AESA Hybrid Calibration for Low Side Lobe Error Correction
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Solution Overview
Problem
Current AESA calibration techniques for low side lobe operation are inefficient due to reliance on single gain and phase tables, which result in residual errors and require expensive, time-consuming near field or far field range testing, limiting throughput and precision.
Innovation Solution
A calibration system that performs initial calibration using known methodologies, followed by near field measurements to compute phase and amplitude error maps, adjusting T/R module settings iteratively until desired precision is reached, combining near and far field radiation patterns and hologram back projection for accurate corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional single gain and phase table calibration is used, then calibration process is simple, but residual gain and phase errors remain and low side lobe precision is insufficient
Solution Approach 1:
The patent divides the calibration process into multiple stages: initial calibration using RFIC datasheet values, followed by near field measurements to generate holograms, then iterative back-projection to compute correction coefficients. This segmentation allows achieving high precision (within tenths of dBs in amplitude and a few degrees in phase) without requiring complex single-step calibration systems.
Solution Approach 2:
The patent performs preliminary near field measurements and hologram generation before final calibration coefficient computation. By pre-characterizing the aperture field distribution and computing error maps in advance, the system prepares correction data that compensates for passive RF circuitry variations, enabling precise low side lobe operation without during-operation complexity.
2Measurement precision
If near field or far field range testing is used for accurate calibration, then calibration precision is improved, but calibration time increases from minutes to hours and cost increases
Solution Approach 1:
The patent uses near field holographic copies of the far field radiation pattern to perform calibration. By measuring in the near field and mathematically back-projecting to obtain far field equivalent data, the system achieves far field calibration accuracy without requiring actual far field range facilities or lengthy measurement times, reducing calibration to minutes rather than hours.
Solution Approach 2:
The patent replaces mechanical far field range testing systems with computational back-projection methods. Instead of physically moving antennas through large far field ranges or using complex mechanical alignment systems, the system uses near field measurements combined with mathematical algorithms to compute calibration coefficients, eliminating expensive infrastructure and time-consuming mechanical operations.
3Measurement precision
If repetitive full near field scans are performed for holographic back projection calibration, then calibration accuracy is improved, but calibration time increases to approximately 1 hour per scan
Solution Approach 1:
The patent performs preliminary near field measurements to generate aperture holograms before iterative back-projection calibration. By pre-acquiring the complete near field data set and computing initial error maps, the system prepares all necessary measurement information in advance, enabling subsequent iterative coefficient optimization to proceed rapidly without repeated physical scanning, thus maintaining high accuracy while improving throughput.
4Measurement precision
If far field anechoic chambers or compact ranges are used for calibration, then calibration accuracy is achieved, but facility cost, footprint, and calibration time increase
Solution Approach 1:
The patent creates computational copies of far field radiation patterns through near field holographic measurements and back-projection algorithms. This approach eliminates the need for physical far field anechoic chambers or compact ranges, achieving the same measurement accuracy in a compact near field setup that requires minimal facility footprint and can be implemented in production environments.
Data Source
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AI summary
A calibration system (100) for AESAs induces the AESA to produce a far field radiation pattern while near field measurements are taken; an initial calibration is produced, and complex aperture holograms are calculated. Based on the complex holograms, phase and amplitude error maps are computed. T / R module amplitude and phase are then adjusted to compensate for the error map. The system (100) evaluates the refined far field radiation pattern to iteratively recompute complex aperture excitations to realize adequate far field performance and new hologram error maps until a desired level of precision is reached.