I want to know measurement methods of microwave absorption/shielding effectivness in Anechoic Chamber
(i) X-band, 8.2 to 12.4 GHz
(ii) Ku-band, 12 to 18 GHz
I know about: Arc method where transmitting and receiving antenna are placed on Arc in front of DUT. In other method, DUT is placed between two horn antenna.
Dear Dr. Singh,
welcome,
If you want to measure the transmittance of a certain material or a complex of materials you can sense the electric field by kind of a loop antenna connected to low noise amplifier and then to peak detector which can calibrated to measure the field directly. Then removing the material and measure the field intensity. Then the transmittance will be (Ewith the material/ E without the material)^2
To measure the reflected wave from the surface of the material you need to tilt the the plane of the material such that the incidence and reflected waves have different directions and so you can sense the electric field of every one using the previous field probe. It is so that you measure the quantities as you define them.
Best wishes
normally you like to avoid doing such measurements in an anechoic chamber (the setup maybe quite heavy and not everyone has an installation of this kind) and you better try to this first in a coax or waveguide test setup..or with suitable probes on the material directly (limited range and precision)
Measuring material parameters for shielding/absorption in an anechoic chanber is difficult and simplistic transmission/reflection measurements can be misleading. You need to account for sample size effects such as edge diffraction and the effective beam size from your antennas at the sample. It's all basic physics. You could try coaxial waveguide techniques but sample edge connections to the waveguide can cause problems. Other techniques exist using absorbing materials to reduce the edge effects.
A considerable literature exists on this subject, Start by looking in IEEE Trans EMC.
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