Power Amplifier Gain and Phase Control Without Long Calibration
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Solution Overview
Problem
Conventional power amplifier control systems in communications satellites require lengthy calibration procedures due to nonlinearity issues, which can take up to 48 hours, and are ineffective for amplifiers with hysteresis-type memory effects.
Innovation Solution
A control system with separate gain and phase control loops that adjust the input signal based on real-time measurements of the amplified signal, using a feed-forward loop to minimize error signals and account for operational history, eliminating the need for calibration and improving response time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If open-loop control with lookup table is used to compensate for nonlinearity, then gain and phase predistortion can be applied, but the calibration procedure becomes extremely lengthy (up to 48 hours)
Solution Approach 1:
The patent implements closed-loop feedback control by measuring the actual output signal from the power amplifier and comparing it with the desired output. The error signal is fed back to continuously adjust the gain and phase control, eliminating the need for lengthy open-loop calibration procedures while maintaining accurate control of the amplified signal
Solution Approach 2:
The control system performs self-adjustment by automatically measuring its own output performance and correcting errors in real-time. The system uses internal detectors and processors to monitor and adjust gain and phase without requiring external calibration equipment or procedures, enabling rapid system setup and adaptation
2Adaptability or versatility
If conventional control systems are used, then they can control linear amplifiers, but they are ineffective for amplifiers with hysteresis-type memory effects
Solution Approach 1:
The control system dynamically adapts to the power amplifier's characteristics by continuously monitoring the output signal and adjusting control parameters in real-time. This dynamic approach allows the system to effectively control amplifiers with hysteresis-type memory effects, which have time-dependent behavior that cannot be handled by static predistortion tables
Solution Approach 2:
The system changes control parameters (gain and phase) based on the actual measured output signal characteristics rather than relying on pre-stored lookup tables. This allows the system to adapt to different amplifier types and operating conditions, including those with memory effects, by continuously optimizing control parameters
3Ease of operation
If lookup table approach is used to store predistortion values, then gain and phase adjustments can be made, but the system complexity increases with calibration procedures
Solution Approach 1:
The control system eliminates the need for external calibration equipment and procedures by performing self-adjustment through internal measurement and feedback. The system automatically determines the appropriate gain and phase corrections by monitoring its own output performance, simplifying the overall system architecture while maintaining ease of operation
Data Source
AI summary
An apparatus for controlling the gain and phase of an input signal input to a power amplifier comprises a gain control loop configured to control the gain of the input signal based on power levels of the input signal and an amplified signal output by the power amplifier, to obtain a predetermined gain of the amplified signal, and a phase control loop configured to obtain an error signal related to a phase difference between a first signal derived from the input and a second signal derived from the amplified signal, and control the phase based on the error signal, to obtain a predetermined phase of the amplified signal. The phase control loop delays the first signal such that the delayed first signal and the second signal used to obtain the error signal correspond to the same part of the input signal. The apparatus may be included in a satellite.