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Crown Ferrite Enterprise Co. |
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EMI / RFI / Microwave Absorbers Flexible Absorbent Material (FAM) |
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PDF Version
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Application for RFID
/
NFC
on metal
: When RFID / NFC tag or RFID / NFC reader/writer attached on metal (PCB ground / metallized shielding surface / battery), the read distance will become much shorter than expect. The traditional design is to increase the space between RFID / NFC antenna and metal but cause the RFID / NFC device with a big thickness. FAM can be an anti-metal solution to improve the read distance for LF (125 / 134.2KHz) and HF (13.56MHz) bands. After insert FAM between RFID / NFC antenna and metal surface, the read distance can recover maximum 80% efficiency than the original distance with no metal. Due to FAM with small thickness, a slight figure can be designed easily than before. |
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Test Example for RFID Read
Distance (Reference)
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FAQ for RFID/NFC applications : |
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Q1 : Why FAM applicable frequency is GHz but can be used for for LF (125 / 134.2KHz) and HF (13.56MHz) ? A1 : FAM is a kind of high electrical resistivity and low magnetic loss material. It works well for suppression near-field electromagnetic coupling effects (RFID / NFC / Wirelss Power) because it’s power loss is low when frequency is under 10MHz.
Q2 : How RFID / NFC affect by metal? A2 : The magnetic flux from RFID / NFC tag or reader/writer will induce eddy current on metal surface and generate a reverse magnetic field to offset the magnetic flux to cancel the communication.
Q3 : How to use FAM for a RFID / NFC tag? A3 : Attach FAM with antenna / inlay tightly and embed into any shape as you need. When the tag attached on metal surface, please use FAM side, not antenna side.
Q4 : How to use FAM for a RFID / NFC reader/writer? A4 : Insert FAM between reader’s antenna area and circuit board tightly to get a compact design. When use the reader/writer, please don’t use antenna side to attach the metal surface.
Q5 : Can I use FAM for a UHF RFID tag? A5 : FAM is not suitable for UHF RFID tags.
Q6 : How to choose FAM thickness? A6 : FAM has standard thickness as page 8. You can test different thickness with your RFID / NFC device directly to compare which thickness can get the best distance. It's a fast and easy function to evaluate FAM.
Q7 : Why I can’t get a good read distance after using FAM? A7 : When FAM close RFID / NFC device, the inductance in LC circuit will increase and the response frequency will become lower. If your tag’s frequency is far away reader’s frequency, the read range will become shorter than before. In such a case, re-design the antenna to adjust L and C to get a reasonable response frequency will be the best function. (please see page 5)
Q8 : Is there any factors can change RFID / NFC tag read range? A8 : Many diverse factors will cause read range different, for example : operation frequency, reader output power, tag antenna size, reader antenna size, active tag or passive tag, reader position, objects interference, others RF device interference, metal material/size, FAM material/size and etc.
Q9 : What FAM dimension should I use? A9 : When FAM cover the whole RFID / NFC antenna area can get the best performance. (please see page 6)
Q10 : How is the performance if I assemble small piece FAM to cover the whole RFID / NFC antenna? A10 : The performance will the same the whole piece FAM.
Q11 : Is there any different for FAM two sides? A11 : FAM include soft rubber type absorber (FAM1/FAM3/FAM6) and flexible sintered ferrite sheet (FAM7/FAM9). FAM is a well mixed material with one single layer design so the two sides are the same. |
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The variation of response frequency when RFID tag + FAM + metal (Reference) :
1. The response frequency is become lower when FAM thickness become thick but the signal strength with little difference.
2. The response frequency is increase when metal attached, but the signal strength is smaller if FAM thickness is thinner. It means the metal affect more when FAM is thinner.
* The dimensions of FAM and metal are 85.6x54mm. * The RFID tag is standard ISO card size (85.6x54mm) with HF TI 2048 chip. |
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Test Example for RFID
Read Distance vs FAM dimension (Reference)
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* The test inlay is used for 85.6x54mm standard ISO card with antenna size 76x45mm. * Different reader, tag, metal material will cause different read distance. * As upon test result, the longer read distance can be get if FAM size and antenna size are the same. * If FAM or metal is bigger than antenna size, it will not cause read distance many different (as below figure).
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