How is an anechoic chamber designed?

I have tried a search but not much info.
I'd like to know, how is an anechoic chamber designed? i presume the size of it relates to the frequency but what other factors need to be taken into account and what calculations have to be made when designing an anechoic chamber?

thanks

anechoic chamber new england

The complete design of an anechoic chamber is non trivial task. You should consider many aspects, not only electromagnetic. For instance, you need a perfectly horizontal floor: no inclination is ment to be present on the floor.

Anyway, the main points I would consider in the design are the dimensions of the chamber, that practically limit the FarField range, and the choice of the absorbing panel, that practically limit the NearField range.

One should also consider the scanning system: the scanning area impacts on the truncation error in NF measurements and therefore it limits the max angle of the radaition pattern in NF-FF trasformation (max u-v component in the visible region). Hence, Once chosen the band of interest, I would consider the worst case and I would estimate approximately the minimum area of scanning.

Many other aspects concerning the shielding, the slides, the connectors, the cables, the rotatory joints one should consider. But, I would consider them in a second phase of the designing, once.

Anechoic chamber

beetro

thanks for the prompt reply. so for example, if i wanted a chamber to measure between 1-2GHz, what would be the initial phase of designing such a chamber?

Re: Anechoic chamber

Find room to place the chamber?

Dimensioning the chamber on the basis of the target antennas and of the types of measuring (FF range, NF range, EMC meas. ), I guess, is the first task to accomplish.

1-2 Ghz is a very low frequency range...you'll need a lot of space!
Bye

Anechoic chamber

haha!
well 1-2GHz in FF is just an example

Re: Anechoic chamber

There are 2 key features of an anechoic chamber:

1) the walls are ~ non-reflective, so you can get a good approximation to free space when you are measuring antennas. For this you need absorber material on the wall, ceiling, and sometimes floor. It is hard to get this right, as a lot of the materials that are great for this give off poisonous gas when set on fire, so you have to follow some strict fire codes. Also, it helps a lot if you are only operating over a narrow band of frequencies, as the absorber design is much easier.

2) The whole room is shielded. That is, when you close the door, any RF energy outside of the room is greatly attenuated. That way, when you see an rf signal picked up by an antenna inside of the chamber, you are pretty sure it came from the box you are testing. For this you need metal walls and a special door that has metal gaskets on it. I have seen some people do a reasonable approximation to the shield room thing by using copper screen on all the surfaces.

Re: Anechoic chamber

Sometimes a metallic paper (like the one for food!) can be enough thin to electromagnetically isolate the chamber...obviously the hisgest is the conductivity the lowest is the penetration depth. In a good anechoic chamber there is usually a metallic (silver) paper between the back of the panels and the actual shielding to improve the isolation.

Concerning the panels u can find online a lot of vendors. One of the best is Emerson & Cuming.

Bye

Anechoic chamber

for a tapered chamber, how would you define the taper angle?

Thanks for the replies

Anechoic chamber

I am also looking for some Anechoic design guideline. Here is a good book. IF somebody can upload

https://eu.wiley.com/WileyCDA/WileyTitle/productCd-0471208108,miniSiteCd-IEEE2.html