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I've designed a base board for a Velleman VMA405 (13.56 MHz) RFID reader based on MFRC522 IC. But, due to interference from the base board (I'm assuming the oscillator), the reading range is limited to a few millimeters instead of a few centimeters. I'm in talk with a company that specializes in RF shielding and they offered me a few tapes that I can use to isolate the reader. But I don't know which one to choose.

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My question is what materials can shield one side of the coil on the reader so that the base board does not interfere with the operation of the reader? Will this product provide the shielding I require?

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    \$\begingroup\$ Are you sure the cause is interference and not a badly matched antenna? \$\endgroup\$
    – Rev
    May 17, 2018 at 6:32
  • \$\begingroup\$ Yes. Because if I lift the reader of the board it works great. Here's a picture imgur.com/Pak6bgU \$\endgroup\$ May 17, 2018 at 6:36

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Note that RFID works with a magnetic field. The antennas are basically a pair of (magnetically) coupled inductors.

The shielding materials usually only block the electrical field and not the magnetic field. It is still possible that the shielding will work though, you will just have to try.

If the shielding does not work you could try shielding with a sheet of metal which does block the magnetic field. If a permanent magnet sticks to a piece of metal then that metal will do the job. For example: copper is non-magnetic and will not work. Steel is magnetic and will work.

The close proximity of the (magnetic) shield might prevent the RFID antennas from working as it influences their inductance and therefore the resonance frequency of the antenna + RFID circuit. Then you want a solution without using a shield. What I would then suggest is keeping the tracks with the (clock) signals on your PCB as far away as possible from the antenna. Also make the loops small because a long track/loop (signals always travel in loops, they go back through the common ground!) will radiate a magnetic field like a loop antenna. You might have to design a new PCB to include all these changes!

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