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Material for "Shielding" RFID Tag

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daneloctober

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Hello! I'd just like to ask, if If you were to put an RFID Tag that is not for near-metal use on a metal surface, what material should you put between the metal and the tag to decrease the negative effects of the metal on the tag antenna?... Aside from putting some space between them, that is... THANKS!!!
 

enjunear

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Pretty much nothing is better than air. Materials with a higher permittivity will only increase the E-field strength inside the dielectric, making it appear more "conductive" at RF.
 

enjunear

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What material does Flexield use then?...
I haven't explored their offerings in-depth, but they appear to be lossy magnetic materials. I believe they are more meant to attenuate the potentially radiated fields. I'd guess that if you stuck something like their products to the back of your RFID, then you'd attenuate a lot of your desired signal.
 

daneloctober

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I think I'm gonna use glass... Simulations through HFSS show that it has the least de-tuning effect... at least according to the available cheap materials in the HFSS package...
 

FvM

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I think I'm gonna use glass
You didn't exactly tell, what "RFID Tag that is not for near-metal use" means in your case. I guess, you are still working an your previous 900 MHz topic. If it's an E-field antenna, e.g a dipole, only distance or "air", as enjunear told, will help. Plastic foam will be better than glass, and air is better than plastic foam. Preferably, a RFID tag should use an "one-sided" antenna in this situation, e.g a patch antenna.
 

daneloctober

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You didn't exactly tell, what "RFID Tag that is not for near-metal use" means in your case. I guess, you are still working an your previous 900 MHz topic. If it's an E-field antenna, e.g a dipole, only distance or "air", as enjunear told, will help. Plastic foam will be better than glass, and air is better than plastic foam. Preferably, a RFID tag should use an "one-sided" antenna in this situation, e.g a patch antenna.
Oh sorry. Hehe. It IS a patch antenna, and I'm supposed to determine materials that will be suitable to put between it and a vehicle plate (as in license plate). So I need something rigid. I've simulated glass, rubber, FR4, and polystyrene (using HFSS), and FR4 gave the best result. But it's the most expensive, so I chose glass because it's rigid and it's the 2nd best performer. =)
 

SherpaDoug

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How about designing a patch antenna to work WITH the license plate instead of fighting against it?
 
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FvM

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How about designing a patch antenna to work WITH the license plate instead of fighting against it?
I also expect, that a patch antena can perform well in this situation.
 

daneloctober

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How about designing a patch antenna to work WITH the license plate instead of fighting against it?
Well... We did think about that. But we figured it's going to take a lot of time, it would be a master's thesis at least.. I'm just an undergraduate student. hehe. But yeah, that would be a great idea.
 

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