Hello,
my name is michael and i am working on a project with the PN7160 with asymmetric antenna tuning.
At normal room temperature, the reader mode works very well at a range of up to 40-50mm without reading errors. But as soon as the temperature drops below 0°, communication (with the card) abruptly stops. Not only lower range but completely. However, the NFC field is still present (at 13.56MHz). When the temperature rises again, the whole thing starts to work again.
The problem is due to the temperature of the matching circuit or the PN7160, not the temperature of the antenna itself (tests with cooling spray).
The capacitors used are NP0/CG0, the inductors MLJ1608 chip inductors, all 0603.
Our antenna parameters:
1.76uH / 6.9pF / 720mOhm
Matchingcircuit (asymmetrical tuning):
We calculated these values with the formulas / NXP tools and get very good results (but only above 0°C):
160nH / 330pF, C1 = 56pF, C2 = 76pF, Rq = 3.3R.
(instead of 56pF/76pF we also tried with 60pF/80pF, with the same result).
We have also done a tuning by Smithchart. Interestingly, the whole thing seems to be quite detuned with the above values, but still works well.
If we then tune the matching to a more optimal Smithchart result, the function drops (range drops, read errors, tests at room temperature).
(C1 = 56pF, C2 = 60pF)
Is there something specific we should look into to find the problem in low temperatures?
Thanks in advance!
many greetings,
Michael
Hello Alb,
Please try the following:
Try to reduce the gain to 39dB or 32dB and check the performance.
See an example for Type A
BR
Tomas
