Time-Interleaved ADC Compensation Using Fixed Differentiator Filters
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Solution Overview
Problem
Existing methods for compensating frequency response mismatch errors in M-channel time-interleaved Analog-to-Digital Converter (ADC) arrays are cumbersome and costly, particularly for high-resolution, high-speed applications, as they often require online filter design and additional components like cosine and sine modulators.
Innovation Solution
A compensation method using fixed filters that approximate differentiators of various orders and a few variable multipliers, corresponding to parameters in polynomial models of the channel frequency responses, allowing for economical implementation and adjustment of multipliers as channel frequency responses change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If online filter design is used to compensate frequency response mismatch errors, then compensation accuracy is improved, but device complexity and implementation cost increase
Solution Approach 1:
The patent applies preliminary action by pre-designing and storing filter coefficients offline before actual operation. The compensation filters are designed in advance using polynomial models of channel frequency responses, and the coefficients are stored for later use. This eliminates the need for complex online filter design while maintaining high compensation accuracy, as the pre-computed coefficients are directly applied during ADC operation.
Solution Approach 2:
The patent uses copying by creating polynomial models that represent the channel frequency responses. Instead of designing complex filters for each channel, simplified polynomial approximations are created that capture the essential frequency response characteristics. These polynomial models are then used to generate compensation coefficients, significantly reducing implementation complexity while preserving accuracy.
2Measurement precision
If additional components like cosine and sine modulators are added for compensation, then frequency response mismatch compensation is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and compensates only for the essential frequency response mismatch characteristics using polynomial models. Instead of adding complex modulation components, the method extracts the key frequency response parameters and uses polynomial approximations to represent them. This allows effective compensation without introducing additional cosine and sine modulators or other complex hardware components.
Solution Approach 2:
The patent applies parameter changes by representing channel frequency responses using polynomial parameters rather than full complex filter parameters. The frequency response mismatches are characterized by a small number of polynomial coefficients that can be easily adjusted and stored. This parameter transformation simplifies the compensation mechanism, eliminating the need for additional modulator components while maintaining compensation effectiveness.
3Speed
If high-resolution, high-speed ADC conversion is achieved using time-interleaved architecture, then sampling rate is improved, but channel mismatch errors increase
Solution Approach 1:
The patent implements feedback by using the known polynomial models of channel frequency responses to generate compensation coefficients that are applied to correct the ADC output. The compensation process continuously adjusts the combined output signal based on the pre-characterized frequency response mismatches of individual channels. This feedback mechanism effectively suppresses channel mismatch errors while maintaining the high sampling rate advantage of the time-interleaved architecture.
Data Source
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AI summary
A method for the compensation of frequency-response mismatch errors in M -channel time- interleaved ADCs. The compensation is done by means of a technique that makes use of a number of fixed filters, that approximate differentiators of different orders, and a few variable multipliers that directly correspond to parameters in polynomial models of the M channel frequency responses. The invention further provides a compensated M -channel time- interleaved ADC based on and performing said method.