Satellite Navigation Signal Decoy Detection via Antenna Angle Likelihood
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Solution Overview
Problem
Current methods for detecting decoyed signals in satellite navigation systems are unreliable, particularly in environments with obstacles, and can be deceived by signals with coherent Doppler effects, leading to erroneous position measurements, which poses serious risks, especially for aircraft.
Innovation Solution
A method that calculates the position and attitude of satellites using a receiver's antenna, determining elevation and azimuth angles through iterative searches of demodulated signals, and evaluates a likelihood function to detect decoyed signals by comparing the angles, enhancing the system's robustness and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If separate signal processing is used between sensors, then the device complexity is reduced, but the measurement precision and robustness of demodulation deteriorate
Solution Approach 1:
The patent merges the signal processing operations across all antenna sensors into a unified joint processing framework. Instead of processing signals from each sensor independently, the method combines the complex demodulated signals from multiple sensors and performs unified angle estimation through iterative maximization of a weighted complex sum, thereby improving measurement precision while maintaining manageable computational complexity through efficient algorithm design.
2Device complexity
If conventional detection methods are used, then the device complexity remains low, but the reliability of decoy detection deteriorates in environments with obstacles
Solution Approach 1:
The patent implements a feedback mechanism where the detected signal parameters (elevation and azimuth angles) are continuously compared against expected values derived from satellite positions and antenna attitude. The likelihood function computes a consistency metric that feeds back into the detection decision, allowing the system to adaptively identify decoys by detecting inconsistencies between measured and expected signal characteristics, thereby improving reliability without requiring complex additional hardware.
3Ease of operation
If simple signal comparison methods are used, then the ease of operation is maintained, but the ability to detect decoys with coherent Doppler effects deteriorates
Solution Approach 1:
The patent moves the detection approach from simple signal power or Doppler comparison into the angular domain by estimating elevation and azimuth angles from the antenna array signals. This dimensional transformation allows the system to detect decoys by identifying inconsistencies in the spatial signature of signals, which remains effective even when Doppler characteristics are coherent with legitimate satellites, thereby maintaining operational simplicity while improving detection capability.
Data Source
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AI summary
The method involves calculating a position of a satellite (1) in a trihedral geographical room reference frame centered on a receiver. An attitude of an antenna is determined (2) in the reference frame. An elevation and azimuthal angle of the satellite is calculated (3) on the frame. Another elevation and azimuthal angle of the satellite is determined (4) in another reference frame. A value of a likelihood function between the elevation and azimuthal angles is calculated (5). A risk of receiving decoy signals is detected (6) when the value of the likelihood function is lower than a threshold. An independent claim is also included for a signal receiver.