Large / custom sized nfc tags?

[shanehill00]

Currently, I am doing research, assessing feasibility and building a prototype of an NFC based product.

I am discovering that the form factor for commonly available NFC tags are not going to meet my needs. So I need to start looking at something custom.

I am not an expert in the NFC field and I am still in early stages of research but I am quite serious about getting this done. Also, I have made prototypes that do work but like I mentioned above, the commonly available tags will not meet my form factor requirements.

The basic parameters of my needs are as follows:

1) Need to be able to operate on carbon fiber and metal (ferrite backed tags work in my testing/prototypes)

2) I need the tag/antenna to operate over a large field. I am currently working with the idea of antennas at 45mm x 100mm. I have used the online inductance tool ST provides to get a design that might work: eds.st.com/antenna/#/ but I know very little about antenna design and testing.

Can someone help me understand how I would go about getting tags that fit the above requirements?

[Henry Crane · Accepted solution]

Hello,

sorry for the delayed answer. I suggest you the reading og our application notes AN2866 (https://www.st.com/resource/en/application_note/an2866-how-to-design-a-1356-mhz-customized-antenna-for-st25-nfc--rfid-tags-stmicroelectronics.pdf) and AN2972 (https://www.st.com/resource/en/application_note/an2972-how-to-design-an-antenna-for-dynamic-nfc-tags-stmicroelectronics.pdf) dealing with antenna design and measurements basics.

if you plan to stuck you tag on metal, using ferrite sheet is mandatory. if using a spacer of 1-2cm is acceptable between tag and metal, use of ferrite may be not necessary if you accept to lose a bit in performance.

Our online tool is made to simulate antennas on material with relative magnetic permeability=1. Your ferrite material will strongly increase the equivalent inductance compared to the value calculated with our tool. This increase will depend on the ferrite material characteristics.

A strategy could be to calculate the antenna with our online tool, manufacture it on a thin PCB for instance and measure its inductance in free air and stuck on you selected ferrite sheet. Afterwards, you'll be able to redesign your antenna with our tool, anticipating the inductance multiplication factor due to the ferrite, based on the previous measurements.

Feel free to contact us for more details if necessary.

best regards,

Henry Crane RFID/NFC application engineer

[shanehill00]

Thank you for the response. Much appreciated! I will read the docs and reach out with any questions.