LUT-Based Memory DPD for Power Amplifier Linearity
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Solution Overview
Problem
Power amplifiers in wireless communication systems experience memory effects due to wideband signals, leading to nonlinearity and performance degradation, with existing polynomial-based memory DPD solutions resulting in high complexity and current consumption, and inability to adapt to varying PA characteristics.
Innovation Solution
A look-up table (LUT) based memory digital pre-distortion method that generates pre-distorted signals by tracking input signal amplitude and delay, and dynamically adjusts supply voltage and bias to reduce memory effects, using adaptive algorithms for real-time correlation and cross-correlation to establish and update LUTs, thereby improving PA linearity and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polynomial-based memory DPD is used to solve memory effect of PA, then PA linearity is improved, but device complexity and current consumption increase
Solution Approach 1:
The patent uses a look-up table (LUT) to store pre-calculated correction values that copy the ideal linearization behavior, replacing the need for complex real-time polynomial calculations. This LUT-based approach maintains PA linearity improvement while significantly reducing computational complexity and current consumption.
Solution Approach 2:
The correction values are pre-calculated and stored in the LUT during system initialization or manufacturing, rather than computing them in real-time during operation. This preliminary action eliminates the need for complex polynomial computations during signal processing, reducing both device complexity and power consumption.
2Manufacturing precision
If polynomial-based memory DPD is used to solve memory effect of PA, then PA linearity is improved, but current consumption increases
Solution Approach 1:
The LUT stores pre-computed correction values that replicate the polynomial-based linearization effect, allowing the system to achieve the same PA linearity improvement without performing energy-intensive polynomial calculations in real-time, thus reducing current consumption.
Solution Approach 2:
All computationally intensive polynomial calculations are performed in advance and stored in the LUT. During operation, the DPD circuit only performs simple table lookups and interpolations, which consume significantly less current compared to real-time polynomial evaluation.
3Manufacturing precision
If polynomial model is used for memory DPD, then memory effect is compensated, but the system cannot adapt to varying PA characteristics
Solution Approach 1:
The patent implements a tracking circuit that dynamically updates the LUT based on changing PA characteristics. As PA parameters drift over time or with temperature variations, the tracking circuit detects these changes and adjusts the LUT contents accordingly, enabling the system to adapt to varying PA characteristics while maintaining memory effect compensation.
Solution Approach 2:
The system incorporates a feedback mechanism where the tracking circuit monitors PA output and compares it with expected values, then uses this feedback information to update the LUT. This closed-loop approach ensures the DPD system continuously adapts to PA characteristic variations and maintains optimal performance.
Data Source
AI summary
A method of reducing memory effect of a power amplifier (PA), for a look-up table (LUT) based memory digital pre-distortion (DPD) circuit of an electronic device is disclosed. The method comprises generating a pre-distorted signal according to a LUT including parameters of an input signal amplitude and an input signal delay associated with a bandwidth of a signal inputted to the memory DPD circuit, and outputting the pre-distorted signal to the PA for improving the nonlinearity of the PA.