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ST25R3916 Discovery GUI - ST25R3916-DISCO (MB) v1.4.3, Tune Antenna issue

Ran-26
Visitor

‎2026-01-08 12:00 PM

Hello,

I currently working with the STEVAL-25R3916B kit and using the ST25R3916 GUI to tune the antenna. My goal is to achieve a target amplitude of 2600 mV or higher, but the system remains around 2 V even when 5 V is selected for RF power on the reader expansion board.
I’ve noticed that the amplitude displayed in the GUI is significantly lower than the target value after performing antenna tuning, and the parameter AAT_B reaches its maximum limit of 255.

Here are the outputs and screen copies.

-Startup Tab

ST25R3916 Reader Board Detected.. 'ST25R3916-DISCO (MB) v1.4.3' FW=1.4.3                             

Chip variant ST25R3916B                                                                               

ST25R3916-DISCO (MB) v1.4.3                                                                    

VDD: 4.937 V                                                                            

Tune antenna: AAT_A: 192, AAT_B: 255 (Measures 28 in 308ms)                              

Amplitude: 1.86186 Vpp(143), Phase: 113.188 °(87) .. f(amplitude, phase) = 68              

Ran26_0-1767902124651.png

 

-non-expert mode of the Antenna Features tab

Amplitude 1.85V (Target 2.3V)

Ran26_1-1767902166644.png

 

-Expert mode of the Antenna Features tab

Amplitude 1.84V (Target 2.3V)

Ran26_2-1767902202701.png

Thanks

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1 REPLY 1
Ulysses HERNIOSUS
ST Employee

‎2026-01-08 10:57 PM

Hi Ran-26,

AAT can only change the antenna matching within the limits given by the antenna, static matching and variable capacitor range. Also the measured amplitude is directly influenced by the capacitive voltage divider on the RFI pins.

Please refer to AN5276 and AN5322.

BR, Ulysses

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