DPD Feedback Control for Power Amplifier Linearity in Wireless Transmission
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Solution Overview
Problem
Nonlinear characteristics of power amplifiers in wireless communication systems cause distortion, leading to increased bit error rates, decreased data transmission rates, and spectral interference, particularly in OFDM and OFDMA techniques.
Innovation Solution
A device with a transmission path including a DPD conversion module and a power amplifier, coupled with a feedback path to generate a feedback signal, where the DPD control module adjusts the pre-distortion processing strategy based on amplitude and phase differences between the transmission and feedback signals, counteracting nonlinear characteristics for improved linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power amplifiers are used to amplify transmission signal power, then transmission power is increased, but nonlinear distortion is introduced causing bit error rate increase and spectral interference
Solution Approach 1:
The DPD conversion module performs pre-distortion processing on the transmission signal before amplification by the power amplifier. By applying inverse nonlinear characteristics in advance to the signal, the distortion introduced by the power amplifier is compensated, thereby reducing bit error rate while maintaining high transmission power
Solution Approach 2:
The feedback path extracts a portion of the amplified transmission signal and feeds it back to the DPD control module. The control module compares the original signal with the amplified signal to detect distortion characteristics and dynamically adjusts the pre-distortion parameters, creating a closed-loop system that continuously optimizes distortion compensation
2Power
If power amplifiers are used to amplify transmission signal power, then transmission power is increased, but spectral interference and out-of-band spurs increase
Solution Approach 1:
The DPD conversion module applies pre-distortion processing before power amplification to linearize the amplifier's output characteristics. This preliminary correction prevents the generation of spectral regrowth and out-of-band spurs that would otherwise occur during high-power amplification
Solution Approach 2:
The feedback mechanism continuously monitors the amplified signal for spectral distortion and adjusts the pre-distortion parameters accordingly, minimizing out-of-band emissions and spectral interference while maintaining high transmission power
3Reliability
If pre-distortion processing is applied to counteract nonlinear characteristics, then linearity is improved, but device complexity increases
Solution Approach 1:
The DPD conversion module serves as an intermediary component between the signal source and the power amplifier. It introduces controlled nonlinear processing that compensates for the amplifier's nonlinearities, improving overall linearity while adding only moderate complexity through dedicated preprocessing circuitry
Solution Approach 2:
The feedback loop provides automatic adaptation of pre-distortion parameters based on actual amplifier performance, eliminating the need for complex manual calibration and enabling the system to maintain optimal linearity across varying operating conditions with relatively simple control logic
Data Source
AI summary
In certain aspects, a device for wireless transmission includes a transmission path, a feedback path, and a DPD control module. The transmission path includes a digital pre-distortion (DPD) conversion module configured to perform pre-distortion processing on an amplitude and a phase of a transmission signal based on a pre-distortion processing strategy. The transmission path further includes a power amplifier coupled to a downstream of the DPD conversion module and configured to amplify a power of the transmission signal. The feedback path is coupled to the transmission path at the downstream of the power amplifier and configured to generate a feedback signal. The DPD control module is coupled to the feedback path and the DPD conversion module and configured to adjust the pre-distortion processing strategy based on an amplitude difference and a phase difference between the transmission signal and the feedback signal.