Wireless PA Calibration Using mDPD for Filter Ripple Compensation
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Solution Overview
Problem
Operating power amplifiers in electronic devices at peak efficiency is challenging due to the difficulty in compensating for non-linearities and parasitic rippling effects in wireless communications circuitry, especially in applications with intraband carrier aggregation and cascaded filters.
Innovation Solution
A calibration process is implemented to characterize the linear transformation between the radio-frequency amplifier and feedback receiver, generating memory digital predistortion (mDPD) coefficients to compensate for filter and parasitic effects, ensuring accurate power control and channel stability across power modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If power amplifiers are operated at peak efficiency, then power consumption is reduced, but non-linearities and parasitic rippling effects increase causing signal distortion
Solution Approach 1:
The system performs preliminary calibration to characterize the linear transformation between amplifier input and feedback receiver input, generating filter models and mDPD coefficients before actual operation. This preliminary characterization enables the system to compensate for non-linearities and parasitic effects in advance, allowing peak efficiency operation without signal distortion
Solution Approach 2:
The system uses feedback from the feedback receiver to continuously monitor the amplifier output and adjust the predistortion coefficients. The feedback path includes a filter model that characterizes the linear transformation, enabling real-time compensation of non-linearities and parasitic rippling effects while maintaining peak efficiency operation
2Measurement precision
If filter models are used to compensate for linear effects, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system introduces filter models as intermediary elements that characterize the linear transformation in the feedback path. These filter models act as mediators between the amplifier and feedback receiver, enabling accurate power control and compensation of linear effects without requiring direct complex measurements between the amplifier and feedback receiver
Solution Approach 2:
The system changes the parameters of the filter models during calibration to characterize different operating conditions. By adjusting and storing multiple filter model parameters corresponding to different power modes and frequency bands, the system achieves high measurement precision across varying operating conditions while managing complexity through parameter-based adaptation
3Productivity
If mDPD coefficients are generated through calibration, then spectral efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The system performs preliminary calibration procedures to generate mDPD coefficients before deployment. This preliminary action includes characterizing the linear transformation, creating filter models, and determining the relationship between amplifier input and feedback receiver input under various operating conditions, establishing an accurate baseline for spectral efficiency
Solution Approach 2:
The calibration process uses feedback measurements to iteratively refine the mDPD coefficients. By continuously measuring the amplifier output through the feedback receiver and comparing it with the expected output, the system adjusts the coefficients to minimize errors, achieving high spectral efficiency while managing manufacturing precision requirements through iterative refinement
4Stability of the object's composition
If the digital predistortion block is activated for compensation, then channel stability is improved, but power consumption increases
Solution Approach 1:
The system dynamically activates and deactivates the digital predistortion block based on operating conditions. The predistortion is activated when operating in modes requiring high linearity and channel stability, and deactivated when operating in modes where compensation is less critical, optimizing the trade-off between channel stability and power consumption in real-time
Data Source
AI summary
An electronic device may include wireless circuitry having a radio-frequency amplifier. A method for calibrating the wireless circuitry is provided that includes characterizing a linear transformation between an input of the radio-frequency amplifier and an input of a feedback receiver, where the radio-frequency amplifier has an output that is coupled to the input of the feedback receiver via a filter and a radio-frequency coupler, obtaining a filter model based on the characterized linear transformation, and generating memory digital predistortion (mDPD) coefficients for a digital predistortion block coupled to the input of the radio-frequency amplifier based on the filter model. The generation of the mDPD coefficients can alternatively be based on an inverse filter model and can further include minimizing an error signal computed from a difference between a predistorted signal output from the digital predistortion block and a demodulated signal output from the feedback receiver.