Envelope-Tracking RF Power Amplifier for Wideband Linearity
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Solution Overview
Problem
Power amplifiers for wireless communication devices face challenges in achieving high power efficiency and accurate signal restoration, particularly when operating with wide bandwidth RF signals, due to limitations in voltage and switching rate of driver and switching amplifiers, and inefficiencies at low output power levels.
Innovation Solution
A power amplifier design that decomposes the amplitude-modulated component into two control signals, mixes one with the phase-modulated component, and amplifies the other control signal to amplitude-modulate the RF signal, ensuring high power efficiency and accurate signal restoration by reducing the dynamic range of the control signals and using these signals to modulate the RF amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a power amplifier is operated in a high backoff state to improve linearity, then signal distortion requirements are met, but power efficiency is lowered
Solution Approach 1:
The input signal is segmented into amplitude component signal and phase component signal. The amplitude component is extracted and used to control the output power supply voltage of the RF amplifier, while the phase component is amplified by the RF amplifier. This segmentation allows the amplifier to operate efficiently while maintaining linearity through envelope tracking.
Solution Approach 2:
The output power supply voltage of the RF amplifier is dynamically changed based on the amplitude component signal. By tracking the envelope of the input signal and adjusting the supply voltage accordingly, the amplifier maintains high efficiency across varying output power levels while preserving signal linearity.
2Use of energy by moving object
If the dynamic range of control signals is reduced to improve power efficiency, then average output voltage is maintained, but signal accuracy may be compromised
Solution Approach 1:
The control mechanism is moved to the power supply voltage dimension rather than directly controlling the amplifier input. By modulating the output power supply voltage according to the amplitude component, the system achieves efficient power utilization while maintaining signal fidelity through a different control dimension.
Solution Approach 2:
The amplitude component signal serves as an intermediary between the input signal and the power supply control mechanism. It translates the envelope information into power supply modulation, enabling efficient amplification without directly distorting the phase component signal.
3Use of energy by moving object
If driver amplifier and switching amplifier are used to amplify amplitude component signal, then power efficiency is improved, but voltage and switching rate limitations restrict wide bandwidth operation
Solution Approach 1:
The amplitude component signal is extracted and processed separately from the phase component signal. This extraction allows the amplitude information to be used for power supply control without requiring the driver and switching amplifiers to handle the full bandwidth signal, thereby overcoming their speed limitations while maintaining power efficiency benefits.
Data Source
AI summary
A power amplifier based on EER technology or ET technology extracts an amplitude-modulated component from a modulated signal as an input signal which includes the amplitude-modulated component and a phase-modulated component, and decomposes the amplitude-modulated component into two control signals whose product is proportional to the amplitude-modulated component. One of the control signals is amplified by a highly efficient amplifier, and thereafter is used to amplitude-modulate an output from an RF amplifier. The other control signal is converted by a pulse modulator into a rectangular-wave signal, which is then mixed with the phase-modulated component or the modulated signal and input to the RF amplifier.