Baseband Predistortion for Power Amplifier Linearization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power amplifiers in communication systems face challenges in achieving simultaneous power and bandwidth efficiency due to their nonlinear characteristics, and existing linearization techniques are costly and complex to implement.
Innovation Solution
A system and method that uses a baseband predistorter with a linear-phase prefilter to compensate for the nonlinearity of power amplifiers, employing a semi-analytical method to characterize the amplifier's response curve and generate predistortion coefficients, which reduces out-of-band spectral regrowth and improves transmitter linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If linear amplification is used to preserve signal shape, then bandwidth efficiency is improved, but power efficiency deteriorates
Solution Approach 1:
The patent applies predistortion technique where a predistorter is placed before the power amplifier to pre-compensate for its nonlinear characteristics. The predistorter modifies the input signal in advance so that after passing through the nonlinear PA, the overall transmission characteristic becomes linear, thus preserving signal shape while enabling the PA to operate at higher efficiency levels
2Reliability
If power amplifier operates at small input signal for linear amplification, then signal shape is preserved, but power efficiency deteriorates
Solution Approach 1:
The predistorter pre-modifies the input signal to counteract the expected nonlinear distortion of the power amplifier. This allows the PA to operate in its high-efficiency nonlinear region while the predistorted signal ensures that the final output remains linear and preserves the original signal shape
Solution Approach 2:
The patent employs feedback mechanisms to measure the actual output of the power amplifier and use this information to adjust the predistortion coefficients. This closed-loop approach ensures that the predistortion accurately compensates for PA nonlinearities, maintaining linearity while operating at optimal power efficiency points
3Reliability
If Cartesian feedback technique is used for linearization, then nonlinearity suppression is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the complex Cartesian feedback system with a more economical predistortion approach that uses simpler computational algorithms and requires minimal or no large memory tables. The predistorter can be implemented using efficient mathematical models that compute correction factors in real-time without requiring extensive lookup tables, thus reducing both hardware complexity and cost while maintaining effective nonlinearity suppression
Data Source
AI summary
A method and system are provided to compensate for the nonlinearity of a wireless transmitter. The method includes sending a predetermined input bit stream to the power amplifier, calculating the coefficients of the polynomial representing the response curve of the power amplifier and generating the predistortion coefficients of the polynomial representing the response curve of the predistortor. The method linearizes the response curve of the transmitter chain in a communication device.