Superconducting Sigma-Delta ADC Resonator Isolation Using SQUID Coupling
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Solution Overview
Problem
Higher-order bandpass Analog-to-Digital Converters (ADCs) have not been achieved in fully superconducting technology due to the lack of suitable components for isolating resonators, which is crucial for noise shaping and performance enhancement.
Innovation Solution
A superconducting Nth-order bandpass sigma—delta ADC is developed using a sequence of stages with resonators, where active superconducting components, such as SQUID amplifiers and Josephson transmission lines, directionally couple resonator pairs to electrically shield higher-order resonators from lower-order ones, achieving isolation without semiconductor components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If higher-order bandpass ADCs are implemented in superconducting technology, then noise shaping performance and sampling rate are improved, but isolation between resonators becomes difficult to achieve
Solution Approach 1:
A SQUID amplifier is introduced as an intermediary component between resonators to provide electrical isolation. The SQUID amplifier acts as a mediator that couples resonators while maintaining isolation, solving the problem of achieving proper isolation between higher-order resonators in superconducting bandpass ADCs without using semiconductor components.
Solution Approach 2:
The patent changes the operational parameters by using superconducting components operating at cryogenic temperatures, which enables high-Q resonators and SQUID amplifiers to function. This parameter change (temperature and material state) allows achieving both high noise shaping performance and proper resonator isolation simultaneously.
2Reliability
If semiconductor components are used for resonator isolation, then isolation performance is improved, but the ADC is no longer fully superconducting
Solution Approach 1:
The patent replaces semiconductor-based isolation mechanisms with superconducting SQUID amplifier-based isolation. The SQUID amplifier, being a superconducting device, substitutes for traditional semiconductor components while maintaining the required isolation function, thus preserving the fully superconducting nature of the ADC.
Solution Approach 2:
The SQUID amplifier serves multiple functions: it provides resonator isolation, signal amplification, and maintains superconducting operation. This multi-functionality allows a single superconducting component to replace what would traditionally require separate semiconductor isolation components, maintaining both isolation performance and fully superconducting operation.
3Ease of manufacture
If first-order single-stage ADCs are used, then implementation is simpler, but noise shaping and accuracy are limited
Solution Approach 1:
The ADC is segmented into multiple stages with multiple resonators (higher-order configuration). Each stage contributes to the overall noise shaping performance, and the SQUID amplifier enables proper coupling between segments. This segmentation allows achieving superior noise shaping and accuracy compared to first-order single-stage designs.
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
This approach enables high-performance bandpass ADCs with unprecedented sampling rates and accuracy, demonstrating effective noise shaping and improved signal processing capabilities.
Implementation Method 1
a superconducting quantum interference device (SQUID) amplifier, which is inductively coupled to the higher order resonator
Implementation Method 2
a Josephson transmission line (JTL), which is configured to electrically connect the SQUID amplifier to the lower order resonator
Implementation Method 3
A further known generalization of ΣΔ modulators is achieved by replacing the integrators by high-Q resonators. This suppresses the quantization noise at a resonant frequency
Data Source
AI summary
A superconducting Analog-to-Digital Converter (ADC) employing rapid-single-flux-quantum (RSFQ) logic is disclosed. The ADC has only superconductor active components, and is characterized as being an Nth-order bandpass sigma-delta ADC, with the order “N” being at least 2. The ADC includes a sequence of stages, which stages include feedback loops and resonators. The ADC further includes active superconducting components which directionally couple resonator pairs of adjacent stages. The active superconducting components electrically shield the higher order resonator from the lower order resonator. These active superconductor components include a superconducting quantum interference device (SQUID) amplifier, which is inductively coupled to the higher order resonator, and may include a Josephson transmission line (JTL), which is configured to electrically connect the SQUID amplifier to the lower order resonator. The first stage of ADC may employ an implicit feedback loop.