Multi-Stage Filter Bank for GPS Narrowband Interference Mitigation
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Solution Overview
Problem
Current GPS receiver systems are vulnerable to narrowband interference, such as jamming signals, which can degrade or prevent GPS signal reception due to their reliance on direct spread spectrum coding, and existing interference mitigation techniques are not optimized for frequency agile jammer signals or 'chirp' type wavelets, requiring complex designs with many transformers and fixed scaling.
Innovation Solution
A method and system that utilize a multi-stage filter bank to decompose RF signals into sub-bands, scale each stage for separating desired and interference signals, suppress interference by zeroing outputs exceeding a threshold, and reconstruct the signal, allowing for adaptive time and frequency resolution adjustments to improve filtering performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dyadic filter with fixed scaling is used to suppress frequency-shifting jamming signals, then suppression effectiveness is improved, but the number of stages required increases and the system cannot efficiently process frequency agile or chirp type jammer signals
Solution Approach 1:
The patent implements dynamic scaling factors that adapt to the actual frequency characteristics of jamming signals. Instead of fixed scaling, the system calculates scaling factors based on measured frequency offsets and applies them stage-by-stage to track and suppress frequency-agile and chirp type jammers effectively
Solution Approach 2:
The system changes the scaling parameters dynamically based on the detected jamming signal characteristics. By adjusting scaling factors according to measured frequency offsets, the filter can adapt to different types of jamming signals (frequency-shifting, frequency-agile, chirp) without requiring a fixed large number of stages
2Measurement precision
If the number of wavelet transform stages is increased to isolate interference signals, then interference isolation capability is improved, but the computational complexity and number of transformers required increases significantly
Solution Approach 1:
The patent segments the frequency spectrum into multiple sub-bands using a filter bank structure. By dividing the broad frequency range into narrower sub-bands and processing each independently with appropriate scaling, the system achieves precise interference isolation with fewer total transformers compared to a single deep wavelet transform
3Power
If direct spread spectrum coding is used to enable GPS signal processing below the noise floor, then signal processing capability is improved, but vulnerability to narrowband interference increases
Solution Approach 1:
The patent converts the harmful narrowband interference into a detectable and suppressible artifact by exploiting its concentrated spectral characteristics. The interference mitigation system identifies narrowband components in the frequency domain and selectively removes them, transforming the harmful effect into a controlled processing step that preserves the spread spectrum signal
Data Source
AI summary
A system and method for mitigating interference of a radio frequency (RF) signal includes a receiver configured to include: a decomposition module that decomposes a received RF signal into sub-bands via a multi-stage filter, each sub-band being configured to operate on real and imaginary components of the RF signal, and each stage being scaled for separating time-frequency content of the desired signal from time-frequency content of the interference; a mitigation module that suppresses the interference of the RF signal in each sub-band by zeroing an output of a respective sub-band when the frequency content exceeds a predetermined threshold; and a reconstruction module that reconstructs the RF signal from the mitigation module minus the interference. The receiver is configured to determine whether the multi-stage filter is to be reinitialized with updated time and frequency resolution requirements to improve system response.