PN5180 antenna ITVDD to low

[BerndFiebig]

We have a custom reader with PN5180 and properly tuned antenna with Z=18 Ohm according to VNA.
The DPC_CONFIG Register is 0xF9 so that UTVDD is 5 V.
We have a continuous field with the strength of 6 V at a distance of 3 cm.
With this values, the ITVDD should be 261 mA.
With different values of DPC_CONFIG, ITVDD is linear to UTVDD. With a Z of 25 Ohm ITVDD should be minimum 200 mA.
However the current measurement ITVDD, under different loading conditions, is always less than 120 mA.
What could be the reason for this?

[danielchen]

Hi Bernd:

Do you have a smith chart for this issue?

Regards

Daniel

[BerndFiebig]

[BerndFiebig]

We use card simulation and reader mode.

For this reason the smith diagram is generated with a 10 Ohm resistor between ANT1 and ANT2.

What Z value should we vote for then?