VRF Equalizer Circuit for Load-Modulation Ripple in ETICs
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Solution Overview
Problem
Envelope tracking for Doherty power amplifiers results in non-linear currents and undesirable ripples due to load modulation, which affects the efficiency and performance of wireless communication devices.
Innovation Solution
A virtual radio frequency (VRF) equalizer is introduced in the envelope tracking integrated circuit (ETIC) to cancel ripple caused by load modulation, using circuitry that includes a first transform function and additional compensation elements to improve the performance and efficiency of the Doherty power amplifier stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking is applied to Doherty power amplifiers to improve efficiency, then power efficiency is improved, but load modulation causes non-linear currents and undesirable ripples that degrade signal quality
Solution Approach 1:
The patent converts the harmful ripple effects of load modulation into a beneficial solution by measuring the ripple characteristics and generating an equalizing signal that counteracts them. The VRF equalizer uses the same load modulation mechanism that causes ripples to create compensating signals, transforming the harmful effect into a useful correction mechanism that maintains both efficiency and signal quality.
Solution Approach 2:
The patent introduces a virtual radio frequency (VRF) equalizer as an intermediary component between the envelope tracking circuit and the power amplifier. This equalizer includes a ripple measurement path and a compensation path that processes signals through transform functions to generate corrective signals, acting as a mediator that eliminates ripples while preserving the efficiency benefits of envelope tracking.
2Use of energy by moving object
If load modulation is used in envelope tracking to control power amplifier operation, then efficiency is improved, but signal distortion increases due to non-linear currents
Solution Approach 1:
The patent implements a feedback mechanism where the VRF equalizer continuously measures the ripple and non-linear current characteristics produced by load modulation. The measured signals are processed through transform functions to generate compensating feedback signals that are applied to correct the distortion, creating a closed-loop system that maintains signal quality while preserving efficiency improvements.
Solution Approach 2:
The VRF equalizer serves as an intermediary processing stage that receives the modulated signal, separates the useful envelope information from the harmful non-linear components, and reconstructs the signal with corrected characteristics. This intermediary function preserves the efficiency benefits of load modulation while eliminating signal quality degradation.
3Use of energy by moving object
If envelope tracking circuitry is added to control power amplifier efficiency, then energy efficiency is improved, but device complexity increases
Solution Approach 1:
The VRF equalizer is designed to perform multiple functions within a single integrated circuit: it measures ripple characteristics, generates equalizing signals, and compensates for non-linear effects. By combining these functions into one multi-functional block, the patent reduces overall device complexity compared to using separate circuits for each function while still achieving the efficiency improvements of envelope tracking.
Solution Approach 2:
The envelope tracking system with VRF equalizer is designed to be self-regulating, where the equalizer automatically measures and corrects its own ripple effects without requiring external intervention. The circuit uses its own output signals to generate correction signals, making the system self-sufficient and reducing the need for additional external components or complex control systems.
Data Source
AI summary
A virtual radio frequency (VRF) equalizer for an envelope tracking integrated circuit (ETIC) is disclosed. In one aspect, an ETIC provides envelope tracking (ET) for a barely Doherty (BD) power amplifier stage. The VRF equalizer includes circuitry that provides ripple cancelation that is caused by load modulation of the BD power amplifier stage. Additional circuitry is included to compensate for an amplifier within the ETIC. By canceling the ripple within the ETIC, the overall performance and efficiency of the BD power amplifier stage is improved, resulting in better performance of a transmitter in a wireless communication device.