ADC Digital Equalization with Background Nonlinear Calibration
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Solution Overview
Problem
Existing methods for digital equalization of analog-to-digital converters (ADCs) face challenges in reducing power consumption and efficiently tracking analog impairments without interrupting the processing of the main input signal, with off-line calibration being costly and reference ADC calibration being slow and noisy.
Innovation Solution
A method involving the addition of a reference signal to the input signal, which is used to adapt a non-linear equalizer (NLEQ) in the background without stopping the ADC processing, using a sequence of sinusoids or noise-like signals to estimate and remove harmonics, allowing for efficient coefficient adaptation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If off-line calibration is used to equalize ADC, then manufacturing precision is improved, but productivity deteriorates due to system interruption
Solution Approach 1:
The patent applies preliminary action by performing equalization calibration in the background before main signal processing begins. The calibration phase prepares the equalizer coefficients in advance, allowing the system to achieve high equalization precision without interrupting subsequent productivity-critical signal processing operations.
Solution Approach 2:
The patent implements periodic action by alternating between calibration phases and signal processing phases. The system periodically updates equalizer coefficients during designated calibration intervals while maintaining continuous or near-continuous main signal processing, thus balancing precision requirements with productivity demands.
2Adaptability or versatility
If reference ADC calibration is used to track analog impairments, then adaptability is improved, but measurement precision deteriorates due to noise
Solution Approach 1:
The patent uses a reference signal as an intermediary carrier to transfer impairment information. Instead of directly measuring impairments through a noisy reference ADC during normal operation, the system injects a known reference signal and uses its distorted version as an intermediary to extract impairment characteristics, thereby improving measurement precision while maintaining adaptability.
Solution Approach 2:
The patent creates a copied version of the reference signal that passes through the ADC under test. By comparing the original reference signal with its distorted copy, the system can accurately track analog impairments without being affected by the noise inherent in direct measurement approaches.
3Productivity
If reference signal injection is used to adapt equalizer, then productivity is improved by continuous processing, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the reference signal injection mechanism to serve multiple functions simultaneously. The same reference signal path is used for both calibration and continuous tracking of analog impairments, eliminating the need for separate dedicated hardware paths and thereby reducing overall system complexity while maintaining productivity.
Solution Approach 2:
The patent merges the calibration function and the tracking function into a unified reference signal processing path. By combining these functions that were traditionally separate, the system achieves continuous processing capability without proportionally increasing device complexity, as the merged structure shares common hardware resources.
Data Source
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AI summary
A system and method for equalization of a linear or non-linear system. The system includes an adder configured to add an analog reference signal and an input signal, a processing system configured to process a sum of the analog reference signal and the input signal, a non-linear equalizer (NLEQ) configured to process an output of the processing system to remove a distortion incurred by the processing system, a calibration circuitry configured to generate a reconstructed reference signal in digital domain based on measurement of the analog reference signal, and generate coefficients for the NLEQ based on the reconstructed reference signal and the output of the processing system, and a subtractor configured to subtract the reconstructed reference signal from an output of the NLEQ. The analog reference signal may be a sinusoid including single or multiple tones of sinusoids. The non-linear system may be an analog-to-digital converter (ADC).