PRN Ranging Receiver Correlator Asymmetry for Multipath Mitigation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current GPS receivers face inaccuracies in range measurements due to multipath errors caused by reflected signals, which existing solutions fail to fully mitigate, especially requiring complex hardware and extensive calibration.
Innovation Solution
A pseudorandom noise ranging receiver employing non-uniformly spaced correlators and digital signal processing to estimate multipath errors by exploiting the asymmetry of the correlation function, using a wideband RF front end and multiple programmable phased correlators, thereby reducing hardware costs and calibration needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional multipath mitigation solutions (multiple narrowly-spaced correlators, complex signal processing algorithms) are used, then measurement precision is improved, but device complexity increases significantly
Solution Approach 1:
The patent applies asymmetry by using non-uniform correlator spacing instead of uniform spacing. The correlators are positioned at asymmetric intervals (e.g., 0.05 chip, 0.15 chip, 0.25 chip) to better capture the asymmetric distortion caused by multipath signals. This asymmetric arrangement enables more effective multipath error detection and mitigation without requiring a large number of correlators, thus improving measurement precision while controlling device complexity.
Solution Approach 2:
The patent segments the correlation function measurement into multiple discrete correlator outputs at different delays. By dividing the correlation measurement into segments captured by individual correlators at specific delay points, the system can reconstruct the correlation function shape and detect multipath-induced asymmetries. This segmentation approach enables complex signal analysis using simpler individual correlator elements.
2Measurement precision
If antenna-based mitigation techniques (special antennas, multi-antenna arrays) are used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical/physical antenna-based solutions with a signal processing approach using non-uniform correlator spacing. Instead of using special antennas or multi-antenna arrays (mechanical/physical solutions), the invention uses a computational method with strategically positioned correlators to achieve multipath mitigation. This substitution of mechanical systems with signal processing algorithms reduces device complexity and cost while maintaining measurement precision.
3Measurement precision
If existing multipath mitigation algorithms are implemented, then measurement precision improves, but ease of operation deteriorates due to extensive calibration requirements
Solution Approach 1:
The patent implements self-service by enabling the correlator system to automatically adapt to multipath conditions without external calibration. The non-uniform correlator spacing provides inherent capability to detect and characterize multipath signals, allowing the system to self-adjust and self-correct measurements. This eliminates the need for extensive manual calibration procedures, improving ease of operation while maintaining measurement precision.
Data Source
AI summary
This invention is directed to a method for estimating and compensating for multipath errors in a pseudorandom noise ranging receiver. The method exploits the asymmetry of the correlation function and proportionately relates it to the magnitude of multipath error. In a pseudorandom noise ranging receiver, the correlation function is obtained by generating the local pseudorandom noise sequences at different programmed non-uniform phases resulting in non-uniformly spaced correlators. Numerically controlled oscillators, code generators and shift registers are programmed to determine the correlation values at non-uniformly distributed points on a correlation function. Curve fitting is undertaken to determine the code phase at which the correlation function peaks. A proportionality constant is applied to the measure of asymmetry of the correlation function to determine the multipath error in the pseudorandom noise signal. A filter is used to detect and eliminate outliers.