate tracking, and carrier phase tracking from multiple satellites into a unified vector solution, the system achieves precision equivalent to longer integration times while maintaining short individual integration intervals to track rapid Doppler changes
Solution Approach 2:
The patent implements continuous tracking using multiple satellites simultaneously, where the vector tracking loop continuously processes signals from all visible satellites. This continuous multi-satellite processing maintains effective signal-to-noise ratio over extended periods even with short individual integration times, as the combined information from multiple satellites provides continuous constraint on the receiver position and velocity
3Device complexity
If traditional scalar tracking loops are used, then device complexity is low, but tracking sensitivity is insufficient in weak signal environments
Solution Approach 1:
The patent implements a vector tracking loop that serves multiple functions simultaneously: it performs code tracking, carrier tracking, pseudorange measurement, pseudorange rate measurement, and navigation solution all within a unified framework. This multi-functional approach replaces multiple separate scalar tracking loops, maintaining relatively simple structure while significantly improving tracking sensitivity in weak signal environments through the combined use of multiple measurement types
Solution Approach 2:
The patent introduces an extended Kalman filter as an intermediary that processes measurements from multiple satellites and multiple measurement types (pseudorange, pseudorange rate, carrier phase). This intermediary optimally combines the measurements to produce accurate position and velocity estimates, enabling the system to achieve high tracking sensitivity without requiring complex individual tracking loops for each measurement type
Data Source
AI summary
The present invention discloses a joint non-coherent integral vector tracking method based on a spatial domain, which is used for further improving the performance of a vector tracking GPS (Global Positioning System) receiver. In a new vector tracking strategy design, a phase discriminator/a frequency discriminator in a traditional vector tracking loop is discarded, and baseband signals of visible satellites in each channel are taken as an observation value after performing non-coherent integration, and EKF (abbreviation of Extended Kalman Filter) is used to estimate directly and to solve the position, the velocity, a clock error, etc. of the GPS receiver. Because of the existence of non-coherent integral calculation, when GPS satellite signals are relatively weak, a carrier to noise ratio of an observation value may be effectively improved, and the tracking sensitivity is improved.