Hi,
I don't have any experience in RF design but I need to design the matching circuit for this RFID antenna (PDF attached) to work with the ST25R100 (PDF also attached).
(NOTE: IF for some reason that antenna cannot be used, can you please suggest some other [ideally] rectangular antennas that can be used and that are FLEXI-PCB TYPE because we need to attach it to a curved plastic surface).
As long as the RFID card can be read reliably every time from a distance of at least 20mm, then it is acceptable.
I saw the reference design but the values are different. And after trying to play with the ST tuning tool I still don't know what values to put into some of the fields: https://eds.st.com/nfc-tuningcircuit/
From the datasheet, I assume the values to input in the software are as follows: antenna self resonance = 13.56MHz, DC Resistance 2,000mR and inductance 2,000nH. Correct?
BUT... These are not clear to me in the tool input fields:
- should I use series or parallel resistors? What are the pros/cons of each and the criteria for choosing?
- what is the Parallel Resistance (whether I click on series or parallel resistors it still shows PARALLEL Resistance)? How do I choose that value (it is not in the datasheet)?
- I can put the most extreme and different values in the Antenna input fields (top area) but it does not seem to solve, it always gives error of either Q being too high or Cp being less than 0?
Also, do we need to add two ultra low capacitance TVS for ESD protection between each of the two antenna pins and ground (or after the resistors) or would that de-tune it?
I would very much appreciate if you could please help me find the right values?
Thank you
