Satellite-Based Phased Array Calibration via Backscatter
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Solution Overview
Problem
Large phased array antennas face challenges in calibration due to the reliance on expensive and complex near and far field sensing methods, which are impractical for very large arrays, and existing calibration techniques do not effectively verify the calibrated state or detect errors caused by assembly issues or component degradation.
Innovation Solution
The use of a satellite with a known position for element and subarray level calibration, where the system transmits a beam towards the satellite, and the backscattered waves are used to measure residual errors, allowing for the calculation of calibration coefficients and achieving accurate calibration with multiple satellite passes to reduce signal noise and multipath errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If near field or far field sensing methods are used for calibration, then calibration accuracy can be achieved, but the cost and complexity increase significantly for very large arrays
Solution Approach 1:
The patent introduces a calibration satellite as an intermediary object between the phased array antenna and the calibration process. Instead of using complex near-field or far-field sensing equipment, the system uses a satellite with known position and reflector characteristics as a natural calibration target. The satellite acts as a passive reflector that provides a known reference signal for calibration, eliminating the need for expensive and complex ground-based calibration facilities.
Solution Approach 2:
The patent uses the satellite's known geometric configuration and position data to create a virtual model of the expected radar cross section. By comparing the actual received signal with the predicted signal from the satellite model, the system can determine calibration coefficients without requiring physical calibration equipment. This virtual copying of the satellite's electromagnetic characteristics enables calibration through computational comparison rather than physical measurement.
2Ease of manufacture
If conventional calibration methods are used, then initial calibration can be achieved, but verification of the calibrated state and detection of errors cannot be performed
Solution Approach 1:
The patent implements a feedback mechanism where the received signal from the satellite is compared with the predicted signal based on the satellite's known geometry and position. The difference between the actual and predicted signals provides feedback information that indicates whether calibration is correct or if errors are present. This feedback loop enables continuous verification of the calibrated state and detection of assembly errors or component degradation without requiring separate verification procedures.
3Measurement precision
If factory calibration is required for large arrays, then calibration accuracy can be achieved, but system downtime increases significantly
Solution Approach 1:
The patent enables calibration to be performed using pre-acquired satellite position and geometric data. The satellite's orbital parameters and reflector characteristics are known in advance, allowing the system to perform calibration calculations using previously collected information. This preliminary preparation of calibration data eliminates the need for time-consuming on-site calibration procedures and allows rapid calibration updates without requiring the antenna system to be taken offline for extended periods.
4Adaptability or versatility
If digital beam forming systems are used, then system capabilities are enhanced, but additional microwave connectivity calibration is required which increases complexity
Solution Approach 1:
The patent uses a universal calibration approach where the satellite-based calibration method simultaneously calibrates both the analog phased array components and the digital beam forming channels. By using the satellite as a common reference target for the entire signal path from antenna elements through analog processing to digital beam forming, the system achieves multi-functional calibration in a single procedure, eliminating the need for separate calibration processes for different system components.
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 method provides accurate array calibration at a lower cost, eliminating the need for factory calibration and allowing subarray calibration in a factory setting, with the ability to achieve high accuracy and reduce system downtime, while improving the reliability of the calibration process.
Implementation Method 1
satellite-based calibration uses a system under test to transmit a sometimes crudely formed beam towards a known high RCS satellite having an orbit position within the system field of view. The backscattered waves from the satellite illuminate the same system in receive mode.
Implementation Method 2
The backscattered waves from the satellite illuminate the same system in receive mode. The satellite projects a known amplitude and phase distribution on the system aperture.
Data Source
AI summary
Methods and apparatus to calibrate an array by sequentially calibrating elements in a subarray with respect to each other using a satellite. The satellite is repeatedly illuminated for calibrating the elements using reference elements to determine plane fronts from which active elements can be calibrated with respect to each other.