RFID reader and antena
I am looking for solution modules for RFID. Specifically the RFID readers and appropriate antennas. I am working with a design that needs to follow the requirements listed below:
1) range between tag and antenna about 10-20cm
2) materials between tag and antenna:
~5cm wood plate,
~5-10cm polyurethane or polyester
3) possible some metal bolts in PU/PE
4) tag will have to be wristband
5) the antenna max size about A5 paper sheet
The position of tags may differ so perfect would be circular polarized antenna. The set will possibly work off-grid so would be nice to have something requiring less power. The tag will be connecting with very low frequency about 1 tag per 1-2 seconds.
I was hoping to find modules in low-frequency solutions. I am aware that distance of 10-20 cm may be a hard to get with LF/HF. I am also considering short-range UHF but the price of the module needs to be considered.
I would be grateful for your advice what module to chose.
Please let me know if there is anything else I need to clarify.
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hmm... Unfortunately, I can't give a exact module recommendation for your project, but maybe the following is helpful to find a solution:
One basic rule is that the distance is related to the reader antenna diameter, so bigger reader antenna means greater distance. However, a wristband tag antenna would be very small, you'll have to take that into account. So, I doubt that an A5 sized antenna will work, because with an antenna of that size, you'll might have a hole in the mid of the RFID field, which results in no energy for the tag.
Also the distance is affected by the used reader technology. ISO14443 is specified for 10-20cm, but this is for card sized tags - I doubt that you'll get this distance with a wristband tag antenna, especially for your 10cm requirement. It might be possible depending on the output power of the RFID reader chip.
ISO15693 might also be worth a try. ISO15693 has higher distance, because it's narrow-band compared to ISO14443. Both are working at 13.56MHz.
I don't know about distance for 125kHz RFID systems. Maybe it's also possible to have the antenna as a separate board from the reader, connected by coax cable - it depends on your requirements if this is possible.
You'll also have to take security requirements into account.
I think the best approach would be to confirm if ISO15693 is capable to fulfill your needs, then get some evaluation kits from chip manufacturers like ST or TI to make a proof of concept. Maybe you need additional tags in the right size for verification. Also check the provided software stacks for the reader chips if they can be smoothly adapted to your host controller IDE to get the software up and running in time.
With those requirements, I recommend to test the setup under real conditions as early as possible. Even if a evaluation kit might give the required results, you'll still might have to make your own antenna, which must be adjusted and tuned to the environment (the metal bolts mentioned by you might have an influence, for example). So, you'll need an impedance analyzer.
Have you considered the NFC Type-V tags/readers? They can go up to 1-2 meters, but with slower data rate (26kbps typically). If the reduced data data is not an issue, this can be a solution. The relevant standard is the ISO/IEC 15693 For instance, have a look at https://www.st.com/content/st_com/en/products/nfc/st25-nfc-rfid-tags-readers/st25-nfc-rfid-tags/st25tv-series-nfc-tags/st25tv04k-p.html