Superconducting Microwave Circuit Active Termination
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Solution Overview
Problem
Superconducting microwave circuits face signal reflections due to impedance mismatches between room temperature and cryogenic environments, leading to power dissipation issues and reduced operating margins, as conventional termination methods fail to seamlessly match impedance across transitions.
Innovation Solution
A microwave circuit with a compensation signal generator that produces a signal equal and opposite to reflections, canceling them out and ensuring distortion-free signal propagation by adjusting phase and amplitude, thereby mitigating the effects of discontinuities in the circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If termination resistors are placed in the cold space to terminate multiple transmission lines, then signal reflections are reduced, but power dissipation in the cold space increases significantly
Solution Approach 1:
The termination resistors are extracted from the cold space and placed in the warm space, separating the signal termination function from the cryogenic environment. This allows signal reflections to be minimized while avoiding the excessive power dissipation that would occur if multiple resistors remained in the cold space.
Solution Approach 2:
A single termination resistor in the warm space acts as an intermediary to terminate all transmitted signals. The signal paths are designed to converge to this single termination point, allowing proper signal termination without requiring multiple resistors in the cold space.
2Loss of energy
If a single output termination resistor is placed in room temperature, then power dissipation in cold space is reduced, but signal reflections increase due to impedance mismatches
Solution Approach 1:
The circuit topology is designed to dynamically adapt the impedance transformation through the signal paths. The splitter and combiner networks are configured to provide proper impedance matching at each stage, allowing a single warm-space termination resistor to effectively terminate multiple cold-space transmission lines without causing reflections.
Solution Approach 2:
The impedance parameters are transformed through the signal conditioning circuits. The splitter divides the input signal while transforming impedance, and the combiner recombines signals while maintaining proper impedance matching, allowing the warm-space termination to be effective for cold-space transmission lines.
3Reliability
If multiple termination resistors are used in cold space, then each transmission line is properly terminated, but the complexity of the cryogenic system increases
Solution Approach 1:
The termination function is extracted from the cold space environment and consolidated into a single component in the warm space. This eliminates the need for multiple termination resistors in the cryogenic environment, reducing system complexity while maintaining proper signal termination.
Solution Approach 2:
Multiple termination functions are merged into a single termination resistor in the warm space. The signal paths from multiple cold-space transmission lines are routed to converge at this single termination point, combining multiple termination requirements into one component.
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 significantly reduces signal reflections and maintains high operating margins in superconducting circuits by ensuring perfect traveling waves, even with multiple discontinuities, as long as the RQL circuit region has no discontinuities, thus optimizing power usage and circuit performance.
Implementation Method 1
A microwave circuit with a compensation signal generator that produces a signal equal and opposite to reflections, canceling them out and ensuring distortion-free signal propagation
Implementation Method 2
superconducting circuits residing in superconducting cooled cryogenic temperatures (e.g., 4°K)
Data Source
Figure 1~2
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AI summary
A microwave circuit (50) is provided that comprises a plurality of transmission lines (60) each configured to receive and propagate a respective waveform signal of a plurality of waveform signals, and a combiner (58) that receives and combines the plurality of waveform signals from outputs of the plurality of transmission lines (60) into a combined output waveform signal that is output terminated by an output termination resistor (RTOUT). The microwave circuit further comprises a compensation signal generator (VCOMP) that generates a compensation signal to mitigate reflections associated with the transmission of signals through the microwave circuit (50).