Monday, January 27, 2014

Designing an RFID antenna - part 1

Designing an RFID antenna:

Basically I am motivated to replace the antenna on this RFID reader. The reader is really cheap, and fits my porpoise, its recognized as a USB keyboard.

My Idea is to build a new antenna that can be fitted into a PVC tube and have a usb "reading rod".

Hackaday has provided me with some information about this, but nothing useful about antenna modding.

Thanks a friend (Chris) I manage to get some technical documents (such as this,  this, this) about this matter, some turned to be really useful and cover basic subject (like Magnetism, Faraday's Law, Mutual induction) it really help me understand more about RFID, it sure brought me memories when I was in college, but could not find any decisive information on how to shape a new antenna.

I know antenna shapes and geometry are dependent on: Frequency (125 Khz in this case) and range of reading (of the tags) and number of turns. Of course many other items, but they are purely derivative from the two I mentioned first.

So I disassembled my rfid reader:

Up to here all done, simple building, now I will desolder the coil antenna, saving it in case of reusing it or take it as a model.

Desoldering was easy, two points, done! You can see below the antenna saved for future.

Now the best part, with 20 meters of copper wire I am planning to do some coils, in order to check which confirations works best.

Three basic squares using push pins, will serve two make the coils and test them.

I have 3 configurations to test:
a)50mm x 60mm
b)40mm x 50mm
c)35mm x 120mm

Tune in for future results!


  1. Hi,
    Not sure what you are doing, but since we try to hack the same hardware, guess we should share knowledge.
    Here is my post -

    1. Also, so your site, NFC its usualky 13,56mhz (such as mifare tokens, bus passes, credit cards) v this particular reader is 125khz (very low freq, usually refered as rfid, plain)

      Have a good one, feel free to contact me.

  2. Thanks a lot for commentingg Shushu, I am just trying to explore into how to make a new coil antenna and how antenna area, radioa md size fit into the ecuation to have it tunned to 125khz.

    What are you planning to use it for? What OS are you going to use it ? I am having this problema t the moment

  3. I am happy to find your distinguished way of writing the post. Now you make it easy for me to understand and implement the concept. Thank you for the post. rfid tags