Digital Predistortion Feedback Calibration for Wideband Power Amplifiers
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Solution Overview
Problem
Existing digital predistortion methods for power amplifiers in wideband wireless communication systems, such as LTE, face challenges in achieving accurate delay calibration and high accuracy due to device jitter caused by temperature and time changes, leading to poor performance in adjacent channel power ratio (ACPR) and phase uniformity.
Innovation Solution
A digital predistortion processing method that involves extracting predistortion parameters, performing power amplification, collecting feedback signals, delaying the forward signal by a preset number of sampling points, and performing synchronous correlation calculations to calibrate the feedback signal, thereby training predistortion coefficients for improved ACPR and phase calibration without increasing hardware or software complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If device jitter compensation is implemented to address temperature and time changes, then phase uniformity improves, but system complexity increases
Solution Approach 1:
The patent implements feedback by collecting the forward transmission signal after power amplification, performing synchronous correlation calculation with the input signal, and using the correlation results to update predistortion coefficients. This closed-loop feedback mechanism compensates for device jitter caused by temperature and time changes, maintaining phase uniformity without requiring complex additional hardware.
Solution Approach 2:
The system uses itself to compensate for jitter by performing self-calibration through synchronous correlation calculation. The power amplifier's own output signal is correlated with the input signal to extract phase and amplitude information, which is then used to update predistortion coefficients, enabling the system to self-correct for environmental variations.
2Measurement precision
If synchronous correlation calculation is performed to calibrate feedback signal, then ACPR performance improves, but computational load increases
Solution Approach 1:
The patent extracts only the essential information needed for predistortion coefficient update through synchronous correlation calculation. By focusing on extracting amplitude and phase differences rather than processing the entire signal spectrum, the system achieves improved ACPR performance while minimizing computational load.
3Reliability
If predistortion coefficients are updated frequently to track nonlinear characteristics, then linearity improves, but processing time increases
Solution Approach 1:
The patent implements periodic updating of predistortion coefficients through synchronous correlation calculation. Instead of continuous updating, the system performs correlation-based coefficient updates at appropriate intervals, maintaining linearity performance while reducing processing time and avoiding unnecessary computations.
Data Source
AI summary
A digital predistortion processing method and system comprises extracting from a predistortion coefficient parameter table a predistortion parameter corresponding to an input signal, so as to predistort the input signal and obtain a forward transmission signal; amplifying the power of the forward transmission signal to obtain an output signal; acquiring the output signal to obtain a feedback signal; delaying a predetermined number of sampling points so as to acquire the forward transmission signal and obtain a reference signal; conducting synchronization-related calculation on the reference signal and the feedback signal, and calibrating the feedback signal; training a predistortion coefficient according to the reference signal and the calibrated feedback signal; and forming the predistortion coefficient parameter table according to the predistortion coefficient and the amplitude of the input signal. The present invention can delay a predetermined number of sampling points for a transmission signal, thus greatly improving radio frequency index (ACPR).