ST25R3918 Increase TX power through DPO

[ChintaN1]

Hello Support team,

We are working on the ST25R3916 NFC-based device and we are getting a lower range for passive tag type 5 is around ~10mm. So, we want to increase the detection range through.

Is it possible to increase the NFC tag detection range through the DPO feature?

If you have any reference code or document then please provide us.

Thanks & Regards,

Chintan Patel

[Ulysses HERNIOSUS]

Hi Chintan,

using DPO one can decrease the output power for cases where field in close distance is above the limits. Typically our applications are running at full power anyhow and you cannot increase this way the output power.

Which range are you targeting? What are the sizes of the reader and tag antenna?

Best Regards, Ulysses

[ChintaN1]

Thanks for your support.

The antenna size is 1cm x 1cm.

We are targeting a range 4cm from the antenna.

As discussed with our hardware team, they suggested for changing the NFC circuitry.

Thanks

[Travis Palmer · Accepted solution]

Hello Chintan,

Which device are you using? In the headline the ST25R33918 is stated, in your question talking about the ST25R33916.

Please be aware that the ST25R3918 is the low cost and low power variant of the ST25R3916.

Achieving 4cm read range is in general not a problem, but it also depends on the used tag antenna (size and q-factor) and surrounding environment. Metal close by (also PCB copper) can have a very negative influence on the NFC antenna and resulting magnetic field. 

If possible, I recommend to increase the antenna size. You should also optimize the reader antenna Q-factor (mainly by increasing the antenna-track width). For ISO15693 you can go quite high.

The matching impedance plays an important role to specify the output power of the ST25R devices.

Further details of the above mentioned optimizations can be found in this application note:

https://www.st.com/resource/en/application_note/an5276-antenna-design-for-st25r391616b-st25r391717b-st25r3918-st25r3919b-and-st25r392020b-devices-stmicroelectronics.pdf

Please let us know, if you have more specific questions about AN5276 and if you have been able to achieve your goal.

BR Travis