Hello,
I am writing this post because I have encountered a strange behavior of the NT3H2211 chip for generating second- and fourth-order harmonics with respect to the fundamental frequency (13.56 MH
Specifically, I am working on an architecture of two custom PCBs that communicate via NFC.
One of these PCBs houses a non-NXP reader and has a related tuned antenna with a matching circuit. The other houses the NXP chip in question.
The behavior I observe is related, as I said, to the generation of spurious harmonics.
Specifically using the setup shown in the following image:
Using the same reader (with the very same register's configuration) and different passive chips I notice different behaviors. To detect these behaviors I am using a spectrum analyzer with corresponding antenna.
The attached images are the results of NFC communication between the reader with:
a) a generic NFC badge
b) generic NFC tag
c) custom PCB with NT3H2211 chip
d) OM23221ARD evaluation board
In a nutshell, it seems that the generation of second and fourth harmonics is the responsibility of the passive tag.
We can also rule out the possibility that this behavior is due to abnormal behavior of other ICs since the board hosting the passive tag is not powered during NFC communication.
Any inappropiate choice of antenna tuning components is also averted by the identical results produced by your evaluation kit.
I am really not sure on how to solve this issue. Would you mind helping me with this?
Hi,
NTAG I2C Plus has been tested for FCC and ETSI (using OM5569) according to EC Declaration of Conformity for OM5569/NT322E. Some harmonics may be expected, but below the limits.
Perhaps you could consider the following to try to filter them:
C1 and C2 are connected to GND, and their value should be around 12-22pF; Cp value would need to be adjusted accordingly/as needed.
Regards,
Eduardo.
