RF transparent materials are materials where RF fields can penetrate with no heating happen. So far, I know some like Teflon, PPL, PVC, and ABS. They are made of plastics and have almost 0 dielectric loss factor. Anybody can suggest and give opinion about this.
Hi,
I could not infer what you are looking for from your question, but there are materials which are electrically conductive and RF transparent. An example of which is Germanium coated MLI used for antenna sunshields and which provide ESD protection (in case of antennas made of dielectric materials) as well as protection against sun radiations.
Kind regards,
Patrick
To Denis, I really do not understand this comment. A dielectric is by definition an electrical insulator...
The RF wave can propagate through the dielectric medium, the following is the list of dielectric medium through which the RF wave can propagate.
material Permitivity
Vacuum 1
Water (distill) 30-88 (depending on temperature)
Glycerin 42.5
Mica 3-6
Mylar 3.1
Neoprene 6.70
Plexiglas 3.40
Polyethylene 2.25
Polyvinyl chloride 3.18
Glass 3.7-10
PTFE (Teflon) 2.1
Polyethylene (PE) 2.25
Polyimide 3.4
Polypropylene 2.2-2.36
Polystyrene 2.4-2.7
Titanium dioxide 86-173
Strontium titanate 310
Barium strontium titanate 500
Barium titanate 1250 – 10,000 (depending on temperature)
Conjugated polymers 1.8 up to 100,000 (depending on type)
Calcium copper titanate >250,000
Dear Mr Macana, In RF terminology I think you are referring to radomes. Which allow unrestricted RF energy while physically protecting antennas, especially radar and avionics equipment antennas. The most common type is made by application of special resins on E or S glass fabrics. The resins are combination of some of the materials mentioned by Mr Mulla. But they do have a frequency response, at higher frequencies attenuation tends to increase for basic fabric/resin radomes. For higher frequencies usually glass based materials are used. Besides attenuation and heating deviation in the path of energy flow is also a measure of transparency of the material.
I want to add to the list Sajeed Mulla:
Styrofoam 1.02 - 1.06.
https://en.wikipedia.org/wiki/Relative_permittivity
Kind regards
Plain and simple, Styrofoam. Some of them have traces of carbon inside, other than that they are practically solid air.
I think Styrofoam is easily get burn in times of arcing. For me, the best RF transparent material is Teflon which can handle high temperature. Polypropylene is good also but not in the long run. Combination of the two could be better.
As Denis said, there is no such thing as a zero-loss dielectric. Vacuum is zero loss, everything else has some loss. Either there is some conductivity, or the electric or magnetic fields drag atoms about a bit and generate some heat. The loss tangent for ptfe is about 0.00015, which means it loses about 0.01 dB per wavelength as it travels. This isn't much, but it is about 1/4% drop in power for every wavelength, which isn't lossless. Dielectric losses are a significant part of the losses in coaxial cable and microstrip, whether it is ptfe, polythene, polypropylene, or something else.
ptfe gets soft at high temperature, and has a change of structure above room temperature that can make it problematic to use. If you solder the end of a cable with ptfe filling, and get too much of it hot, the ptfe pushes out of the end.
A nice example of a really VERY transparent material is high purity quartz as used in optical fibers..there we are now in certain wavelength in the ballpark of 0.1 to0.2 dB/km or similar.The basic idea which finally made it to the Nobel prize (since dielectric waveguides are known sine about 100 years) was to really push the push the purity of the qurtz glass to get from 3 dB/meter inititally to something like 3 dB/10 km. And in the optical range there MANY wavelength per km in such dielectric waveguide.
Hi, first I understood you might be interested in Radomes etc... but from the other contributions I understand your interest goes beyond... A colleague of mine suggested the following book regarding E fields / dielectric penetration. Hope it helps. BR. Patrick
Electric Fields in Composite Dielectrics and their Applications (Power Systems). Tadasu Takuma, Springer - ISBN: 9048193915
The totally trasparent materials are those who impedance is almost the same than air, so relative dielectric coefficient must be as close to 1 as possible (sqrt(mu/Er)).
Perhaps this paper helps you a little:
Calculation of effective permittivity, permeability, and surface impedance of negative-refraction photonic crystals, Zhaolin Lu
It depends whether you think glass is transparent to light or not. If that is your definition then materials with refractive index significantly higher than 1 and with some loss also count as transparent.
Dear Roland
We plan to place frequency modulator in a IP 67 enclosure to enable outdoor application trials. Would you kindly advise best material the enclosure thus there is no loss of the wavelength generated please.
Frequency range is 10 - 65Khz with 110 - 115dB.
Many thanks for your assitance.
Polypropylene, nylon, polycarbonate, polythere, PVC. Don't choose a plastic with carbon filler in it - which is used as UV protection but can introduce electrical loss.
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