Multi-Stage ADC Piecewise Calibration via Delay-Signal Bypass
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Solution Overview
Problem
Existing analog-to-digital converters face challenges in operating at high speeds with reduced area and power requirements, particularly in radio-frequency sampling receivers, and struggle with calibrating non-linear stages which are highly non-linear and difficult to calibrate using signals generated by preceding stages.
Innovation Solution
The proposed analog-to-digital converter employs a voltage-to-delay device with a calibration engine/controller that selects pre-amplifiers from an array to generate delay signals, using a bypass line to directly apply delay signals to intermediate stages, allowing for piecewise calibration and reducing non-linearity by bypassing earlier stages' non-linear outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If delay-based stages are used to operate at high speed with reduced area and power, then speed and power efficiency are improved, but non-linearity in successive stages increases making calibration difficult
Solution Approach 1:
The ADC is divided into multiple delay-based stages, with the first stage processing the input signal and successive stages processing residual signals. Each stage is independently calibratable, allowing precise adjustment of individual stage characteristics while maintaining overall high-speed operation.
Solution Approach 2:
A bypass line is introduced as an intermediary path that allows the output of the first delay-based stage to be directly fed to intermediate successive delay-based stages, circumventing the non-linear transformation of intermediate stages during calibration. This enables accurate calibration of later stages without being affected by preceding stage non-linearities.
2Measurement precision
If successive delay-based stages process signals sequentially, then conversion precision is improved, but area and power consumption increase
Solution Approach 1:
The bypass line provides a partial action path that allows certain stages to be skipped during specific operations. The intermediate successive delay-based stages can be bypassed when calibrating later stages, reducing the active circuit area and power consumption while maintaining the precision benefits of multi-stage processing when needed.
3Ease of operation
If calibration signals from preceding stages are used, then calibration process is simplified, but non-linearity of preceding stages degrades calibration accuracy
Solution Approach 1:
The bypass line acts as an intermediary that provides a clean, linear signal path from the first delay-based stage directly to intermediate successive stages. This bypass path delivers calibration signals that have not been degraded by the non-linear transformations of intermediate stages, enabling both simple and accurate calibration.
Solution Approach 2:
The bypass line preserves the original delay signal characteristics from the first stage before they are transformed by intermediate stages. This preliminary preservation of signal integrity allows calibration to be performed with high accuracy using signals that have not yet been corrupted by non-linearities.
Data Source
AI summary
An analog-to-digital converter includes a voltage-to-delay device, such as a pre-amplifier array, for generating a delay signal based on a first voltage, and delay-based stages for generating digital signals based on the delay signal. In operation, the delay signal is transmitted to a first delay-based stage, or to an intermediate delay-based stage, bypassing the first delay-based stage, to overcome non-linearity of previous stages. If desired, different pre-amplifiers may be used to generate signals for calibration of different delay-based stages. The present disclosure may also involve converting to pseudo-static signals before signals are handed over to a calibration engine, to ease timing and preserve interface area and power. If desired, simple delay elements may be used to correct for non-linearity in a delay-based analog-to-digital converter. The present disclosure may be employed, if desired, in connection with any suitable cascade of non-linear stages.