Hi, We want to measure the radiation patterns of an implantable antenna. The mimicking gel that we are using has different conductivity than that used for simulations. We want to increase the conductivity of our mimicking gel without increasing the permittivity.
We know that adding sugar and salt will increase the conductivity. However, it decreases the permittivity!!!
Any suggestions?
I don't have an answer, but a warning. In microwaves and RF it is the refractive index that matters. The real part determines the wavelength and the imaginary part the losses. The refractive index is the square root of the relative permittivity - ignoring permeability. When you take the square root of the complex relative permittivity, it halves the angle of the complex number as well as taking the square root of its length, and the imaginary term in the permittivity, which will be changed by changing the conductivity, will result in the real part of the refractive index being changed. If you want the real part of the refractive index to be unchanged, it may be necessary that the real part of the permittivity falls a bit if the conductivity increases. It is worth working out the numbers for the real and imaginary refractive index you want and what permittivity that results in.
However, my warning may be redundant, because you already know what real and imaginary relative permittivity you want!
Have you tried carbon black (powder)?
Thank you Malcolm White for your replies
Yes, we have the right values of permittivity.
We didn't try carbon black. I will search for the permittivity and conductivity of carbon black at our frequency range of interest to see if it is a good choice!
When I was preparing my PhD, I remember guys on body-network project were using some kind of fertilizer, a green gel-like substance. That was funny, it looked more like agricultural department when they were mixing things. Surely, you will not find that Japanese thing around you, but what I want to say is that it requires some art of search and imagination; you can find the required compound in a very unexpected place.
Andrey Porokhnyuk Thank you.
As you mentioned maybe I will not find it here. However, I have a curious question to ask, do you know the exact name of that fertilizer? I want to check the electrical properties of that substance!
sorry, I didn't ask them. Maybe there is a mention in the papers of Y.Kado, or H. Shimasaki groups from K(yoto)IT.
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