External DPD Coefficient Calibration for PA Nonlinearity Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Power amplifiers in communication systems experience distortion when operated near their maximum power or saturation point, leading to reduced signal quality, especially for higher order modulations. Addressing this distortion within the transmit system adds complexity and cost.
Innovation Solution
An external digital pre-distorter coefficient computation method is implemented to compensate for power amplifier nonlinearity. This involves receiving a defined waveform, capturing output samples, calculating a PA model, determining digital pre-distorter (DPD) coefficients for various power levels, frequencies, and temperatures, and storing these coefficients for predistorting input waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power amplifier is operated close to maximum power or saturation point to increase output power, then the power output is improved, but signal distortion increases due to nonlinear characteristics
Solution Approach 1:
The patent applies digital predistortion by pre-modifying the input signal to compensate for anticipated nonlinear distortion in the power amplifier. The DPD coefficients are calculated in advance based on PA characteristics and stored for later use, allowing the system to operate the PA near saturation while maintaining signal quality through pre-applied correction.
2Manufacturing precision
If digital pre-distortion is implemented within the transmit system to compensate for distortion, then signal quality is improved, but system complexity and cost increase
Solution Approach 1:
The patent extracts the complex DPD coefficient calculation function from the transmit system and relocates it to an external calibration system. The calibration system performs the computationally intensive PA modeling and DPD coefficient determination offline, then provides the coefficients to the transmit system which only needs to store and apply them, significantly reducing transmit system complexity.
Solution Approach 2:
The patent introduces an external calibration system as an intermediary between the PA characterization and the transmit system operation. This calibration system acts as a mediator that captures PA output samples, calculates the PA model, and determines DPD coefficients without being permanently integrated into the transmit signal path, simplifying the main transmit system architecture.
3Measurement precision
If DPD coefficients are calculated for multiple power levels, frequencies, and temperatures, then compensation accuracy is improved, but computation time and processing requirements increase
Solution Approach 1:
The patent performs comprehensive DPD coefficient calculations for multiple power levels, frequencies, and temperature conditions in advance during an offline calibration phase. The external calibration system captures PA samples and computes the PA model and DPD coefficients beforehand, storing them for later retrieval and application, thus avoiding time-consuming real-time calculations during normal transmit operation.
Data Source
AI summary
Digital pre-distorter (DPD) coefficients can be used to compensate for non-linearity of a power amplifier (PA). A system can receive a defined waveform from transmit hardware. The system can transmit an output waveform with a defined modulation from the PA. The system can capture samples of the output waveform. The system can submit the samples to a processing system temporarily connected to a transmitter system. The system can compute a PA model using the defined waveform and the samples. The system can determine a plurality of Digital Pre-Distorter (DPD) coefficients for a plurality of power levels, frequencies, and temperatures based on the PA model. The system can store the plurality of DPD coefficients to a memory of the transmitter system. Additionally, the system can add predistortions using the plurality of DPD coefficients to a plurality of input waveforms to correct for impairments introduced by the PA.