Time-Interleaved ADC Calibration Using a Randomized Reference Path
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Solution Overview
Problem
Time-interleaved analog-to-digital converter (ADC) systems face challenges in maintaining high spurious free dynamic range (SFDR) without increasing the noise floor, as distortions from component variations and physical path differences lead to reduced SFDR and elevated noise levels, with existing calibration methods providing only static corrections and randomized selection methods converting distortions to random noise.
Innovation Solution
A time-interleaved ADC system with a reference ADC that converts the analog signal into a digital reference signal at a lower average sampling rate, using a pseudo-random pattern to select ADCs for correction, and a correction module that adjusts digital signals based on the reference signal and selected ADC signals to remove mean residual errors, thereby improving SFDR with minimal SNR degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If static calibration is used during manufacturing, then manufacturing precision is improved, but adaptability deteriorates because it does not account for distortions that change during operation
Solution Approach 1:
The patent transitions from static calibration to dynamic adaptive calibration. The correction module continuously updates correction parameters during operation based on real-time distortion measurements, allowing the system to adapt to changing conditions while maintaining high precision correction
2Measurement precision
If randomized selection of streams is used, then SFDR is improved, but noise floor increases because distortions are converted to random noise
Solution Approach 1:
The patent employs feedback-based adaptive calibration where the correction module continuously measures distortion using the digital signal processor and updates correction parameters accordingly. This feedback mechanism eliminates the need for randomized selection while maintaining high SFDR and avoiding noise floor elevation
Solution Approach 2:
The system performs self-calibration using its own resources. The digital signal processor utilizes available computational resources to calculate correction parameters in real-time, and the correction module automatically applies these corrections without requiring external calibration equipment or randomized stream selection
3Productivity
If time-interleaved parallel ADCs are used, then productivity is improved by achieving higher sampling rates, but measurement precision deteriorates due to component spread and physical path differences causing distortions
Solution Approach 1:
The correction module acts as an intermediary that processes and corrects the digital signals from multiple parallel ADCs. It calculates distortion parameters and applies correction factors to each ADC's output, eliminating inter-ADC distortion while preserving the high sampling rate capability of the time-interleaved architecture
Solution Approach 2:
The patent replaces physical calibration mechanisms with digital signal processing-based correction. Instead of using hardware adjustments or randomized selection, the system uses a digital correction module that computationally eliminates distortions, maintaining high SFDR while preserving the parallel ADC architecture's productivity benefits
Data Source
AI summary
It is provided a provided a time-interleaved analog-to-digital converter (ADC) system comprising an input port configured to receive an analog signal, an ADC-array comprising M, M≥2, ADCs arranged in parallel. Each ADC is configured to receive and to convert a portion of the analog signal into a digital signal at a sample rate fs. The ADC-system further comprises a reference ADC configured to receive and to convert the analog signal into a digital reference signal at an average sampling rate fref lower than fs. Each sampling instant of the reference ADC corresponds to a sampling instant of an ADC in the array of ADCs, and the ADC to select for each reference ADC sampling instant is randomized over time. The ADC-system also comprises a correction module configured to adjust the digital signal outputs of the ADC-array into a corrected digital output signal based on samples of the digital reference signal and the digital signals from the corresponding selected ADCs. It is also provided a method for time-interleaved analog-to-digital conversion.