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

MNosz.1
Associate

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?

1 ACCEPTED SOLUTION

Accepted Solutions
Ulysses HERNIOSUS
ST Employee

Hi MNosz.1,

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

Regards, Ulysses

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1 REPLY 1
Ulysses HERNIOSUS
ST Employee

Hi MNosz.1,

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

Regards, Ulysses