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Faraday cage design and parameters

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PaoloDellaVedova

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Hello guys,

I need to shild my lab equipment from the radiation emitted by an antenna.
The antenna emits signal in the freq range 2-4 GHz at power of few Watt.
Could you help me out in designing a suitable faraday cage??
I need specifications for dimensiona and materials..
Thank you very much
 

The Faraday cage should be made as an enclosed conductive-wall room. You do not define the size you need for the instruments inside. Do you assume a person inside?
The Faraday cage can be made of one-layer perforated conductive walls. The hole size for 2.45 GHz can be made < 1 cm as a cut-off waveguide. The door should be provided with tight conducting strips to ensure a good uninterrupted contact along the sides. All AC power and signal connectors should be provided with blocking/filtering devices that should suppress the 2.45 GHz signal by > 90 dB.
Designing such cage is not an easy project. It is better to contact your local government or university operating an anechoic chamber for EMS testing, and rent it for the time needed for your tests.
There are companies , e.g. ETS Lindgren and others, offering commercial Faraday cages.
 
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    Abeer_h

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Ehehehe, thank you very much! but i think I have to provide some more information...
So, i need to lock a small antenna into the faraday cage and shild that one from everything else. The antenna is circular loop 1cm in diameter and is placed on top of a normal microscope glass (76x26 mm).
The microscope slit and the antenna is placed in a microscope and I would like the cage to wrap JUST the microscope glass and the antenna..
Is it now little more clear about the dimension of my system??
sorry that i didn´t specify this at the beginning...
 

For such small case, ETS LIndgren offers small screened boxes to contain e.g. a cell phone, etc. Some companies are also renting such screened boxes.

To make your experiment serious and get qualified results, the best way still can be to coordinate with an entity with a standard anechoic chamber and equipment. Starting from scratch can be costly and the results not reliable.
 

To help get an idea of what you are doing you are observing a sample and its behavior under RF excitation.

I think the size you want will be too small. if you put a box around your antenna to allow the microscope to be outside the box the box will have a large influence on the fields generated by your antenna. This may obscure your results. Furthermore I would be cautious putting your eye so close to it (as in putting our eye to the microscope) when it is operating in this configuration. Containing the fields like that and then putting an orifice in the box to see it with a microscope could create a situation were there is more energy going into your eye then you would like from a safety standpoint.

To do what I have assumed you are doing I would suggest if you cannot get into a chamber get a broken microwave oven (as in you could get one cheap) and a microscope with a camera attachment. Cut a hole in the side for your cables and use a camera for your observations. Get a role of copper tape and tape around the cable/hole interface. You may also want to get some RF absorber material to line the insides of the microwave box to help suppress any cavity modes that could be set up.
 

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