Cascaded GNSS Electronic Protection for Weak and Strong Interference
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Solution Overview
Problem
Traditional digital beam-forming electronic protection systems in navigation systems are ineffective in mitigating weak interference sources, such as spoofing and meaconing, which operate below the thermal noise floor, while effectively addressing strong interference.
Innovation Solution
A cascaded electronic protection system that combines multi-stream post-correlation spatial filtering and pre-correlation temporal filtering within the GNSS receiver, utilizing covariance estimates and autocorrelation estimates to calculate optimal spatial and temporal weights for null formation against undesired emitters, thereby mitigating both weak and strong interference sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional digital beam-forming electronic protection systems are used, then strong interference is effectively mitigated, but weak interference sources below the thermal noise floor cannot be mitigated
Solution Approach 1:
The electronic protection system is segmented into two independent but cascaded stages: a pre-correlation temporal filtering stage for strong interference mitigation, and a post-correlation spatial filtering stage for weak interference mitigation. Each stage operates with its own processing chain and optimization criteria, allowing specialized handling of different interference types without compromising the other.
Solution Approach 2:
The pre-correlation temporal filtering stage performs preliminary mitigation of strong interference sources before the correlation process. By removing or attenuating strong jammers in the temporal domain before correlation, the system prepares the signal environment for subsequent detection and mitigation of weaker interference sources that would otherwise be masked by thermal noise and strong interference.
2Measurement precision
If post-correlation spatial filtering is applied to mitigate weak interference, then measurement fidelity is maintained, but strong interference mitigation capability may be compromised
Solution Approach 1:
The system transitions from single-dimension temporal filtering to two-dimensional space-time filtering by incorporating spatial filtering in the post-correlation stage. The post-correlation spatial filtering operates in the spatial domain across multiple antenna elements, creating a complementary dimension to the temporal filtering stage. This dimensional expansion enables the system to address weak spatially-correlated interference while preserving strong interference mitigation through the temporal domain processing.
Solution Approach 2:
The correlation process acts as an intermediary between the pre-correlation temporal filtering stage and the post-correlation spatial filtering stage. By performing correlation before spatial filtering, the system transforms the signal representation in a way that enables effective spatial processing of weak interference while the earlier temporal filtering has already removed strong interferers, allowing both stages to function effectively.
3Device complexity
If a single filtering stage is used, then device complexity is reduced, but the system cannot simultaneously mitigate both weak and strong interference
Solution Approach 1:
The filtering system is segmented into distinct functional blocks: pre-correlation temporal filtering with its own weight computation, the correlation engine, and post-correlation spatial filtering with separate weight computation. This segmentation allows each stage to be optimized independently for its specific interference type while maintaining overall system manageability and modular complexity.
Solution Approach 2:
The cascaded filtering system achieves multi-functionality by combining temporal and spatial filtering capabilities in a unified processing chain. The same hardware architecture supports both strong interference mitigation through temporal filtering and weak interference mitigation through spatial filtering, making the system versatile against diverse interference threats without requiring separate dedicated systems.
Data Source
AI summary
An adaptive cascaded electronic protection processing system for global navigation satellite system (GNSS) threat mitigation is provided. The system includes a precorrelation characterization component configured to provide at least one parameter characterizing a plurality of received signals. A correlator is configured to provide a plurality of correlation results, each representing one of the plurality of received signals. A spatial weight contribution component is configured to determine an optimal set of digital beam-forming weights via an optimization process according to the at least one parameter. A postcorrelation characterization component is configured to determine at least one constraint on the optimization process according to the plurality of correlation results.