Envelope Tracking Amplifier Voltage Pre-Distortion for Linearity
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Solution Overview
Problem
Envelope tracking (ET) amplifier circuits in mobile communication devices experience degraded linearity performance due to deviations in ET modulated voltage caused by impedance variations, particularly at higher modulation bandwidths, leading to increased power consumption and thermal dissipation.
Innovation Solution
A voltage memory digital pre-distortion (mDPD) circuit is employed to digitally pre-distort target voltage amplitudes based on the time-variant signal envelope, ensuring that the ET modulated voltage closely tracks the target voltage amplitudes, thereby mitigating deviations and improving linearity performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking is used to improve power amplifier efficiency, then power consumption and thermal dissipation are reduced, but linearity performance degrades due to ET modulated voltage deviation
Solution Approach 1:
The voltage mDPD circuit performs preliminary digital pre-distortion on the target voltage amplitudes based on the time-variant signal envelope to anticipate and compensate for impedance variations before they affect the ET modulated voltage, thereby maintaining linearity performance while using envelope tracking for power efficiency
Solution Approach 2:
The system uses feedback from the signal envelope information to continuously adjust and pre-distort the target voltage amplitudes, creating a closed-loop control mechanism that maintains accurate voltage tracking despite impedance variations in the envelope tracking circuit
2Productivity
If modulation bandwidth is increased to achieve higher data rates, then wireless communication performance is improved, but ET modulated voltage deviation increases causing linearity degradation
Solution Approach 1:
The voltage mDPD circuit applies pre-distortion to the target voltage amplitudes before they are applied to the power amplifier, anticipating the effects of high modulation bandwidth on voltage tracking accuracy and compensating in advance to maintain linearity at higher data rates
Data Source
AI summary
An envelope tracking (ET) amplifier circuit is provided. In examples discussed herein, an amplifier circuit(s) is configured to amplify a radio frequency (RF) signal based on an ET modulated voltage. A tracker circuit is configured to generate the ET modulated voltage based on a number of target voltage amplitudes derived from a time-variant signal envelope of the RF signal. However, the tracker circuit can cause the ET modulated voltage to deviate from the target voltage amplitudes due to various impedance variations. In this regard, a voltage memory digital pre-distortion (mDPD) circuit digitally pre-distorts the target voltage amplitudes based on the time-variant signal envelope such that the ET modulated voltage can closely track the target voltage amplitudes. As such, it is possible to mitigate ET modulated voltage deviation, thus helping to improve overall linearity performance of the ET amplifier circuit.