Reconfigurable Nonlinear Filter for Digital Pre-Distortion
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Solution Overview
Problem
Low-cost power amplifiers in wireless communication devices are inherently nonlinear, leading to spectral emissions and in-band distortion, which existing digital pre-distortion technologies struggle to address effectively due to high power consumption and limited flexibility in RF processing chains.
Innovation Solution
A reconfigurable and scalable nonlinear filter circuit using programmable hardened circuitry and configurable hardware, incorporating adders, multipliers, and memories to store nonlinear parameters, allowing for flexible distortion of input signals and reducing power consumption without sacrificing flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If block random access memory and DSPs are used to implement nonlinear filters in digital pre-distorters, then the flexibility and broad range of DSP implementation are improved, but the die space and power consumption increase significantly
Solution Approach 1:
The patent segments the nonlinear filter implementation into dedicated hardware circuitry components (adders, multipliers, memory units) that can be selectively configured and activated. This segmentation allows the system to use only the necessary computational resources for each specific application, reducing overall power consumption while maintaining flexibility through selective activation of circuit segments.
Solution Approach 2:
The patent replaces the general-purpose mechanical/electronic system (DSPs and block RAM) with a customized hardware circuitry system specifically designed for nonlinear filter operations. This substitution creates a dedicated computational path that eliminates the overhead and power consumption associated with general-purpose processing while maintaining the required flexibility through configurable hardware interconnections.
2Ease of manufacture
If low-cost power amplifiers are used in RF processing chains, then the cost is reduced, but the linearity deteriorates due to inherent non-linearity
Solution Approach 1:
The patent applies preliminary action by implementing digital pre-distortion processing that intentionally pre-distorts the input signal before it reaches the power amplifier. This preliminary distortion is designed to counteract the amplifier's inherent non-linearity, so that when the amplifier processes the pre-distorted signal, the output becomes linear. This allows the use of low-cost non-linear amplifiers while achieving linear output characteristics.
Solution Approach 2:
The patent converts the harmful non-linearity of low-cost power amplifiers into a beneficial characteristic by characterizing the specific distortion pattern and then using configurable hardware circuitry to apply the inverse distortion to the input signal. This approach transforms the amplifier's defect into a predictable, correctable behavior, enabling cost-effective implementations that maintain signal integrity.
3Reliability
If digital pre-distortion processing is applied to correct distortions from nonlinear power amplifiers, then the linearity is improved, but the complexity of the RF processing chain increases
Solution Approach 1:
The patent applies dynamics by implementing configurable hardware circuitry that can be dynamically reconfigured based on the specific application requirements. The system can adapt its computational complexity, memory usage, and processing path to match the actual needs of different wireless applications (Macro, DAS, mMIMO), allowing linearity correction to be achieved with minimal complexity for each specific case rather than a fixed high-complexity architecture.
Solution Approach 2:
The patent utilizes parameter changes by allowing the nonlinear filter parameters (coefficients, memory depth, filter order) to be adjusted based on the specific application and amplifier characteristics. The configurable hardware circuitry can modify these parameters to optimize the balance between linearity correction performance and processing complexity, enabling the system to achieve sufficient linearity with appropriate parameter selection rather than maximum complexity.
Data Source
AI summary
Examples described herein provide a radio frequency circuit. The radio frequency circuit includes a controller; a parameter estimator circuit; a capture circuit; and a pre-distorter circuit. The pre-distorter generally includes one or more nonlinear filter circuits and configurable hardware circuitry. Each of the one or more the nonlinear filter circuits includes: adder(s); multiplier(s); and memories coupled to at least one of the adder(s) and the multiplier(s); where the configurable hardware circuitry is configured to distort one or more input signals by directing the one or more input signals along a path through the one or more adders, the one or more multipliers, and the one or more memories and by distorting the one or input signals using the nonlinear parameters stored in the one or more memories as the one or more input signals travels the path.