I would like to reflect EM waves (power density will be a few W per m2) at room temperature. The H field of the reflected wave should be inverted (shifted by 180 degrees), so the reflection has to be based mainly on magnetic dipoles, not on electric dipoles nor on conductivity; i. e. the relative permeability of the mirror should be considerably larger than its relative permittivity. There will be only a weak DC bias H field or none at all; the material will certainly not be saturated. S11 in the range from 0 dB to -3 dB would be great, but I guess something about -10 dB is more realistic.
Ferrite tiles would be fine but the datasheets usually assume that the purpose is absorption not reflection; so return loss is given for the case that the tiles are backed by a conducting sheet. Therefore the given return loss is partly caused by the superposition of the waves reflected from the ferrite and from the metal.
Do you know of a commercially available material well suited as a magnetic mirror in the frequency band mentioned above? I would greatly appreciate any hints, and, additionally, links to distributors!
Hi Soumit,
many thanks for your answer! However, if I'm not mistaken silicon carbide is diamagnetic, so the effect of its permittivity is larger than that of its permeability, and the reflected waves can be expected to have an inverted E field. But I need an inverted H field.
I am very sorry for the late reply dear Joerg Fricke,
firstly I admit, I was mistaken after knowing the fact that u want an inverted H field, in such case the retaining field strength of the material will be not so strong so better to use a high reflective mirror of dodecagonal ferrite oxide, or higher atomic nickel or manganese oxide. Reason is the return loss can be adjusted according to the engineered material permittivity which is possible in such artificial materials and u can bring down the S11 upto -5dB in such cases.
Dear Soumit Samadder Chaudhury,
thank you very much for your second answer! And of course, there isn't any reason for an apology! Your answer would help me even if it came after a week.
S11 of about -5 dB would be fine! Do you know of any company offering tiles of such materials?
Dear Mr. Fricke,
at my opinion you can use a silver layer with a thickness of 1 mm . Then you have a mirror material with a shielding effect of 100 dB for the E field.
All the best
F. Gräbner
Dear Dr. Gräbner,
many thanks for your hint! A silver mirror would certainly come closer to a perfect mirror than a ferrite mirror but I have a setup in mind where it is crucial that the impedance of the mirror is larger than that of air in order to invert the H field. If you know of a commercially available ferrite with permittivity as low as possible and permeability as high as possible, suitable for frequencies up to about 3 GHz, I would be grateful for every suggestion.
Best regards,
Joerg Fricke
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