Multi-rate Crest Factor Reduction for RFPA Linearity
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Solution Overview
Problem
High crest factor signals distort the linearity of power amplifiers in transmitters, leading to inefficiencies and reduced performance in wireless communication systems, particularly in carrier aggregation scenarios where peak-to-average power ratio (PAPR) increases with the number of carriers, degrading radio frequency power amplifier (RFPA) efficiency and linearity.
Innovation Solution
The implementation of a multi-rate crest factor reduction (CFR) method that involves receiving input signals at a first sampling rate, performing peak detection, downsampling, generating windowing input samples, upsampling, and generating peak reduction samples to produce an output signal with reduced crest factor, thereby improving the linearity and efficiency of RFPA by reducing PAPR through windowing and digital predistortion (DPD) co-operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carrier aggregation is used to increase data rate, then throughput is improved, but PAPR increases causing RFPA linearity degradation
Solution Approach 1:
The patent applies digital predistortion (DPD) to the signal before it enters the power amplifier. By pre-calculating and applying inverse distortion characteristics to the signal, the system compensates for upcoming nonlinearities in the RFPA, maintaining linearity while allowing high PAPR signals to pass through without degrading amplifier performance.
Solution Approach 2:
The patent dynamically adjusts the crest factor reduction parameters based on the number of active carriers and signal characteristics. By changing the reduction amount and processing parameters according to the actual signal conditions, the system maintains optimal RFPA linearity across varying data rates and carrier configurations.
2Reliability
If crest factor reduction is applied to improve RFPA linearity, then power amplifier efficiency is improved, but signal processing complexity increases
Solution Approach 1:
The patent divides the crest factor reduction process into multiple stages: initial peak detection, selective windowing application, and digital predistortion. By segmenting the processing into distinct functional blocks that can be independently optimized and implemented, the system reduces overall processing complexity while maintaining effective linearity improvement.
Solution Approach 2:
The patent introduces a windowing function as an intermediary element between the input signal and the power amplifier. This windowing function selectively attenuates peak portions of the signal, acting as a mediator that protects the RFPA from high PAPR effects without requiring complex real-time distortion correction throughout the entire signal path.
3Productivity
If multi-rate processing is used to reduce crest factor, then processing efficiency is improved, but implementation complexity increases
Solution Approach 1:
The patent implements dynamic rate conversion where the processing rate is adjusted based on the number of active carriers and signal conditions. The system can operate at different processing rates (e.g., 1x, 2x, 4x) depending on the carrier configuration, allowing optimal processing efficiency for each scenario while managing implementation complexity through adaptive rather than fixed-rate processing.
Data Source
AI summary
A computer-implemented method for reducing crest factor by an electronic device includes: receiving a plurality of first samples of a first input signal. The plurality of first samples are generated at a first sampling rate. A first peak detection is performed based on the plurality of first samples to generate a plurality of first peak detection output samples. A plurality of first windowing input samples are generated at a second sampling rate by downsampling the plurality of first peak detection output samples. A plurality of first windowing output samples are generated based on the plurality of first windowing input samples. A plurality of first peak reduction samples are generated at the first sampling rate by upsampling the plurality of first windowing output samples. A first output signal is generated based on the plurality of first samples and the plurality of first peak reduction samples.