Phased Array Antenna Remote Calibration Using Scrambled Codes
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Solution Overview
Problem
Existing phased array antenna calibration systems face challenges in accuracy, especially when tracking moving targets, due to channel variations and the need to prevent hot spots or high radiated power density, which increases complexity and cost, particularly in space systems where regulatory compliance is strict.
Innovation Solution
A system and method that uses a remote calibration terminal to apply scrambled orthogonal codes to generate calibration beams, allowing for simultaneous calibration of multiple beams by analyzing phase and amplitude errors across all array elements, reducing peak power levels and interference, and utilizing the same RF channel for coherent detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If remote calibration is performed without on-board hardware and software resources, then cost and complexity of the PAA and satellite payload are reduced, but calibration accuracy deteriorates due to channel variations
Solution Approach 1:
The system performs preliminary calibration measurements by transmitting test signals through the communication channel before actual operation. The channel characteristics are measured and stored in advance, allowing the ground station to compensate for channel variations during calibration processing without requiring complex on-board equipment.
Solution Approach 2:
The system implements a feedback mechanism where calibration signals are transmitted from the satellite to the ground station, and the measured channel responses are fed back to adjust the beamforming weights. This closed-loop approach enables accurate calibration despite channel variations, resolving the contradiction between remote calibration and measurement precision.
2Productivity
If calibration signals are transmitted over the air, then hot spots or high radiated power density may occur, but regulatory compliance requires strict power density limits
Solution Approach 1:
The calibration process is segmented into multiple low-power transmissions rather than a single high-power transmission. The system transmits calibration signals across different frequency channels and time slots, distributing the total power density across multiple segments. This allows cumulative calibration data to be collected without creating harmful hot spots at any single location.
Solution Approach 2:
The system changes transmission parameters including frequency, time, and power level during calibration. By varying these parameters across multiple calibration measurements, the system achieves accurate calibration while ensuring that instantaneous and average power density remains within regulatory limits at all locations.
3Device complexity
If single element calibration is performed, then hardware complexity is reduced, but calibration time increases due to lower signal-to-noise ratio
Solution Approach 1:
The system merges multiple calibration measurements into a single comprehensive calibration process. By transmitting calibration signals across multiple frequency channels and combining the measurements at the ground station, the system achieves high signal-to-noise ratio calibration without requiring complex on-board hardware. The merged data from multiple channels provides robust calibration results faster than sequential single-element calibration.
4Productivity
If multiple beams are calibrated simultaneously, then calibration time is reduced, but the number of RF beamformer adjustments increases significantly
Solution Approach 1:
The ground station acts as an intermediary that performs the complex processing of multi-beam calibration data. Instead of requiring the satellite to perform NxB RF beamformer adjustments, the ground station receives calibration signals from all beams simultaneously and performs the computational work of determining calibration errors for each element across all beams. This transfers the complexity from the satellite hardware to ground-based processing.
Data Source
AI summary
Systems and methods for calibrating a phase array antenna (“PAA”) are provided. The system includes a PAA having a plurality of array elements and a remote calibration terminal. The PAA is connected to a processor unit. The PAA includes a reference beamforming network (“BFN”) for generating a reference beam and a calibration BFN for generating a calibration beam. The PAA applies a plurality of scrambled orthogonal codes to the calibration BFN to generate the calibration beam. The remote calibration terminal is configured to analyze the reference beam and the calibration beam to determine a calibration error for the PAA, the calibration error including a phase error and an amplitude error for each of the plurality of array elements of the PAA. The remote calibration terminal may be configured to measure a beam pointing error (“BPE”) of the PAA and/or a coupling between array elements.