Satellite Carrier Phase Loop Delay Compensation for Stable Tracking
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Solution Overview
Problem
Current satellite radio-navigation receivers face instability in the carrier phase loop due to delays in software computation and NCO homing, leading to reduced dynamic resistance and increased noise sensitivity, which affects the accuracy and robustness of signal tracking.
Innovation Solution
A device with a modified carrier loop feedback system that compensates for delays through advanced phase discrimination and filtering, using a software portion that calculates a compensation term based on previous phase and acceleration data to stabilize the loop operation, allowing for increased loop bandwidth without altering the pre-detection band or workload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If software computation and NCO homing delays are present in the carrier phase loop, then the loop can operate with standard software architecture, but the loop becomes unstable and dynamic resistance is reduced
Solution Approach 1:
The patent applies preliminary action by calculating and applying a compensation term in advance to counteract the known delays in software computation and NCO homing. The compensation term is computed based on predicted phase values before the actual measurement is taken, allowing the system to pre-correct for the inevitable delays in the feedback loop processing chain.
Solution Approach 2:
The patent implements feedback by using the output of the phase discriminator to generate a compensation term that is fed back into the correlation process. This closed-loop feedback mechanism continuously adjusts the compensation based on the measured phase error, stabilizing the carrier phase loop despite the presence of software computation delays.
2Reliability
If loop bandwidth is increased to improve dynamic resistance, then tracking accuracy improves, but noise sensitivity increases
Solution Approach 1:
The patent applies parameter changes by modifying the effective loop bandwidth through the compensation mechanism. By introducing the compensation term, the system can operate with a wider loop bandwidth to improve dynamic resistance while the compensation effectively filters out the high-frequency noise that would normally be amplified by the wider bandwidth, thus changing the noise characteristics of the system.
3Object-affected harmful factors
If pre-detection band is reduced to improve signal-to-noise ratio, then noise robustness improves, but loop bandwidth must be reduced affecting dynamic resistance
Solution Approach 1:
The patent applies segmentation by separating the noise filtering function from the bandwidth limiting function. The compensation term handles the phase correction independently, allowing the pre-detection band to be narrowed for noise robustness while the compensation mechanism maintains the effective loop response speed, dividing the functions into independent processing stages.
Data Source
AI summary
Described is a device for receiving radio-navigation signals by satellite, said received signals being transmitted at a carrier frequency. The device includes at least means for generating a local signal at a local frequency and a tracking device including a feedback loop called carrier loop for phase-locking the local frequency on the carrier frequency. The loop includes a hardware portion and a software portion. The software portion performs the functions of discrimination of the phase of the correlated signal and filtering of said phase. The software portion also includes correlation functions mainly dependent on the linear variation coefficients between the local phases φlocal delivered after each basic computation cycle. The device makes it possible to increase the loop band and the dynamic stability without changing the pre-detection band and the workload of the software.