ADC INL Measurement Using Harmonic Phase and FFT Analysis
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Solution Overview
Problem
Conventional methods for determining integral non-linearity (INL) in analog-to-digital converters (ADCs) are time-consuming, inaccurate, and architecture-dependent, failing to account for phase distortion and requiring extensive resources.
Innovation Solution
A method involving a signal generator to transmit a periodic signal to an ADC, a signal transformer to determine harmonic phases and amplitudes, and an INL term calculator using Chebyshev Polynomial Approximation to calculate INL, which corrects for Fourier transform phase distortion, allowing for efficient and architecture-independent INL determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to determine INL in ADCs, then measurement accuracy can be achieved, but the determination time is excessively long and manufacturing efficiency is reduced
Solution Approach 1:
The patent changes the measurement parameters by using FFT-based frequency domain analysis instead of conventional time-domain methods. By transforming the ADC output signal into the frequency domain and analyzing harmonic components, the measurement process is accelerated while maintaining accuracy through proper parameter selection including window function application and frequency bin alignment
Solution Approach 2:
The patent substitutes complex conventional measurement mechanisms with a simplified FFT-based computational approach. Instead of using lengthy sequential measurement procedures, the invention uses efficient spectral analysis algorithms that can process the entire signal spectrum simultaneously, dramatically reducing measurement time while preserving measurement precision
2Measurement precision
If conventional INL determination methods are used, then results can be obtained, but the methods are architecture-dependent and require extensive resources
Solution Approach 1:
The patent creates a universal measurement method that works across different ADC architectures by using FFT-based spectral analysis. The approach is architecture-independent because it measures the actual output signal characteristics rather than relying on architecture-specific internal node measurements, making the method applicable to various ADC types including flash, pipeline, and sigma-delta converters
Solution Approach 2:
The patent extracts only the essential information needed for INL determination by focusing on harmonic component analysis in the frequency domain. Instead of processing the entire time-domain signal with complex algorithms, the method extracts specific frequency components (harmonics) that contain the INL information, simplifying the measurement system while maintaining accuracy
3Productivity
If conventional methods are used for INL determination, then measurements can be performed, but phase distortion effects are not accounted for reducing accuracy
Solution Approach 1:
The patent incorporates phase distortion compensation through a feedback mechanism where the measured harmonic phases are used to correct the INL calculation. The method measures the actual phase of each harmonic component and uses this information to compensate for phase distortion effects in the final INL determination, ensuring high accuracy while maintaining measurement efficiency
Solution Approach 2:
The patent applies preliminary signal processing actions including windowing and frequency alignment before the main INL calculation. By pre-processing the signal to account for phase effects and aligning the frequency bins properly before harmonic analysis, the method ensures that phase distortion is compensated in advance, maintaining both speed and accuracy
Data Source
AI summary
Methods and apparatus for determining non-linearity in analog-to-digital converters are disclosed. An example apparatus includes a signal interface to receive an output of an analog-to-digital converter (ADC), the output corresponding to a periodic signal transmitted to the ADC; a signal transformer to determine at least one of a harmonic phase or a harmonic amplitude corresponding to the output; and an integral non-linearity (INL) term calculator to determine the INL of the ADC based on a characteristic of the periodic signal and the at least one of the harmonic phase or the harmonic amplitude.