Dual-Input Voltage mDPD Circuit for Accurate Envelope Tracking
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Solution Overview
Problem
Envelope tracking (ET) systems in wireless communication devices experience deviations in voltage amplitudes due to impedance variations and nonlinearities, particularly at higher modulation bandwidths, leading to degraded linearity and efficiency in power amplifiers.
Innovation Solution
A dual-input voltage memory digital pre-distortion (mDPD) circuit is introduced to digitally pre-distort target voltage amplitudes based on signal amplitudes, ensuring the ET voltage closely tracks the target voltage amplitudes, thereby mitigating deviations and improving overall 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 voltage amplitude deviations occur due to impedance variations and nonlinearities
Solution Approach 1:
The patent applies preliminary action by implementing a digital pre-distortion circuit that pre-compensates voltage amplitude deviations before they occur in the envelope tracking system. The circuit calculates compensation values based on predicted impedance variations and applies them in advance to the control signal, preventing the deviations from manifesting in the final output. This resolves the contradiction by maintaining voltage amplitude accuracy without sacrificing power efficiency.
Solution Approach 2:
The patent implements feedback mechanisms where the actual voltage amplitudes are monitored and compared against target values. The deviation information is fed back to the digital pre-distortion circuit, which adjusts compensation parameters in real-time. This closed-loop feedback system continuously corrects for impedance variations and nonlinearities, ensuring reliable voltage amplitude tracking while maintaining the power efficiency benefits of envelope tracking.
2Use of energy by moving object
If tracker circuit adjusts supply voltage to maintain higher efficiency, then power consumption is reduced, but linearity performance degrades due to voltage deviations
Solution Approach 1:
The digital pre-distortion circuit performs preliminary compensation by calculating and applying correction factors to the envelope signal before it reaches the tracker circuit. This pre-action accounts for known nonlinearities and impedance effects, ensuring that the tracker circuit operates with corrected reference values. As a result, the supply voltage adjustments maintain both high efficiency and improved linearity performance.
Solution Approach 2:
The patent changes parameters by dynamically adjusting compensation factors in the digital pre-distortion circuit based on operating conditions. The circuit modifies gain, phase, and amplitude parameters of the pre-compensated signal to optimize both efficiency and linearity across different power levels and modulation bandwidths. This parameter adaptation resolves the contradiction by allowing the system to maintain high efficiency while achieving better linearity through intelligent parameter control.
3Manufacturing precision
If digital pre-distortion is applied to correct voltage deviations, then linearity performance is improved, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary digital pre-distortion circuit that acts as a mediator between the envelope signal source and the tracker circuit. This intermediary component performs the complex compensation calculations in the digital domain, where flexibility and precision are easier to achieve, rather than requiring complex analog circuitry. The digital intermediary resolves the contradiction by providing linearity improvement through software-based processing rather than complex hardware modifications.
Solution Approach 2:
The patent substitutes mechanical/analog compensation methods with digital signal processing. Instead of using complex analog circuits with multiple variable components to achieve pre-distortion, the system uses digital algorithms implemented in firmware or software. This substitution dramatically reduces device complexity while maintaining or improving linearity performance, as digital systems offer greater precision with fewer physical components.
Data Source
AI summary
A dual-input voltage memory digital pre-distortion (mDPD) circuit and related ET apparatus are provided. In examples discussed herein, an ET apparatus includes an amplifier circuit(s) configured to amplify a radio frequency (RF) signal based on an ET voltage. A tracker circuit is configured to generate the ET voltage based on a number of target voltage amplitudes derived from a number of signal amplitudes of the RF signal. However, the tracker circuit can cause the ET voltage to deviate from the target voltage amplitudes due to various inherent impedance variations, particularly at a higher modulation bandwidth. In this regard, a dual-input voltage mDPD circuit is configured to digitally pre-distort the target voltage amplitudes based on the signal amplitudes such that the ET voltage can closely track the target voltage amplitudes. As such, it is possible to mitigate ET voltage deviation, thus helping to improve overall linearity performance of the ET apparatus.