Correction Phase Locked Loop for Multipath Error Suppression
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Solution Overview
Problem
Multipath errors caused by reflected signals significantly reduce the accuracy of code and carrier phase measurements in navigation receivers, which existing methods struggle to effectively suppress, especially considering the interplay of various disturbances.
Innovation Solution
A PLL system with a primary phase error calculator and phase corrector, including a correction correlator and discriminator, is introduced to generate and correct error signals, using parallel circuits to suppress delayed reflected signals and improve frequency-phase control, enhancing the signal processing unit's ability to handle multipath errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PLL tracking is used, then the receiver can track carrier frequency, but multipath errors significantly reduce measurement accuracy
Solution Approach 1:
The error signal calculation is segmented into two independent paths: a primary path that processes all correlation signals normally, and a correction path that specifically processes differential quadrature correlation signals to isolate multipath errors. This segmentation allows the system to identify and correct multipath-induced phase errors without affecting the overall tracking functionality.
Solution Approach 2:
A correction discriminitor is introduced as an intermediary component that specifically processes the differential quadrature correlation signal to extract multipath error information. This intermediary then feeds correction signals to the primary phase error calculator, acting as a mediator that isolates and eliminates multipath effects from the final phase measurement.
2Measurement precision
If multipath suppression methods are applied, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The correction correlator and correction discriminitor are designed to process the same correlation signals already generated for normal tracking, making them multi-functional components. The differential quadrature correlation signal is extracted from existing signal paths without requiring separate dedicated hardware, thereby reducing the increase in device complexity while still achieving multipath suppression.
3Object-affected harmful factors
If correction correlator and discriminitor are added, then multipath errors are suppressed, but processing complexity increases
Solution Approach 1:
The system performs preliminary processing of the differential quadrature correlation signal in the correction correlator before it is needed for multipath correction. By pre-calculating and preparing the correction signal based on already-available correlation data, the system avoids complex real-time processing during the critical tracking phase, thereby reducing processing complexity while maintaining effective multipath suppression.
Data Source
AI summary
A correction phase locked loop (CPLL), including a signal processing unit that receives a digitized input signal from a satellite, the signal processing unit comprising (a) a primary correlator and primary discriminator, connected in series and generating a main error signal Z1 from the digitized input signal; (b) a correction correlator and a correction discriminator connected in series and generating a correction signal Z2; and (c) an adder for adding the main error signal Z1 and the correction signal Z2 to produce a common error signal Z. A loop filter filters the common error signal Z to produce a corrected error signal that is used for frequency-phase control of a Numerical Control Oscillator (NCO). The NCO generates two mutually orthogonal output reference signals whose phase is substantially free of multipath errors.