Time-Interleaved ADC Frequency-Domain Calibration for Channel Mismatch
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Solution Overview
Problem
Existing time-interleaved ADC error correction methods face challenges in accurately estimating and correcting DC offset, gain, sampling time, and bandwidth errors, requiring high precision analog circuits and often failing to distinguish DC input signals, leading to potential elimination of DC signals and inadequate bandwidth correction.
Innovation Solution
A method for extracting and correcting error parameters in time-interleaved ADCs by converting time domain signals to frequency domain, calculating error parameters, and correcting them independently in the frequency domain, using a reference channel to adjust other channels, employing least mean square algorithms for PVT tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DC offset calibration is performed by integrating subchannel ADC output signals for a long time to obtain mean value, then DC offset error can be obtained and corrected, but the method cannot distinguish DC input signals which may result in elimination of DC signals
Solution Approach 1:
The patent extracts the DC component from the time-domain signal by performing FFT transformation to convert to frequency domain, where the DC offset can be identified as a specific frequency component (zero frequency). This allows separation of DC offset from actual DC input signals, enabling accurate calibration without eliminating valid DC signals.
2Measurement precision
If gain error calibration is performed by estimating average power of output signal, then gain error can be corrected, but if input signal frequency is fs/2M the power estimate changes with sampling time and gain error cannot be correctly estimated
Solution Approach 1:
The patent transforms the gain calibration problem from the time domain to the frequency domain using FFT. In the frequency domain, gain errors manifest as amplitude variations at specific frequency bins, which can be measured independently of sampling time variations. This dimensional transformation eliminates the interference of sampling time on power estimation.
3Measurement precision
If mixed-signal calibration algorithm is used to calibrate sampling time deviation, then sampling time error can be calibrated, but high analog circuit precision is required and accuracy of analog domain adjustment determines performance
Solution Approach 1:
The patent replaces the analog/mixed-signal calibration approach with a fully digital calibration method. By using FFT to convert time-domain signals to frequency domain, sampling time deviations manifest as phase differences at different frequency bins. These phase differences can be measured and corrected using digital signal processing, eliminating the need for high-precision analog circuits and analog domain adjustments.
4Measurement precision
If bandwidth error correction is attempted in later stages, then correction may be achieved, but under reasonable area and power consumption the influence of inter-channel bandwidth errors is difficult and sometimes nearly impossible to correct
Solution Approach 1:
The patent performs bandwidth calibration in the frequency domain by comparing the frequency response of different subchannels. By identifying bandwidth variations at different frequency points and applying compensatory filtering, the method corrects bandwidth errors before they affect the final output. This preliminary correction in the frequency domain is more efficient than attempting correction in the time domain, achieving better results with reduced power and area overhead.
Data Source
AI summary
A time-interleaved ADC error parameter extraction and correction method relates to an error correction technique for an analog-to-digital converter (ADC). This application discloses a method for extracting and correcting error parameters in a time-interleaved ADC, which takes the time-interleaved ADC channel n as the basis or reference channel, and corrects other channels to match the channel n. The steps include: a. Converting a time domain signal output of each ADC channel into a frequency domain signal; b. Calculating one or more error parameters according to the frequency domain signal; c. Correcting the frequency domain signal in one or more different channels according to the error parameter(s); and d. Converting the corrected frequency domain signal into a (corresponding) corrected time domain signal.