Cryogenic Interface Circuit for Single-Cable Noise Suppression
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Solution Overview
Problem
Cryogenic systems face challenges in reducing noise from ground loops, electromagnetic interference, and thermal differences between sensors and control equipment while maintaining a single input-output channel, leading to increased wiring complexity and heat loading, which limits the number of devices that can be operated simultaneously.
Innovation Solution
A noise suppressing interface circuit with a low-pass filter and high impedance dc bypass line is implemented on an intercept board, allowing for noise suppression and biasing of superconducting devices using a single coaxial cable, reducing wiring complexity and heat loading by combining dc and rf signals into a single channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If separate input and output electrical channels are used for cryogenic amplifier with sensor, then noise suppression is improved, but wiring complexity increases
Solution Approach 1:
The patent combines separate input and output electrical channels into a single shared coaxial cable that carries both DC bias signals and RF readout signals simultaneously. This merging approach reduces wiring complexity while maintaining noise suppression through the use of a bias-tee circuit that separates the combined signals at the amplifier stage.
Solution Approach 2:
The single coaxial cable is designed to serve multiple functions: it provides both DC bias voltage delivery and RF signal readout pathways. The bias-tee circuit at the amplifier enables this multi-functionality by separating the combined DC and RF components, allowing one cable to replace what would traditionally require two separate cables.
2Reliability
If multiple electrical lines are run to cryostat feedthrough, then device performance is maintained, but heat loading increases
Solution Approach 1:
Multiple electrical lines carrying DC bias and RF readout signals are merged into a single coaxial cable transmission path. This reduction in the number of physical lines entering the cryostat directly reduces heat loading while the bias-tee circuit ensures that device performance is maintained by properly separating and processing the combined signals.
3Productivity
If more devices are operated simultaneously in cryogenic system, then system capability is improved, but wiring space requirements increase
Solution Approach 1:
The patent implements a merged single-cable architecture that allows multiple devices to share common transmission pathways. By combining DC bias and RF readout into one coaxial cable per device, and potentially sharing cables between multiple devices through multiplexing, the wiring space requirements are reduced, enabling higher device density in the cryogenic system.
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 solution effectively reduces noise-induced fluctuations and back currents, enabling sensitive device biasing and operation with fewer electrical channels, thus allowing for more complex and larger cryogenic systems to be integrated into smaller coolers.
Implementation Method 1
provides a low-pass filter in a dc-shunt line, which works to remove noise fluctuations propagating from room temperature
Implementation Method 2
A high impedance dc bypass line provides that dc currents induced by metallic connections between two different thermal environments are reduced by the high impedance dc path between those two temperatures
Data Source
AI summary
A thermal and environmental noise suppressing interface circuit which is configured to operate cold and is configured to perform biasing with suppression of noise currents from room temperature noise voltages and dc coupled rf readout of a superconducting device under test with a single coaxial cable or equivalent conductor pair. The circuit is configured to suppress the propagation of thermal and environmental noises to/from sensors operating at a different temperature from its operating and control equipment while maintaining a single input-output channel, and provides for the placement of a local grounding impedance on an intercept board.