RFID Antennas

In the process of imagining potential IoT RFID devices, I’ve been looking more closely at how RFID antennas are deployed (for reader and writer devices). Here are a few examples, and a source document to aid in design.

First, the commercial LF reader. This is a pretty beefy antenna, surprising that it still only gets a few cm of range. This is from a medium-range ProxPro 5355 reader.

Next is the RFID-RF522 which I posted about earlier this week. This is an HF reader, which allows the antenna to be much smaller (because the wavelength is much smaller) — small enough to be printed on the PCB itself, which lends itself well to IOT design, especially #badgelife.

Now let’s look at the Proxmark3 RDV4. Without looking, I had assumed they managed to get an LF antenna implemented on the PCB itself, but I was wrong. It’s another wire coil antenna, it’s just sandwiched between the HF antenna (printed on both sides of the larger PCB) and the other PCB.

Then I found this interesting piece — an RFID emulator circuit from kukata86.com (note: Website is dated and SLOW). I say it’s interesting because this person apparently implemented a cloning card that is programmable and passive, meaning it doesn’t require battery for emulation. Also, he seems to have managed to get a LF PCB antenna into production. It takes up a good amount of board space, which makes sense, but if you can print it, you can run the calculations and get the right capacitor(s) to tune it to become resonant. Even though this was made a few years ago, it’s interesting. I just wish they provided KiCAD or Eagle files, or Gerbers, rather than just PDFs.

Finally, here’s a PDF tutorial on HF antenna design, for those who are interested in digging much, much deeper.

RFID_antennas