Envelope Tracking PA Predistortion for RF Linearity
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Solution Overview
Problem
Mobile communication devices face increased power consumption and thermal dissipation due to higher output power requirements for RF signals, leading to performance compromises, and envelope tracking technologies introduce phase and amplitude distortions that worsen these issues.
Innovation Solution
The integration of predistortion circuits, including isogain and phase modulation predistortion, within an envelope tracking integrated circuit to correct for amplitude and phase distortions in power amplifiers, ensuring more linear gain and preserving the benefits of envelope tracking in millimeter wave transmitters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking is used to improve PA efficiency and reduce power consumption, then power consumption and thermal dissipation are reduced, but phase and amplitude distortions increase
Solution Approach 1:
The predistortion circuits apply corrective phase and amplitude adjustments to the RF signal before it reaches the power amplifier. By pre-compensating for the expected nonlinear distortions that will be introduced by envelope tracking, the system maintains signal linearity while benefiting from reduced power consumption and thermal dissipation.
2Productivity
If output power of RF signals is increased to achieve higher data rates, then data rates are improved, but power consumption and thermal dissipation increase
Solution Approach 1:
The system dynamically adjusts the supply voltage to the power amplifier using envelope tracking, which modulates the voltage according to the instantaneous signal envelope. This allows the amplifier to operate at higher efficiency across varying power levels, enabling high data rates while reducing overall power consumption and thermal dissipation compared to traditional fixed-voltage operation.
3Power
If multiple PAs are used to increase output power, then output power is improved, but phase and amplitude distortions increase
Solution Approach 1:
The system divides the high-power transmission task across multiple parallel power amplifiers. Each PA handles a portion of the total output power, and individual predistortion circuits compensate for distortions in each amplifier path. This segmentation approach maintains signal linearity while achieving the required high output power through parallel operation.
Data Source
AI summary
An envelope tracking (ET) power amplifier apparatus with predistortion includes an amplifier circuit configured to amplify a radio frequency (RF) signal based on an ET voltage and a tracker circuit configured to generate the ET voltage based on an ET target voltage. The amplifier circuit may introduce phase and amplitude distortions to the signal being amplified. To offset such distortions, exemplary aspects of the present disclosure add an isogain predistortion circuit in an ET integrated circuit (IC) to correct for amplitude distortions and add a phase modulation predistortion circuit to correct for phase distortions.