Looking for EMI Shielding Product

[soaringeagle]

Hi ,

I am looking for EMI shielding products. I have visited the webistes of 3M and Laird Technologies etc. Their EMI absorbing material also comes in the form of (adhesive )sheets that are really thin and can be pasted right on the radiating strip ( i.e. Mircrostrip line ). But I want to know if any you members in this groups have an experience of using that sort of materials to limit the radiation caused by the microstrip line.I am curious if that will change the impedance of microstrip line or not ? If yes, then how can I avoid that ?

Thanks in advance for responding to my queries.

 

[jiripolivka]

If you do not put the absorbers directly on the microstrip, there will be no change of line impedance. To use the absorber as an attenuator or termination, it is usually cut into triangles to match line impedance.

EMI shielding means that one wants to avoid stray radiation from a microstrip line. Then the absorbing layer is applied to enclosure openings or slits. LImiting EMI should not affect the line function but only the stray radiation.

 

[FvM]

I don't believe that it's a good idea to place absorbing material on a microstrip. As any open TL structure, it couples to the free field and radiates a certain amount of the transported energy. Placing an absorber near to the microstrip will increase it's losses, but not necessarily reduce radiation.

Placing a shield with tight connection to the ground plane would be the preferred means. Absorbers can help to reduce standing waves in the enclosure and radiations through openings, as suggested.

 

[soaringeagle]

Dear FvM ,

I am attaching geometry of my problem.Please suggest me some solution. I have searched a lot on it but I have not yet reached at any solution.

My substrate , slot and feedline position has been clearly shown in the geometry. I have to put electronic equipment inside this box , that is why I want shielding of microstrip line without affecting the other necessary parameters.

Top side of substrate is also acting as ground for the microstrip line , according to the basic theory of slot antennas. Slot is wrapped around and is closing itself on the substrate in the form of a ring.