ST25R95: What impedance should the antenna be tunned to (16, 27 or 50Ohm)?

[MNosz.1]

Hi,

According to the datasheet, the differential impedance between TX1 and TX2 is 27Ohm for 3.3V and 16Ohm for 5V. For the version without EMI filter the matching criteria should: input impedance of the maching circuit is eqault to ST25R95 differential impedance. But in the spreasheet "ST25R95 EMI FILTER CALCULATION" the default value of the RIN cell the is 50Ohm.

What impedance should I tune the antenna to? If I use the VNA to measure the matching circuit with the antenna should I get 27Ohm or 50Ohm?

[Ulysses HERNIOSUS · Accepted solution]

Hi MNosz.1,

did you read AN5248. Its chapter 5.2 discusses choosing the right impedance.

Regards, Ulysses