Non-Coherent Matched Filtering for Low-SNR ADS-B Receivers
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Solution Overview
Problem
Existing terrestrial ADS-B receivers are incapable of achieving satisfactory performance for space-based operation due to the low signal-to-noise ratio (SNR) of ADS-B messages received in low-Earth orbit, requiring a higher SNR than terrestrial receivers to maintain a 10% bit error rate, which is not feasible with current designs.
Innovation Solution
A receiver design that includes an analog-to-digital converter, carrier detection module, cross-correlation module, signal estimator, and non-coherent matched filter to process and recover 1090 MHz Mode S ES ADS-B messages, utilizing cross-correlation and multi-layer screening techniques to enhance detection accuracy in low SNR conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If terrestrial ADS-B receiver design is used for space-based operation, then device complexity is reduced, but signal-to-noise ratio performance deteriorates
Solution Approach 1:
The patent modifies the receiver design by implementing a non-coherent matched filter that operates without carrier phase synchronization, changing the operational parameters from coherent to non-coherent detection. This adaptation allows the receiver to maintain reliability in space-based low-SNR environments while managing device complexity through optimized signal processing algorithms
2Measurement precision
If coherent detection is used, then measurement precision is improved, but adaptability to low SNR conditions deteriorates
Solution Approach 1:
The patent inverts the conventional approach by using non-coherent detection instead of coherent detection. This inversion sacrifices some measurement precision in ideal conditions but gains superior adaptability to low SNR space-based environments, where carrier phase synchronization is difficult to maintain
3Device complexity
If traditional signal processing is used, then device complexity is minimized, but detection accuracy in low SNR conditions deteriorates
Solution Approach 1:
The patent applies preliminary signal processing actions including matched filtering and multi-layer screening before final detection. These preliminary operations enhance the signal quality and feature extraction in low-SNR conditions, improving detection accuracy while keeping the overall device complexity manageable through efficient algorithm implementation
Data Source
AI summary
In one implementation, a receiver has a module to detect a carrier within a portion of a digital representation of a received signal. In addition, the receiver includes a module to calculate the cross-correlation between the portion of the digital representation of the received signal and a reference signal representing an expected pulse pattern. The receiver also has a module to generate an estimate of a portion of a message potentially included in the digital representation of the received signal. The receiver further includes a screening module to generate a feature vector representing the estimated message, project the feature vector into a feature space, and determine the likelihood that the digital representation of the received signal includes a message. If the digital representation of the received signal likely includes a message, the receiver includes a non-coherent matched filter to recover the message from the digital representation of the received signal.