Superconducting Bias-Tee Circuits Without Large Inductors

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Solution Overview

Problem

Existing superconducting devices used for combining and separating direct currents and microwave signals require large inductances, which are technologically challenging to realize, occupy significant space, and introduce signal loss.

Innovation Solution

The development of on-chip superconducting circuits that include bandstop and bandpass filters, as well as quarter-wavelength transmission lines shunted by capacitors, to facilitate the combination and separation of direct currents and microwave signals without the need for large inductances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If large inductance is used in bias-tees for combining and separating direct currents and microwave signals, then the device can function as required, but the device occupies large space and introduces signal loss

Engineering Contradiction:

Improvesignal lossVSAvoiddevice space

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent changes the electrical parameters of the circuit by using quarter-wavelength transmission lines with specific characteristic impedances (e.g., 50 ohms, 265 ohms) to replace large inductance values. This parameter transformation allows the circuit to achieve the same filtering function with compact dimensions, reducing both space occupation and signal loss while maintaining the bias-tee functionality for combining and separating DC and microwave signals.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If large inductance is used in bias-tees, then the device can combine and separate direct currents and microwave signals, but the inductance is technologically difficult to realize

Engineering Contradiction:

Improvecombiner/separator functionalityVSAvoidinductance realization

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent substitutes mechanical inductance elements with electromagnetic resonance structures based on quarter-wavelength transmission lines. Instead of using physical inductors with large inductance values that are difficult to fabricate, the invention uses transmission line resonators whose electrical length (quarter-wavelength) and characteristic impedance determine the circuit behavior. This substitution makes the device much easier to manufacture using standard PCB or microwave substrate fabrication techniques.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If traditional bias-tees are used, then direct current and microwave signal combination/separation is achieved, but the device cannot be easily integrated on-chip

Engineering Contradiction:

Improvecombiner/separator functionalityVSAvoidon-chip integration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent transitions from a three-dimensional bulky inductor-based bias-tee to a planar two-dimensional transmission line implementation. The quarter-wavelength transmission lines can be laid out flat on a substrate, allowing the entire bias-tee circuit to be integrated directly on microwave chips or PCBs. This dimensional change enables compact on-chip integration while preserving the DC blocking and microwave passing functionality through proper impedance matching and resonance design.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 allows for the realization of efficient on-chip superconducting devices that reduce inductance, improve microwave bandwidth, and increase isolation between direct current and microwave ports, enabling both narrowband and wideband communication while minimizing signal loss.

Implementation Method 1

a first quarter-wavelength transmission line shunted by a first capacitor

Methodology Applied

Scientific EffectElectromagnetic resonance: Resonance

Implementation Method 2

A superconducting device is a device that can provide zero electrical resistance below a defined temperature

Methodology Applied

Scientific EffectSuperconductivity: Superconductivity

Implementation Method 3

The direct current circuit can comprise a bandstop circuit

Methodology Applied

Scientific EffectElectromagnetic filtering: Filter (electronic)

Implementation Method 4

The microwave circuit can comprise a bandpass circuit

Methodology Applied

Scientific EffectElectromagnetic filtering: Filter (electronic)

Data Source

PatentUS12148974B2Fabrication of superconducting devices that control direct currents and microwave signals

Publication Date: 2024.11.19 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Fabrication of superconducting devices that combine or separate direct currents and microwave signals is provided. A method can comprise forming a direct current circuit that supports a direct current, a microwave circuit that supports a microwave signal, and a common circuit that supports the direct current and the microwave signal. The method can also comprise operatively coupling a first end of the direct current circuit and a first end of the microwave circuit to a first end of the common circuit. The direct current circuit can comprise a bandstop circuit and the microwave circuit can comprise a capacitor. Alternatively, the direct current circuit can comprise a bandstop circuit and the microwave circuit can comprise a bandpass circuit. Alternatively, the microwave circuit can comprise a capacitor and the direct current circuit can comprise one or more quarter-wavelength transmission lines.