RF-ADC Nonlinearity Estimation for High-Order Distortion Correction
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Solution Overview
Problem
Existing nonlinearity correction techniques for radiofrequency analog-to-digital converters (RF-ADCs) fail to effectively compensate for high-order nonlinearity, particularly in delay-based ADC architectures, leading to residual mismatch between calibration and primary paths, and are limited by memory requirements and precision needs at lower input levels.
Innovation Solution
A blind nonlinearity estimation technique that uses online estimation circuitry to adaptively estimate and correct residual nonlinearity in RF-ADCs by selecting appropriate nonlinearity functions, generating terms, and determining coefficients, allowing for real-time compensation without prior knowledge of input data quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing nonlinearity correction techniques are used for RF-ADCs, then basic nonlinearity compensation is achieved, but high-order nonlinearity cannot be effectively compensated leading to residual mismatch
Solution Approach 1:
The patent changes the parameters of the nonlinearity correction approach by using online estimation techniques that adaptively determine nonlinearity coefficients for high-order terms. Instead of fixed correction parameters, the system dynamically estimates and updates coefficients based on real-time ADC output data, enabling effective compensation of high-order nonlinearity that was previously unaddressed
Solution Approach 2:
The system performs self-correction by using its own ADC output data to estimate and correct its nonlinearity. The online estimation circuitry processes the ADC's own output signals to generate correction terms, allowing the system to compensate for its high-order nonlinearity without requiring external calibration equipment or prior knowledge of the nonlinearity characteristics
2Adaptability or versatility
If blind nonlinearity estimation is implemented for real-time correction, then adaptability to various input levels is improved, but device complexity increases due to additional estimation circuitry
Solution Approach 1:
The patent segments the nonlinearity correction function into separate estimable terms (e.g., different orders of nonlinearity). Each term can be estimated and corrected independently through the online estimation process, allowing the complex problem of high-order nonlinearity compensation to be broken down into manageable computational steps that can be implemented with moderate circuit complexity
Solution Approach 2:
The patent introduces an intermediary estimation process that bridges the ADC output and the final corrected signal. The online estimation circuitry acts as a mediator that processes ADC outputs, extracts nonlinearity information, and generates correction terms without requiring direct access to the original analog input or complex external calibration systems
3Quantity of substance
If traditional nonlinearity correction methods are used, then memory requirements are reduced, but precision at lower input levels deteriorates
Solution Approach 1:
The patent implements dynamic adaptation of correction coefficients based on the actual input signal level. The online estimation technique continuously updates nonlinearity coefficients according to the current operating conditions, allowing the system to maintain high precision at lower input levels where nonlinearity effects are more pronounced, rather than using fixed coefficients optimized for a specific operating point
Data Source
AI summary
An example apparatus includes: nonlinearity function selection circuitry with an output, the nonlinearity function selection circuitry to select a type of a nonlinearity function, the nonlinearity function to model nonlinearity portions of data output from an analog-to-digital converter, nonlinearity function term generation circuitry with a first input coupled to the output, the nonlinearity function term generation circuitry to generate one or more nonlinearity function terms of the nonlinearity function based on the type of the nonlinearity function and the data, and coefficient determination circuitry with a second input coupled to the output, the coefficient determination circuitry to determine one or more nonlinearity function coefficients based on the one or more nonlinearity function terms, the nonlinearity portions of the data to be compensated based on the one or more nonlinearity function coefficients.