Adaptive RF Power Amplifier Pre-Distortion for Load Mismatch
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Solution Overview
Problem
Radio frequency power amplifiers (RFPA) face performance impairment due to load mismatch, leading to reduced efficiency and linearity, which is typically addressed by power backoff, resulting in lower power delivery.
Innovation Solution
An adaptive pre-distortion system that includes a distortion characterization circuit and a distortion circuit to digitally pre-distort signals based on measured amplifier distortion, using closed-loop feedback to dynamically adjust pre-distortion values for amplitude and phase, thereby compensating for distortion and improving RFPA performance across varying load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed power backoff is applied to improve linearity under load mismatch, then distortion is reduced, but delivered power and efficiency decrease
Solution Approach 1:
The patent implements dynamic pre-distortion adjustment by continuously monitoring output signal characteristics and adapting the pre-distortion parameters in real-time. This allows the system to optimize linearity for current operating conditions without permanently reducing power delivery, unlike fixed power backoff which statically limits power output.
Solution Approach 2:
The system employs feedback mechanisms where the output signal from the power amplifier is monitored and used to adjust pre-distortion parameters. This closed-loop approach enables the system to maintain linearity by compensating for actual distortion occurring under current load conditions, rather than applying conservative fixed power reduction.
Solution Approach 3:
The patent applies pre-distortion to the input signal before it reaches the power amplifier, anticipating and compensating for expected distortion. This preliminary correction allows the amplifier to operate at higher power levels while still achieving linearity, as the distortion is pre-compensated rather than corrected after the fact.
2Reliability
If fixed power backoff is used to ensure linear operation, then distortion is reduced, but efficiency is lost
Solution Approach 1:
The system dynamically adjusts pre-distortion parameters based on real-time monitoring of amplifier output characteristics. This allows the amplifier to operate efficiently at higher power levels by adapting linearity compensation to actual operating conditions, rather than maintaining conservative fixed power backoff that reduces efficiency.
Solution Approach 2:
The patent changes pre-distortion parameters dynamically based on operating conditions such as load impedance variations and temperature. By adjusting these parameters in real-time, the system maintains linearity and efficiency across varying conditions, rather than using fixed parameters that optimize for worst-case scenarios only.
3Power
If adaptive pre-distortion is implemented to maximize delivered power, then efficiency is improved, but system complexity increases
Solution Approach 1:
The patent replaces complex hardware-based distortion compensation mechanisms with digital signal processing approaches. By using digital pre-distortion algorithms and software-based adaptation, the system achieves adaptive linearity compensation without requiring complex analog circuitry, thereby managing system complexity while maximizing power delivery.
Solution Approach 2:
The system integrates multiple functions into the pre-distortion processor, including distortion measurement, parameter adaptation, and signal compensation. This multi-functional approach consolidates what could be separate complex subsystems into a single integrated unit, reducing overall system complexity while maintaining adaptive power maximization capabilities.
4Reliability
If pre-distortion is adjusted for each packet to account for environmental variations, then linearity is maintained, but processing time and complexity increase
Solution Approach 1:
The system performs pre-distortion parameter adjustment in advance for each packet transmission. By measuring distortion characteristics and configuring pre-distortion parameters before the actual data transmission, the system ensures linearity is maintained without adding significant delay to the communication process, as the adaptation occurs during packet preparation rather than during transmission.
Data Source
AI summary
In an embodiment, an apparatus includes: a modulator to modulate a first signal; a distortion circuit coupled to the modulator to digitally pre-distort the first signal to compensate for a distortion of an amplifier; a distortion characterization circuit coupled to the distortion circuit to determine the distortion of the amplifier and configure the distortion circuit based on the determined distortion; a mixer coupled to the distortion circuit to upconvert the pre-distorted first signal to a pre-distorted radio frequency (RF) signal; and the amplifier coupled to the mixer to amplify the pre-distorted RF signal and output an amplified RF signal.