Satellite Beamforming Network Calibration via Orthogonal Coding
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Solution Overview
Problem
Existing satellite communication systems face challenges in maintaining stable gain and phase tracking performance over long signal paths, especially at high frequency bands, leading to degradation of Equivalent Isotropically Radiated Power (EIRP) and isolation performance due to uncompensated drifts in beamforming networks (BFN), which current calibration methods fail to address effectively.
Innovation Solution
A calibration method that characterizes and corrects tracking drifts in the output section of a satellite payload's BFN using an orthogonal, bipolar, invertible matrix to encode calibration signals, allowing for deterministic measurement and prediction of gain and phase changes, enabling in-orbit re-characterization and adjustment of beamforming network settings to maintain performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single-element calibration techniques are used, then calibration can be performed, but measurement time becomes excessively long and accuracy is insufficient
Solution Approach 1:
The calibration process is segmented into multiple parallel measurements using different orthogonal codes assigned to different antenna elements. Instead of calibrating elements sequentially, the system divides the calibration task across multiple simultaneous measurements, each using a unique orthogonal code signature, thereby reducing total measurement time while maintaining accuracy through parallel data collection
Solution Approach 2:
The system employs periodic transmission of orthogonal coded sequences across antenna elements in a systematic pattern. By periodically cycling through different code assignments and measuring the combined responses, the system efficiently extracts individual element characteristics through correlation processing, achieving accurate calibration in reduced time compared to traditional sequential methods
2Measurement precision
If COS calibration operations are performed to optimise end-to-end payload performance, then antenna element calibration is improved, but the BFN itself remains uncalibrated and performance drifts occur
Solution Approach 1:
The system introduces a dedicated calibration signal path that acts as an intermediary reference, injecting known test signals through the BFN to directly measure and characterize BFN performance. This intermediary calibration approach independently verifies BFN gain and phase responses without being confounded by antenna element variations, enabling separate BFN calibration and drift compensation
Solution Approach 2:
The calibration system implements feedback by continuously monitoring BFN performance through injected test signals and using the measured responses to update compensation parameters. The system feeds back correction data to adjust BFN settings, compensating for drifts in gain and phase responses over time and across temperature variations, thereby maintaining reliable BFN operation
3Volume of moving object
If low-power beamforming networks are used for size and technology reasons, then satellite payload size is reduced, but signal path length increases causing degraded gain and phase tracking
Solution Approach 1:
The system performs preliminary characterization of the signal path during calibration operations, measuring and storing the gain and phase responses of each path before actual payload operation. By pre-measuring the effects of long signal paths and storing compensation parameters, the system can later apply corrections to maintain accurate beamforming performance despite the extended path lengths necessitated by compact low-power BFN design
Solution Approach 2:
The calibration system dynamically adjusts and updates the gain and phase parameters of the BFN based on measured performance drifts. By continuously monitoring actual signal path characteristics and modifying the complex gain parameters accordingly, the system compensates for degradations caused by long signal paths, maintaining precise beamforming control within the constraints of compact low-power hardware
Data Source
AI summary
Disclosed are a calibration system and method for correction of tracking drifts in the output section of a satellite payload and a beamforming network. The disclosed technique exploits characterisation of path gain and phase tracking drifts as deterministic errors that can be measured over spacecraft lifetime without statistical approximations, and thereafter predicted for in-orbit daily temperature variations. Also disclosed is a satellite payload for transmitting test signals to the calibration system.