Coherent Matched Filter Receiver for Weak ADS-B Signal Recovery
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Solution Overview
Problem
Existing terrestrial ADS-B receivers face challenges in detecting and receiving 1090 MHz Mode S ES ADS-B messages from aircraft due to interference, noise, and the near-far problem, and these issues are exacerbated in space-based receivers due to greater propagation distances and higher volumes of messages.
Innovation Solution
A receiver design that includes an analog-to-digital converter, a carrier detection module, a cross-correlation module, a signal estimator module, a screening module, a carrier refinement module, and a coherent matched filter, which together process the received signal to detect and recover 1090 MHz Mode S ES ADS-B messages by utilizing expected pulse patterns and multi-layer screening techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If terrestrial ADS-B receiver design is used for space-based operations, then infrastructure coverage is improved, but signal-to-noise ratio deteriorates due to increased propagation distance
Solution Approach 1:
The patent applies preliminary action by performing carrier detection and cross-correlation operations before the coherent matched filter processing. The system detects carrier presence and estimates signal parameters in advance, which prepares the receiver to properly process weak signals from space-based operations, thereby improving signal-to-noise ratio while maintaining wide coverage area
Solution Approach 2:
The patent changes operational parameters by implementing a coherent matched filter that is phase-matched to the desired phase, and by adjusting carrier frequency and phase alignment based on detected signal characteristics. These parameter adjustments optimize the receiver's ability to detect weak signals from distant aircraft, resolving the contradiction between coverage area and signal-to-noise ratio
2Measurement precision
If signal processing complexity is increased to improve detection in low signal-to-noise ratio, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the signal processing into distinct functional modules: carrier detection module, cross-correlation module, signal estimator module, screening module, and coherent matched filter. Each module performs a specific function in sequence, which improves detection accuracy through systematic processing while managing device complexity through modular architecture
Solution Approach 2:
The patent performs preliminary signal characterization through carrier detection and cross-correlation before applying the coherent matched filter. This preliminary action extracts essential signal parameters (frequency, phase, timing) that simplify subsequent processing and improve detection accuracy without requiring excessively complex real-time processing
3Measurement precision
If carrier detection and cross-correlation processing is performed, then message detection accuracy is improved, but processing time increases
Solution Approach 1:
The patent performs carrier detection and cross-correlation as preliminary operations before the main coherent matched filter processing. By detecting carrier presence and estimating signal parameters in advance, the system reduces the computational burden of subsequent message recovery, improving detection accuracy while minimizing additional processing time
Solution Approach 2:
The patent introduces intermediate processing stages (carrier detection module, cross-correlation module, signal estimator) that act as mediators between the raw received signal and the coherent matched filter. These intermediary modules prepare the signal by extracting key characteristics, which accelerates the main detection process while maintaining high message detection accuracy
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed receiver design effectively detects and recovers 1090 MHz Mode S ES ADS-B messages from space, improving signal processing accuracy and reducing error rates despite the challenging noise and interference environments.
Implementation Method 1
a cross-correlation module configured to calculate, responsive to a determination by the carrier detection module that a spectral component within the range of 1090 MHz is present within the portion of the digital representation of the received signal, a measure of the cross-correlation between the portion of the digital representation of the received signal and a reference signal representing an expected pulse pattern
Implementation Method 2
a coherent matched filter that is phase-matched to the desired phase and configured to recover a 1090 MHz Mode S ES ADS-B message from the digital representation of the received signal
Implementation Method 3
a carrier refinement module configured to shift the frequency of carrier pulses in the digital representation of the received signal toward a desired frequency and to align the phase of carrier pulses in the digital representation of the received signal with a desired phase
Data Source
AI summary
In one implementation, a receiver has a module to calculate the cross-correlation between a portion of a digital representation of a received signal and a reference signal. 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 and a screening module to determine the likelihood that the received signal includes a message. For a received signal that is determined likely to include a message, the receiver includes a carrier refinement module to shift the frequency of carrier pulses in the digital representation of the received signal toward a desired frequency and to align the phase of carrier pulses in the digital representation of the received signal with a desired phase and a coherent matched filter to recover the message from the digital representation of the received signal.