Envelope Tracking Amplifier Feedback for Wideband RF Linearity
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Solution Overview
Problem
Envelope tracking (ET) power amplifiers in mobile communication devices face challenges in maintaining linearity and efficiency, particularly at high modulation bandwidths, due to distortions caused by trace inductance, leading to unwanted amplitude clipping in RF signals.
Innovation Solution
The ET amplifier apparatus incorporates a distributed ET integrated circuit (DETIC) and an ET integrated circuit (ETIC) that dynamically adjusts a low-frequency current and distributed voltage based on feedback signals to maintain efficiency across a wider range of modulation bandwidths, minimizing distortion and size/cost impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the time-variant ET voltage is generated to track the time-variant power envelope with a high modulation bandwidth, then the power amplifier efficiency is improved, but the voltage becomes susceptible to distortions caused by trace inductance, leading to amplitude clipping in the RF signal
Solution Approach 1:
The patent implements a feedback mechanism where the distorted ET voltage is detected and fed back to a control circuit. The control circuit processes this feedback signal and adjusts the ET voltage generation accordingly, creating a closed-loop system that automatically compensates for distortions caused by trace inductance, thereby maintaining signal linearity while preserving power amplifier efficiency
Solution Approach 2:
The patent introduces an intermediary control circuit between the ET voltage source and the power amplifier. This control circuit acts as a mediator that processes the ET voltage signal, compensates for distortions, and delivers a corrected voltage to the amplifier, thereby isolating the system from the harmful effects of trace inductance while maintaining high-frequency tracking capability
2Device complexity
If a traditional ET amplifier design is used, then the circuit complexity is reduced, but the ability to maintain consistent linearity across wide modulation bandwidth ranges is compromised
Solution Approach 1:
The patent implements dynamic adjustment mechanisms where the ET voltage and bias conditions are continuously adapted based on real-time signal characteristics and distortion feedback. This dynamic behavior enables the amplifier to maintain optimal linearity across varying modulation bandwidths without requiring multiple fixed designs, achieving bandwidth adaptability through continuous optimization rather than static configuration
3Reliability
If the trace inductance is minimized to reduce distortion, then the signal quality is improved, but the physical size of the amplifier apparatus increases
Solution Approach 1:
The control circuit serves as an intermediary that electronically compensates for the effects of trace inductance, allowing the use of compact PCB layouts with inherent inductance while maintaining signal quality. This electronic compensation approach avoids the need for physically larger low-inductance designs, achieving signal quality improvement without increasing amplifier size
Data Source
AI summary
An envelope tracking (ET) amplifier apparatus is provided. The ET amplifier apparatus includes an ET integrated circuit (IC) (ETIC) and a distributed ETIC (DETIC) coupled to the ETIC. The DETIC may be configured to provide a distributed voltage to a distributed amplifier circuit for amplifying a distributed radio frequency (RF) signal. In examples discussed herein, the ETIC is configured to generate a low-frequency current, which can affect the distributed voltage, at a desired level based on a feedback signal received from the DETIC. The DETIC may be configured to generate the feedback signal based on an indication(s) related to the distributed voltage. By dynamically adjusting the low-frequency current, and thus the distributed voltage, based on the feedback signal, it may be possible to maintain operating efficiency of the distributed amplifier circuit across a wider range of modulation bandwidth with minimal cost and/or size impact on the ET amplifier apparatus.