NFC Antenna Tuning 101
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- เผยแพร่เมื่อ 7 ส.ค. 2015
- We sit down with a set of NFC antennas and inlays to test them with a spectrum analyzer for proper tuning parameters. We discuss many of the variables that affect NFC reader performance and how best to avoid issues in the field. Understanding the concepts covered will help in buying the right NFC reader and tags for your project.
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Hi, can you share the link of the directional coupler you are using in the video?
Is it possible to have a 8-12mm RFID chip antenna read into a multi coupler antenna and then transmit RF through Software Defined Radio where the chip can amplify your own voice?
cool! what is the power splitter you're using for this frequency range?
Are you referring to the directional coupler mentioned at 5:29 time mark??
any tips on making a custom cylinder antenna that can read those fancy nfc implants? that will connect to an RC522 that is compatible with arduino.?
sure, there's plenty of insight on flomio.com/ask-the-flomies ... rule of thumb is 6 turns of 32 gauge wire
I have a question about the NFC metallic amplifier embedded in a credit card. Is that what it is? it doesn't seem to be the actual antenna for the chip. How does that work? is there a way to have one coil receive and then transmit to another coil that then talks to the NFC chip that has a built-in antenna? So like a coil extender? Thanks
What makes you think that it's not the actual antenna for the chip? Either way, there is the phenomenon of inductive coupling that you can leverage for coil extension. This is how our NFC Patch Kit product works (flomio.com/shop/readers/nfc-patch-kit/).
When tuning a tag antenna using the setup above, do you just connect the two leads of the tag antenna to the coupler?
Did you need to add any additional options to the scope in order to perform those measurements?
Is the connection from the directional coupler to the antenna a particular impedance?
The spectrum analyzer setup does not wire into the tag antenna. The two leads are from the proposed reader antenna coil and these plug into the directional coupler "IN" port. In order to perform the return loss measurement for antenna tuning you will need your spectrum analyzer to have a "Tracking Generator". This is basically a generated signal from the "OUT" port that the analyzer can track in the "IN" port (of the analyzer, that is). NFC transceivers generally come with a 50Ohm matching impedance so you need to set your antenna front end discrete component values to allow for that. There are several tools online that will assist your loop antenna design based on wire gauge, number of loops, and loop diameter to approximate a 50Ohm impedance and highest Q factor for NFC tags. Overall the common transceivers on the market are pretty tolerant to mismatches so you should be able to get something that works while not perfect.
Which SA are you using here?
The setup he has is a magnitude only Network analysis. If you have a vector Network analyzer you can do the same thing to measure the return loss. The spectrum analyzer he is using has a tracking generator to be able to perform that measurement. The measurement is limited by the directivity in the coupler. To design that magnetic antenna you can use the Biot-Savart law to be able to generate the proper geometry which is directly proportional to the reading range. I have designed these using HFSS and Sonnet EM to extract the antenna parasitic and ultimately a model RLC you can model in Keysight ADS.
Where's the actual antenna tuning part of the video?
The antennas were made by coiling 32 AWG wire with different loop counts and geometries. The Spectrum Analyzer then tells you which couples best with the target tag.
@@FlomioTV I was looking for a guide to adjust the tuning components between the coil and the reader chip, NXP's documentation being a bit vague of how to make the measurements. Hence I too was a little disappointed by the lack of tuning in this video.