AESA Mutual Coupling Compensation via Near-Field Probe Calibration
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Solution Overview
Problem
Active electronically scanned arrays (AESA) face performance degradation due to mutual coupling between antenna elements, which conventional techniques struggle to address effectively without increasing cost or violating size, weight, and power constraints, and require time-consuming measurements using specialized hardware.
Innovation Solution
A calibration system that uses a probe to indirectly measure mutual coupling effects, generating correction factors to construct a correction matrix that compensates for mutual coupling without direct measurement of currents and voltages at element terminals, allowing for improved signal processing to approximate ideal output vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If antenna elements are placed in close proximity to reduce array size, then array size is reduced, but mutual coupling between elements increases causing performance degradation
Solution Approach 1:
A probe is introduced as an intermediary element to measure the near-field signals radiated by array elements. The probe indirectly characterizes mutual coupling effects by measuring radiated fields in the near-field region, avoiding the need for direct terminal measurements while enabling correction factor computation
Solution Approach 2:
The patent changes the measurement parameter from direct terminal voltages/currents to near-field radiated signal measurements. By measuring the near-field signals at multiple positions and processing them through signal processing techniques, the system derives mutual coupling information without direct electrical contact with element terminals
2Measurement precision
If conventional measurement techniques are used to characterize mutual coupling, then measurement precision is improved, but device complexity and cost increase due to multi-port network analyzers
Solution Approach 1:
Instead of using complex multi-port network analyzers to directly measure terminal parameters, the patent uses a simple probe to copy or replicate the measurement function by sensing near-field signals. The probe creates a simplified measurement system that indirectly captures mutual coupling effects through radiated field measurements
Solution Approach 2:
The patent replaces the mechanical/electrical measurement system (multi-port network analyzer with direct terminal connections) with an electromagnetic field-based measurement system (probe measuring near-field signals). This substitution simplifies the measurement hardware while maintaining measurement capability through field-based indirect measurement
3Loss of information
If simultaneous measurements of currents and voltages in each element are performed, then measurement completeness is improved, but measurement time increases
Solution Approach 1:
The patent uses periodic excitation of array elements (transmitting signals from each element in sequence) and corresponding periodic probe measurements. By systematically exciting each element and measuring the near-field response, the system collects complete mutual coupling information through a structured time-sequence measurement process
Solution Approach 2:
The patent performs preliminary near-field measurements during the calibration phase to characterize mutual coupling effects before actual operation. These preliminary measurements establish correction factors that are then applied during normal operation, eliminating the need for repeated time-consuming measurements
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
This approach enhances AESA performance by correcting for mutual coupling without hardware modifications or the need for costly measurement tools, maintaining compliance with platform constraints and improving beam steering capabilities.
Implementation Method 1
a probe is used to indirectly measure signals indicative of mutual coupling between elements of an array during transmission. The signals are received at a plurality of near-field positions each aligned with a respective element in the array
Data Source
AI summary
Technologies pertaining to the calibration of ultra-wide-band active-electronically-scanned arrays to compensate for transmit and receive mutual coupling between array elements and/or non-ideal isolated channels are described herein. A plurality of near-field measurements are taken by way of probe or probes that may be moved among a plurality of positions aligned with respective elements in the array. For each position of the probe, each of the elements of the array is stimulated to transmit or receive a calibration signal to or from the probe, respectively. Frequency-domain transfer functions are computed from the received signals by the probe or the element for each of the array elements in each of the positions of the probe. The inverse of the matrix of transfer functions comprise frequency-domain transmit and receive correction factors that are used to modify desired array inputs/outputs such that the modified signals correct for mutual coupling between elements in the array.