Multiport Amplifier Calibration for Gain and Phase Imbalance
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Solution Overview
Problem
Communication satellites face calibration drift over time, especially in harsh space conditions, requiring frequent recalibration to maintain signal integrity, which is challenging without disrupting active user signals.
Innovation Solution
The use of a spread spectrum calibration signal with a power level below the thermal noise floor allows for continuous calibration of satellite channels during active operation, using a multi-step calibration process and path-to-path calibration to adjust gain, phase, and delay parameters, and applying these techniques to both beamforming and non-beamforming systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods are used, then calibration accuracy can be maintained, but user signals are disrupted during recalibration
Solution Approach 1:
The patent introduces a calibration signal as an intermediary that is injected into the signal path to enable calibration measurements without disrupting user signals. The calibration signal is separated and processed independently, allowing calibration to proceed while user communication continues uninterrupted.
Solution Approach 2:
The calibration process is performed periodically by injecting calibration signals at scheduled intervals rather than requiring continuous disruption. This allows the system to maintain calibration accuracy while minimizing impact on user signal transmission by conducting calibration measurements during designated time windows.
2Reliability
If frequent recalibration is performed to maintain signal integrity, then calibration accuracy is preserved, but system complexity and operational disruption increase
Solution Approach 1:
The system performs self-calibration by automatically injecting and measuring calibration signals without requiring external intervention or complex calibration equipment. The calibration process is integrated into the existing signal path, allowing the system to maintain its own calibration status using built-in resources.
Solution Approach 2:
The calibration signal path shares the same hardware infrastructure as the user signal path, allowing the same amplifiers, filters, and transmission lines to serve both calibration and user communication functions. This multi-functionality reduces the need for separate dedicated calibration equipment and simplifies the overall system architecture.
3Measurement precision
If high precision gain, phase, and delay stability is required, then beamforming accuracy is maintained, but hardware specifications and costs increase
Solution Approach 1:
The system uses calibration measurements to generate feedback that adjusts the gain, phase, and delay parameters of the signal paths. By continuously measuring actual performance and applying corrective adjustments, the system maintains beamforming accuracy without requiring hardware components to inherently possess ultra-high stability specifications.
Solution Approach 2:
Instead of relying on hardware with fixed high-stability parameters, the system dynamically adjusts electrical parameters (gain, phase, delay) based on calibration measurements. This allows the system to achieve high beamforming accuracy through software-controlled parameter adjustment rather than through expensive high-stability hardware specifications.
Data Source
AI summary
Beamforming channels of a satellite are calibrated using a low power, spread spectrum calibration signal. The power of the calibration signal is below the noise level of a user signal in an active channel, allowing channels to be calibrated while active. When calibrating the transmit side circuitry, a two-stage calibration can be used, first calibrating the output hybrid matrix, then calibrating the whole of the transmit side. To improve performance, the dwell time spend calibrating a channel can be based on the power of the user signal in the channel. A transmit probe can be used to inject a calibration signal into the receive antennae and a receive probe can be used to extract the calibration signal from the transmit antennae. To reduce frequency of calibrations, the calibrations can be based on path-to-path differences. These techniques are also applied to multiport amplifiers (MPAs).