Multipath ADC Digital Calibration for Gain, Bandwidth, and Timing Mismatch
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Solution Overview
Problem
Multipath analog to digital converters (ADCs) face challenges in correcting mismatches and errors between subconverters, particularly in terms of gain, bandwidth, and timing, which degrade the accuracy and efficiency of signal conversion, and existing calibration methods are either offline or limited in their ability to address these issues effectively.
Innovation Solution
A system and method that includes a signal-stream correction subsystem, statistical measure subsystem, and measure integration subsystem to estimate and correct mismatches by producing a correction stream, which can be implemented in both digital and mixed analog/digital forms, capable of adapting to various types of mismatches and signal statistics, both stationary and cyclostationary, to improve the accuracy and reliability of the output digital stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multipath ADCs combine multiple subconverters to increase sampling rate, then the bandwidth and speed of conversion are improved, but mismatches between subconverters (gain, bandwidth, timing) degrade the accuracy of the output signal
Solution Approach 1:
The patent implements feedback-based calibration where the corrected digital output is fed back through a digital-to-analog converter and compared with the original analog input. This feedback loop enables continuous measurement and correction of mismatches between subconverters, maintaining high sampling rates while improving output accuracy through iterative error correction
Solution Approach 2:
The system dynamically adjusts correction parameters (gain, bandwidth, timing offsets) for each subconverter based on measured mismatches. By changing these parameters in real-time through digital signal processing, the system compensates for subconverter variations and maintains high measurement precision across all channels
2Measurement precision
If offline calibration is performed to correct subconverter mismatches, then the measurement precision is improved, but the productivity is reduced due to system downtime and interference with normal operation
Solution Approach 1:
The system performs preliminary calibration actions continuously in the background during normal operation. By preparing correction data through ongoing measurement and update processes, the system eliminates the need for separate offline calibration events, maintaining both high precision and continuous productivity
Solution Approach 2:
The calibration process operates continuously alongside normal conversion operations rather than interrupting them. Multiple subconverters can operate in parallel with continuous calibration updates, ensuring that measurement precision is maintained without reducing system availability or productivity
3Measurement precision
If complex calibration algorithms are implemented to correct all types of mismatches, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent replaces complex analog correction circuitry with digital signal processing algorithms. By using digital computation to calculate and apply correction factors, the system achieves high measurement precision while reducing hardware complexity, as digital processors can implement sophisticated algorithms without requiring proportionally complex physical circuits
Solution Approach 2:
The correction system uses a universal digital processing architecture that can handle multiple types of mismatches (gain, bandwidth, timing) through a single integrated algorithm framework. This multi-functional approach corrects various error sources without requiring separate dedicated circuitry for each error type, thereby reducing overall device complexity
4Productivity
If more subconverters are added to further increase sampling rate, then the productivity is improved, but the manufacturing precision deteriorates due to increased variability and mismatches
Solution Approach 1:
The system implements individual feedback calibration for each subconverter, measuring and correcting their specific mismatches regardless of how many subconverters are used. This per-channel feedback approach ensures that adding more subconverters to increase sampling rate does not degrade overall precision, as each channel is independently optimized
Solution Approach 2:
The system dynamically adjusts correction parameters for each subconverter based on measured characteristics, compensating for manufacturing variations. By changing these parameters digitally, the system maintains consistent precision across all subconverters even when additional channels with different characteristics are added to the multipath structure
Data Source
AI summary
A system and method of reducing the effects of nonidealities of ADCs in multipath converters is disclosed. The system and method employs a variety of measure and correction blocks to determine statistical properties of the output stream of the multipath converter and to apply corrections to the operation of the subconverters of the multipath converter based upon differences in the measured statistics and expected target values, either explicit or implicit, for those statistics. A variety of examples of possible measure and configuration blocks are disclosed, as is the cascading of the measure and correction blocks to correct multiple errors in the output of the multipath converter. Feedforward (purely digital) and feedback (analog and digital) solutions are both disclosed.