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antenna design of a a RFID reader

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sukanya

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antenna design

Hi,
I am designing a RFID reader. Can somebody help me with the antenna design of radio frequency applications. The reader works on frequency of 135kHz and the current ratings of the antenna should be 137mA. Please let me know as to how is the antenna to be designed and what are the different types of antenna that can be designed. Also tell me about the antenna that can be built on PCB.
Thank you.
 

Re: antenna design

It will be very difficult to construct the antenna on pcb at this freq. The antenna should be part of resonant circuit tuned at 125khz. BTW, for RFID, as far as I know, freq. is 125khz, not 135. The antenna should have the approximate area of a credit card, and the number of turns should be around 30. Wire diameter : 0.3-0.5mm. As I said before, the antenna should be a part of a resonant circuit, and in order to achieve maximum reading distance (U can obtain 12-15cm), you will have to tune the antenna by inserting/cutting turns untill you obtain a maximum voltage at its ends (>50Vpk-pk).

/pisoiu
 

Re: antenna design

Hi Sukanya

Pisoiu is quite right.Only with the higher freq. rf-tags,can you get away with a pcb-trace antenna design.

Check this link out.The first coupla pages advertise their product,but the rest goes into great detail on 125khz rfid antenna design.
**broken link removed**

Cheers
Raticus
 

Re: antenna design

At this frequency the physical range is very small and the coupling is inductive. Generally, the physical range is about the diameter of the smaller of the two coils (reader and responder) except for some exceptional cases.

I have seen a one meter range reader that had a transmitter coil a half meter across and a receiving coil about 6 cm square with many turns. Both of these were printed using thick copper to reduce the losses. The responders had fine wire wound many turns wound around the circumference of a plastic card (a mm or two from the actual outer edge of the card) a few cm across each direction with an IC connected to the coil.
 

Re: antenna design

yes, It are a lot of product running at this frequncy but at a reading distance shorter tahn 100cm. you may chose the product on 13.65Mhz
 

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