Superconductive Coaxial Filter Tuning via Magnetic Field
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Solution Overview
Problem
Conventional metal powder filters face challenges in tuning the cut-off and corner frequencies, often resulting in undesirable attenuation in the pass-band and insufficient attenuation in the stop-band, especially when operating at cryogenic temperatures, due to the limitations of normal metal powders.
Innovation Solution
The use of a dissipative matrix comprising superconductive materials, such as superconducting metals, oxides, and ceramics, which can be tuned by adjusting the energy gap frequency through external magnetic fields or by incorporating paramagnetic or ferromagnetic materials, allowing for precise control of the cut-off frequency and enhanced attenuation in the stop-band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If normal metal powder is used in the dissipative matrix, then the filter can operate at cryogenic temperatures, but the cut-off frequency cannot be tuned and attenuation in the pass-band increases
Solution Approach 1:
The patent applies parameter changes by transitioning from normal metal powder to superconducting material in the dissipative matrix. This material substitution fundamentally changes the electrical properties, enabling frequency-dependent attenuation characteristics that allow tuning of the cut-off frequency while maintaining low pass-band attenuation through the superconducting state's zero resistance property.
Solution Approach 2:
The patent employs composite materials by combining superconducting material with the dissipative matrix structure. This composite approach integrates the unique properties of superconductors (zero resistance below critical temperature) with the filtering functionality, creating a system that achieves both frequency selectivity and low loss in the pass-band.
2Loss of energy
If normal metal powder is used in the dissipative matrix, then the filter structure is simple, but attenuation in the stop-band is insufficient
Solution Approach 1:
The patent utilizes parameter changes by exploiting the critical temperature transition of superconducting materials. Below the critical temperature, the material exhibits zero resistance, creating a sharp cutoff frequency response that provides superior stop-band attenuation compared to normal metal powder, while maintaining a relatively simple coaxial filter structure.
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 the design of low-pass filters with desired cut-off frequencies between 1 GHz and 15 GHz, achieving less than 0.5 dB attenuation in the pass-band and more than 40 dB attenuation above 100 GHz, while maintaining low attenuation at cryogenic temperatures.
Implementation Method 1
the particles of the metal powder are conductive and together provide a very large surface area over which high frequency signals carried on the conductive wire are dissipated via skin-effect damping
Implementation Method 2
high frequency signals carried on the conductive wire are dissipated via skin-effect damping
Implementation Method 3
A superconducting material may generally only act as a superconductor if it is cooled below a critical temperature that is characteristic of the specific material in question
Implementation Method 4
by incorporating paramagnetic or ferromagnetic materials, allowing for precise control of the cut-off frequency
Implementation Method 5
by incorporating paramagnetic or ferromagnetic materials, allowing for precise control of the cut-off frequency
Data Source
AI summary
Adaptions and improvements to coaxial metal powder filters include distributing a dissipative matrix mixture comprising superconductive material, metal powder, epoxy, and/or magnetic material within a volume defined by an outer tubular conductor and inner conductor. The frequency response of the filter may be tuned by exploiting the energy gap frequency of superconductive material in the dissipative matrix. The inner surface of the outer tubular conductor may be covered with a superconductive material. For a dissipative matrix comprising magnetic material or superconductive powder particles of a certain size, an external magnetic field can be applied to tune the frequency response of the filter.