Two-Stage Digital Pre-Distortion for PA Signal Linearity
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Solution Overview
Problem
Wireless communication systems face challenges with signal distortion due to non-linear power amplifiers, leading to interference and degradation of bit-error rate and data throughput, which existing methods like power back-off reduce efficiency.
Innovation Solution
Implementing digital pre-distortion (DPD) and digital post-distortion (DPoD) techniques, including frequency-selective DPD, to mitigate in-band and out-of-band distortions dynamically, using assistance information for accurate modeling and iterative compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If power back-off is used to reduce distortion from non-linear power amplifiers, then signal distortion is reduced, but transmission power efficiency deteriorates
Solution Approach 1:
The patent applies preliminary anti-action by implementing digital pre-distortion (DPD) that anticipates and counteracts the non-linear distortion effects of the power amplifier before the signal is amplified. The DPD circuit pre-modifies the input signal with inverse distortion characteristics, so that when the signal passes through the non-linear PA, the pre-applied correction compensates for the expected non-linear effects, achieving distortion reduction without requiring power back-off
Solution Approach 2:
The patent implements preliminary action by performing digital signal processing and distortion compensation in advance of the power amplification stage. The DPD circuit calculates and applies correction factors based on pre-stored PA characteristic models, preparing the signal with anticipated corrections before it enters the non-linear amplifier, thereby preventing distortion rather than correcting it afterward
2Object-affected harmful factors
If digital pre-distortion is applied to mitigate signal distortion, then signal quality is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the DPD function into multiple independent circuits: a first DPD circuit that processes the input signal and applies initial distortion compensation, and a second DPD circuit that receives the output of the first DPD circuit and applies additional distortion compensation. This segmented architecture allows each circuit to handle specific aspects of distortion correction, making the overall complex DPD system more manageable and implementable
Solution Approach 2:
The patent introduces an intermediary element by inserting the first DPD circuit between the signal source and the power amplifier, and the second DPD circuit between the first DPD circuit and the PA. These intermediary DPD circuits act as mediators that progressively refine the signal, applying distortion compensation in stages rather than requiring a single complex correction stage directly at the PA input
Data Source
AI summary
Certain aspects of the present disclosure provide techniques for digital pre-distortion (DPD). An apparatus for wireless communication generally includes a power amplifier (PA); a first DPD circuit, a second DPD circuit, and a transmitter. The first DPD circuit is generally configured to: obtain an input signal; apply a first DPD to the input signal to generate a first resulting signal; and output the first resulting signal to the second DPD circuit. The second DPD circuit is generally configured to: obtain the first resulting signal from the first DPD circuit; apply a second DPD to the first resulting signal to generate a second resulting signal; and output the second resulting signal to the PA. The PA is generally configured to amplify the second resulting signal to generate an amplified second resulting signal. The transmitter is generally configured to transmit the amplified second resulting signal to a second apparatus.