Josephson Junction AC Switch for Cryogenic Microwave Routing
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Solution Overview
Problem
Conventional microwave switches are not compatible with on-chip integration and cryogenic operation due to incompatible fabrication processes and high power dissipation, and tunable filters face challenges with control by single flux quantum technologies and operation at cryogenic temperatures, leading to issues like high return loss, limited bandwidth, and poor out-of-band isolation.
Innovation Solution
A superconducting AC switch system using Josephson junctions (JJs) with a magnetic field generator to modulate impedance, allowing on-chip integration and tunable impedance switching, achieving an on/off ratio greater than 20 dB from DC to 15 GHz, and supporting band-pass functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional microwave mechanical and electro-mechanical switches are used, then switching function is achieved, but on-chip integration compatibility is lost due to incompatible fabrication processes
Solution Approach 1:
The patent replaces mechanical switch structures with superconducting Josephson junction-based switches that operate without moving parts. The switching mechanism uses quantum tunneling effects in Josephson junctions controlled by magnetic fields or current, eliminating the need for mechanical components incompatible with semiconductor fabrication processes.
Solution Approach 2:
The patent changes the operating parameters from conventional temperature and voltage switching to cryogenic temperature operation with superconducting materials. By operating at temperatures below the superconducting critical temperature and using magnetic field or current control instead of mechanical actuation, the system achieves on-chip integration compatibility while maintaining switching functionality.
2Temperature
If conventional microwave switches are used, then switching function is achieved, but power dissipation becomes excessive for cryogenic operation
Solution Approach 1:
The patent exploits the superconducting phase transition by operating the switch in the superconducting state where resistance is zero. The Josephson junctions operate below the critical temperature of the superconducting material, allowing current to flow without resistive heating, thus enabling cryogenic operation with minimal power dissipation.
Solution Approach 2:
The patent replaces conventional resistive switching mechanisms with superconducting quantum tunneling switching. The Josephson junction provides non-dissipative switching through quantum mechanical effects, eliminating the I²R power losses that plague conventional switches at cryogenic temperatures.
3Adaptability or versatility
If tunable filters with active components like varactors are used, then frequency tuning is achieved, but control by single flux quantum technologies becomes difficult
Solution Approach 1:
The patent changes the control mechanism from voltage-controlled varactors to magnetic field-controlled or current-controlled Josephson junctions. The switching and tuning is achieved by applying magnetic flux or current pulses that exploit the Josephson effect, making the device directly controllable by single flux quantum technologies without requiring voltage-controlled active components.
4Temperature
If ferroelectric and ferrite materials are used in tunable filters, then frequency tuning is achieved, but operation at cryogenic temperatures becomes problematic
Solution Approach 1:
The patent uses the superconducting phase transition as the basis for both operation and tuning. By operating below the critical temperature of the superconducting material and controlling the Josephson junction parameters through magnetic field or current, the system achieves frequency tuning capability that is inherently compatible with cryogenic operation, unlike ferroelectric and ferrite materials.
5Temperature
If superconducting microwave filters are used, then cryogenic operation is achieved, but return loss becomes high
Solution Approach 1:
The patent dynamically changes the impedance parameters of the Josephson junction by controlling the magnetic field or current applied to it. By adjusting the critical current or plasma frequency of the Josephson junction, the system can match impedance to minimize reflection and reduce return loss, while maintaining cryogenic operation benefits.
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 system provides efficient microwave signal routing and modulation with high on/off ratios and tunable impedance, facilitating on-chip integration and improved bandwidth, addressing the limitations of conventional switches and filters.
Implementation Method 1
a magnetic field generator that is configured to switch from inducing a magnetic field in a plane of the one or more JJs, and providing no magnetic field in the plane of the one or more JJs
Implementation Method 2
A superconducting AC switch system uses Josephson junctions (JJs) with a magnetic field generator to modulate impedance
Implementation Method 3
A superconducting AC switch system uses Josephson junctions (JJs) with a magnetic field generator to modulate impedance, allowing on-chip integration and tunable impedance switching
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A superconducting AC switch system (10, 30) includes a switch network configuration (12, 40, 60, 90, 130) comprising a Josephson junction (JJ, 18) coupled to a transmission line (42, 62, 92, 132) having a transmission line impedance, and a magnetic field generator (16, 32) that is configured to switch from inducing a magnetic field in a plane of the JJ, and providing no magnetic field in the plane of the JJ. An AC input signal (AC_SIGIN) applied at an input of the switch network configuration (12, 40, 60, 90, 130) is passed through to an output of the switch network configuration (12, 40, 60, 90, 130) in a first magnetic state, and substantially reflected back to the input of the switch network configuration (12, 40, 60, 90, 130) in a second magnetic state. The first magnetic state is one of inducing and not inducing a magnetic field in a plane of the JJ, and the second magnetic state is the other of inducing and not inducing a magnetic field in a plane of the JJ.