Time-Interleaved ADC Correction for Spur-Free Equalization
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Solution Overview
Problem
Time-interleaved analog-to-digital converters (TI-ADCs) generate significant voltage transients that electromagnetically couple to a second ADC, affecting the reference signal and causing errors such as spurs and offsets, which degrade the performance of the receiver.
Innovation Solution
An ADC system with a correction circuit that uses activity data to identify currently and optionally previously active sub-ADCs, employing look-up tables to generate correction data that mitigates these errors before the equalizer, combining this data with the second ADC output to improve the equalized signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If time-interleaved sub-ADCs are activated to capture wide RF spectrum, then the bandwidth coverage is improved, but voltage transients are generated that electromagnetically couple to the second ADC and degrade signal quality
Solution Approach 1:
The correction circuit proactively generates correction data based on the activity status of sub-ADCs before the electromagnetic coupling errors fully manifest in the second ADC output. By detecting which sub-ADCs are active and pre-calculating their coupling effects, the system compensates for errors in advance, allowing the time-interleaved architecture to operate at full bandwidth without degrading the reference signal quality.
2Measurement precision
If a second ADC is coupled in parallel to sense the input signal and create reference signal, then the equalization performance is improved, but the reference signal is corrupted by electromagnetic coupling from sub-ADCs
Solution Approach 1:
The system implements a feedback mechanism where the correction circuit continuously monitors the activity data from sub-ADCs and dynamically adjusts the correction data applied to the second ADC output. This closed-loop approach ensures that the reference signal remains accurate despite varying coupling conditions, maintaining both equalization performance and reference signal reliability simultaneously.
Solution Approach 2:
The correction circuit acts as an intermediary between the time-interleaved sub-ADCs and the second ADC. It processes the activity data and generates correction data that mediates the harmful electromagnetic coupling effects, allowing the second ADC to produce a clean reference signal that can be used for optimal equalization without being corrupted by sub-ADC transients.
3Reliability
If correction circuit with look-up tables is implemented to mitigate errors, then the signal quality is improved, but the device complexity increases
Solution Approach 1:
The look-up tables are pre-computed and stored during system initialization or manufacturing, containing correction data for all possible sub-ADC activity patterns. During operation, the correction circuit simply queries these pre-computed tables based on current activity data, avoiding the need for complex real-time calculations. This approach significantly improves signal quality while keeping the runtime circuit complexity manageable.
Solution Approach 2:
The correction circuit uses the activity data from the sub-ADCs to automatically generate the appropriate correction data without requiring external intervention or complex processing. The look-up tables enable the system to self-correct the electromagnetic coupling errors based solely on the observed activity patterns, improving signal quality through an autonomous, relatively simple correction mechanism.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed technique significantly reduces spurs and offsets in the equalized output, enhancing the ADC system's performance by correcting errors caused by electromagnetic coupling between sub-ADCs.
Implementation Method 1
The activation of time-interleaved sub-ADCs can generate significant voltage transients electromagnetically coupling to the second ADC and having an impact on the reference signal
Data Source
AI summary
An analog-to-digital converter (ADC) system is provided. The ADC system includes a first signal path. The first signal path includes a first ADC configured to generate first digital data based on an input signal. The first ADC is a time-interleaved ADC including a plurality of sub-ADCs. The first signal path further includes circuitry configured to output activity data indicating at least which of the plurality of sub-ADCs is currently active. The ADC system further includes a correction circuit configured to output digital correction data based on the activity data. Further, the ADC system includes a second signal path coupled in parallel to the first signal path. The second signal path includes a second ADC configured to generate second digital data based on the input signal and a combiner circuit configured to generate modified second digital data by combining the second digital data and the correction data. The ADC system further includes an equalizer configured to generate an equalized output signal of the ADC system based on the first digital data. The equalizer is configured to adjust, based on the modified second digital data, at least one equalization parameter used for generating the equalized output signal of the ADC system.