Interleaved ADC DSA-Range Calibration for IL Mismatch Correction
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Solution Overview
Problem
Interleaved ADC systems face issues with interleaving mismatches due to gain, delay, and bandwidth mismatches in component ADCs, leading to spurious components that degrade SFDR, SNR, and ENOB, which are exacerbated by digital step attenuation (DSA) in the receiver chain.
Innovation Solution
An IL mismatch estimation engine with selective estimation allocation and blanking is implemented to select IADC data within allocated DSA setting subranges, aggregating data to provide IL mismatch estimates and correction parameters, and a DSA statistics collector ensures efficient allocation strategies based on DSA setting distribution statistics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If digital step attenuation (DSA) is introduced to dynamically adjust RX signal power to the input range of ADCs, then automatic gain control is achieved, but interleaving mismatches (IL mismatches) occur that depend on the active DSA attenuation setting, causing spurs/images and degrading SFDR, SNR, and ENOB
Solution Approach 1:
The system performs preliminary characterization of IL mismatches across different DSA attenuation settings during calibration. The IL mismatch estimation engine pre-computes and stores mismatch parameters for each DSA setting, which are then applied during normal operation to compensate for the mismatches before they affect performance.
Solution Approach 2:
The system changes parameters by introducing correction factors based on the active DSA setting. The IL mismatch correction selectively adjusts the gain/phase parameters of interleaved ADC channels depending on which DSA attenuation step is currently active, thereby compensating for setting-dependent mismatches.
2Speed
If multiple component ADCs are used to achieve high effective sampling rate through interleaving, then sampling rate is increased, but mismatches in gain/delay/bandwidth of component ADCs cause interleaving mismatches that degrade performance
Solution Approach 1:
The system applies local quality correction by independently adjusting the gain, phase, and timing parameters for each interleaved ADC channel based on its specific mismatch characteristics. The IL mismatch correction is tailored to each channel's performance rather than applying a uniform correction to all channels.
Solution Approach 2:
The system performs preliminary measurement and characterization of each component ADC's gain, delay, and bandwidth mismatches during calibration. These pre-measured parameters are stored and used to compute correction factors that are applied during normal operation to compensate for the mismatches.
3Measurement precision
If IL mismatch correction is applied across all DSA settings, then performance is improved, but complexity increases due to the need to track and correct mismatches for each DSA setting
Solution Approach 1:
The system segments the DSA attenuation range into multiple discrete steps, with each step having pre-characterized IL mismatch parameters. This segmentation allows the correction system to handle each setting independently using lookup tables or pre-computed correction factors, reducing the complexity of real-time calculations.
Solution Approach 2:
The system implements self-service by automatically selecting and applying the appropriate IL mismatch correction parameters based on the currently active DSA setting. The IL mismatch estimation engine autonomously monitors the DSA setting and applies the corresponding correction without requiring manual intervention or complex decision logic.
Data Source
AI summary
An interleaved ADC receives an RX signal attenuated by a DSA based on an active DSA setting, within a range of DSA settings (DSA setting range) corresponding to selectable attenuation steps, the DSA setting range partitioned into a number of DSA setting subranges (DSA subranges). The ADC includes an IL mismatch estimation engine in the digital signal path, with an estimation subrange blanker, and an IL mismatch estimator. The estimation subrange blanker is coupled to receive the IADC data stream, and responsive to a DSA subrange allocation signal to select, in each of successive aggregation cycles, IADC data corresponding to an active DSA setting that is within an allocated DSA subrange (DSA active data within an DSA allocated subrange). The IL mismatch estimator aggregates, during each aggregation cycle, IL mismatch estimation data based on the selected DSA active data within the DSA allocated subrange, generates an estimate of IL mismatch (IL mismatch estimate) based on the aggregated IL mismatch estimation data, generates IL mismatch correction parameters based on the aggregated IL mismatch estimation data, and generates IL mismatch estimate uncertainty data corresponding to an uncertainty in the IL mismatch estimate used to generate the associated IL mismatch correction parameters for the DSA allocated subrange. A DSA statistics collector to collect a distribution of DSA settings over a pre-defined time period (DSA setting distribution statistics). An estimation subrange allocator coupled to receive DSA setting distribution statistics, and the IL mismatch estimate uncertainty data, and to provide to the estimation subrange blanker the DSA subrange allocation signal according to a pre-defined allocation strategy.