Multipath Mitigation in Satellite Positioning via Selection Pulse Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing satellite positioning systems face significant challenges in accurately synchronizing local replicas of spreading codes due to multipath errors, particularly for BOC modulations, which result in positioning errors and require complex hardware and software solutions.
Innovation Solution
A method and circuit that generate a selection pulse indicative of the first polarity change within a chipping pulse, modulated with a pseudo-random noise code, to align the local spreading code with the received signal, effectively eliminating multipath errors by only using selected E-L pulses for discriminator feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional correlation methods are used to synchronize local replicas with received spreading codes, then positioning functionality is achieved, but multipath errors cause synchronization inaccuracies and positioning errors
Solution Approach 1:
The invention segments the correlation process by introducing early and late replicas with different delays, creating separate correlation paths that can be combined to mitigate multipath effects. The discriminator function divides the received signal into early and late components, correlating each with the local replica at different time offsets, then combining these correlations to achieve multipath-resistant synchronization.
Solution Approach 2:
The invention implements a feedback mechanism through the discriminator function that continuously monitors the correlation difference between early and late replicas. The discriminator output feeds back to adjust the local replica timing, creating a closed-loop system that converges to the correct synchronization point while rejecting multipath-induced errors through the E-L correlation difference.
2Measurement precision
If complex multipath mitigation algorithms are implemented, then positioning accuracy improves, but hardware and software complexity increases
Solution Approach 1:
The invention extracts only the essential early and late correlation components needed for multipath mitigation, discarding unnecessary processing steps. By focusing on the discrimination between early and late replicas rather than implementing full signal reconstruction or complex parameter estimation, the solution achieves multipath mitigation with minimal additional hardware and software complexity.
Solution Approach 2:
The discriminator function serves multiple purposes simultaneously: it provides timing error detection, multipath error estimation, and synchronization control all through a single correlation-based mechanism. The early-minus-late correlation structure inherently provides multipath rejection while maintaining the synchronization function, eliminating the need for separate complex mitigation algorithms.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention is related to a method and circuit for aligning a local spreading code with a spreading code in a received signal, said local spreading code and received spreading code comprising a plurality of chipping pulses having at least one polarity change within each chipping pulse and being modulated with a pseudo-random noise code, said method comprising the steps of: - generating a selection pulse modulated with said pseudo-random noise code, said pulse being indicative of one of said polarity changes within a chipping pulse of said local spreading code, said polarity change not coinciding with the start of said chipping pulse, and wherein said selection pulse is active in a region around said polarity change that does not overlap with other polarity changes, and inactive elsewhere; - correlating said modulated selection pulse with said received signal; - using the result of said correlating step for aligning said spreading code in said received signal and said local spreading code.