Power Amplifier Gain and Phase Control for GaN Hysteresis
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Solution Overview
Problem
Conventional power amplifier control systems require lengthy calibration procedures and are ineffective for amplifiers with hysteresis-type memory effects, such as Gallium Nitride (GaN) amplifiers, which affect gain and phase linearity.
Innovation Solution
A control system using separate gain and phase control loops that monitor both input and output signals to apply real-time adjustments, eliminating the need for calibration and effectively managing hysteresis-type memory effects by using a feed-forward control loop for phase adjustments and a differential amplifier for gain control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If open-loop control with lookup table is used, then gain and phase predistortion can be applied, but calibration time becomes excessively long (up to 48 hours)
Solution Approach 1:
The patent implements a feedback mechanism where the output signal is sampled and fed back to an error detector that compares it with the input signal. The error signal generated is used to adjust the predistortion coefficients in real-time, eliminating the need for lengthy open-loop calibration procedures while maintaining gain and phase linearity.
Solution Approach 2:
The control system performs self-calibration by automatically detecting errors between input and output signals and adjusting its own predistortion parameters without external intervention. This self-service capability reduces calibration time from 48 hours to minimal operational adjustment time.
2Reliability
If conventional open-loop control is used, then predistortion can be applied, but the system is ineffective for amplifiers with hysteresis-type memory effects
Solution Approach 1:
The feedback loop continuously monitors the actual output and adjusts predistortion parameters in real-time, enabling the system to compensate for hysteresis-type memory effects that cannot be addressed by static open-loop predistortion. This makes the system effective for GaN and other memory-effect amplifiers.
Solution Approach 2:
The control system transitions from static predistortion coefficients to dynamic, adaptive coefficients that change in real-time based on the amplifier's actual performance. This dynamic adjustment capability allows the system to track and compensate for time-varying memory effects.
3Speed
If separate gain and phase control loops are implemented, then real-time adjustments can be made, but system complexity increases
Solution Approach 1:
The control system is segmented into separate gain control and phase control loops, each independently adjusting its parameter. This segmentation enables parallel processing and faster response times while keeping each individual loop relatively simple and manageable.
Solution Approach 2:
While maintaining separate control loops for gain and phase, the system merges their operations through a unified feedback mechanism that coordinates both adjustments simultaneously, achieving fast real-time control without excessive overall system complexity.
Data Source
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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 is arranged to delay the first signal before obtaining the error 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 gain control loop may compare a power of a third signal derived from the input signal and a power of a fourth signal derived from the amplified signal. The third and fourth signals may be output by first and second couplers, which may have coupling factors that are selected such that the third and fourth signals have the same power level when the amplified signal has the predetermined gain. The current gain and phase of the amplified signal may be dependent on an operational history of the power amplifier, which may be a GaN power amplifier, and the apparatus and power amplifier may be included in a satellite. In another embodiment, a satellite includes a power amplifier control system that uses a feed-forward control loop to control both the gain and phase of a signal input to the power amplifier.