Gas/Fluid Dielectric: Seeking EE Help for Variable Dielectric Constant

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Discussion Overview

The discussion revolves around finding a gas or fluid with a variable dielectric constant that can be adjusted physically, particularly through pressure changes, for use with microwaves in the 10-20 GHz range. The focus is on minimizing absorption and attenuation while maintaining control over the dielectric properties.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks a gas or fluid with a variable dielectric constant that can be altered by physical means, specifically through pressure changes.
  • Another participant inquires whether the desired effect is to control delay and asks about the polarization and confinement of the microwaves.
  • A participant expresses a preference for minimal attenuation and confirms that the microwaves are linearly polarized and will be confined in a vacuum space.
  • One participant suggests using an anisotropic dielectric material in a waveguide, proposing that rotating the material could change the effective dielectric constant as perceived by the microwaves, although they express uncertainty about the impact on polarization direction.
  • Another participant proposes utilizing the Kerr Effect to change the dielectric constant with an external electrical field and mentions the possibility of rotating the material relative to the microwaves' polarization.

Areas of Agreement / Disagreement

Participants present multiple competing views and approaches regarding the methods to achieve a variable dielectric constant, with no consensus reached on a specific solution or method.

Contextual Notes

Participants have not fully explored the implications of their proposed methods, and there are unresolved questions about the effects on polarization and the practical implementation of the suggested techniques.

tekness
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Hi!

First time poster seeking some EE help.

I'm looking for a gas or a fluid that has a dielectric constant that can be varied by some sort of means(physical).
Something in the area of changing the pressure. I will be sending microwaves in the 10-20Ghz range through this gas/fluid, so as little absorption is preferred.Any help is greatly appreciated.
 
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Are you wanting this effect in order to control the delay? Are the microwaves linearly polarized? Are they confined to a wave guide, or are they in free space?
 
Thank you for your reply.
I would like as little attenuation as possible. They are linearly polarized, will be confined and will pass through to a tube-ish medium from one point to another. Vacuum space.
 
I googled anisotropic dielectric constant microwave, and got some interesting hits. Here is a sample hit:

http://www.scientific.net/0-87849-947-4/207/

And here is the hit list:

http://www.google.com/search?source...ric+constant+microwave&btnG=Search&nochrome=1

You might be able to have a region in your waveguide where you have a cylinder of anisotropic dielectric material, with the long axis perpendicular to the tube. As you rotate the cylinder, that will change the effective dielectric constant as seen by the linearly polarized microwave EM as it propagates down the tube. Not sure if that will cause any rotation of the direction of polarization, though.

Not sure that's of much help, just thinking out loud.
 
You could make use of the Kerr Effect and change the dielectric constant with an external electrical field. You could do as Berkeman says and rotate it relative to your mircowaves polarization.
 

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