Mitigating Array Factor Distortions in Adaptive GPS Antennas
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Solution Overview
Problem
GPS signal reception systems face performance limitations due to array factor distortions caused by changes in antenna attitude and position, which affect the quality and accuracy of signal reception, particularly in high-performance applications like airborne GPS systems.
Innovation Solution
An adaptive antenna system with array factor mitigation, which includes input ports coupled to an array antenna, an adaptive processor, a combiner configuration, and an array aiding processor that provides weighting information and predictive angle values to correct for array factor distortions, thereby mitigating signal reception variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an adapted antenna pattern is used to reduce jamming and interference, then reliability of signal reception is improved, but array factor distortions cause variations in amplitude, phase and group delay that deteriorate measurement precision
Solution Approach 1:
The system pre-calculates and stores array factor distortion data for various arrival angles and adapted antenna patterns before signal reception. During operation, the array aiding processor retrieves pre-computed correction signals based on the current adapted pattern and signal arrival angle, eliminating the need for real-time distortion calculation and enabling rapid correction application
Solution Approach 2:
The array aiding processor continuously monitors the adapted antenna pattern characteristics and signal arrival angle, then applies correction signals to compensate for array factor distortions. This closed-loop feedback mechanism ensures that distortion corrections are dynamically adjusted to match current operating conditions, maintaining measurement precision while preserving the jamming rejection benefits of the adapted pattern
2Reliability
If adaptive processing is used to steer receiving pattern nulls to interference signals, then reliability is improved, but device complexity increases due to additional processors and data facilities
Solution Approach 1:
Array factor distortion data and correction signals are pre-calculated and stored in data facilities before actual signal reception occurs. The system prepares correction tables for various adapted antenna patterns and arrival angles in advance, so that during operation the array aiding processor only needs to retrieve and apply pre-computed corrections rather than performing complex real-time calculations
Solution Approach 2:
The array aiding processor acts as an intermediary component that bridges the adaptive processor and the signal reception system. It receives information about the current adapted pattern and signal arrival angle, then provides correction signals without requiring direct complex interactions between the adaptive processor and the rest of the signal processing chain, thereby simplifying the overall system architecture
Data Source
AI summary
An adaptive antenna system may be used with a GPS system to improve operation in the presence of interference signals. A resulting adapted antenna pattern will cause array pattern distortions affecting GPS satellite signals received at some signal arrival angles. By determining values of array factor distortions applicable to a GPS satellite signal received at a specific arrival angle via a specific adapted array pattern, a correction signal may be developed for use to mitigate the effect of the applicable array factor distortion. By use of satellite angle data, navigational data, or both, a predictive angle value of a future arrival angle of a satellite signal may be identified. By developing a correction signal applicable to that future arrival angle, corrections for arriving signals can be applied without reliance on stale values. Corrections may be made to the received satellite signal or may be supplied to the GPS system for corrective use during processing of the received signal. Other systems and methods applicable to reception of GPS, broadband or other signals via array antennas with or without adaptive processing are also described.