Is there are possible to let the ST25R95 reading distance be over 30cm?

[Lchan.1]

I am doing a project which requires ST25R95 reading distance operating about 30cm. I studied the EV kit of ST25R95 and implemented the circuit as a reference to design my system.Unfortuneately, the reading distance is still around 7cm. After several days of studying the AN5248 and tuning the STSW-ST25R003, I still can not get a breakthrough in a longer reading distance and better magnetic field performance. Is there any reference circuit design that I can study to enhance my design?

PS. VPS_TX is connected to 5V, it suppose output power at 230mW

reader antenna: Molex 1462360031

tag model: ST25TV-ESEAL

[Ulysses HERNIOSUS]

Hi LChan.1,

please see https://community.st.com/s/question/0D53W000006r47nSAA/st25r95-distance-range-output-power-inductor-as-antenna which should answer (most?) of your questions.

I think 30cm which the given antenna is really out of scope.

BR, Ulysses

[Lchan.1]

Thank you for answering my question. The link you provided did little help in finding a suitable antenna in my design. From the test report on (page 11)https://www.molex.com/pdm_docs/as/1462360001-AS.pdf

1462360031 could receive signal over 30cm. The NFC IC TRF7970 they use could merely output 200mV per reading cycle( ST25R95 could provide 230mV!!) Therefore, I thought ST25R95 could get a higher distance in my design but it seems I am still stuck in solving this problem.

[Ulysses HERNIOSUS · Accepted solution]

Hi,

I read figure 6.1.4 as reaching ~90mm (=9cm) distance with a 75*45mm tag. Interpolating the diagram between 75*44 and 38*22.5 tag antenna I would expect an operating range in the 7 to 8cm area.

Not sure where you are reading 30cm???

At such small antenna I also don't expect a major performance boost by further increasing the output power, especially not when going from max 200mW to max 230mW.

Best Regards, Ulysses

[Lchan.1]

oh, I think I made a huge mistake between mm and cm......

I think I should change another ic for my design.

Do you have any recommended NFC IC for about 30cm reading distance?

[Ulysses HERNIOSUS]

Hi Lchan.1,

I think for getting to 30cm reading distance you will need to significantly increase the antenna size.

As a rule of thumb the diameter of the antenna corresponds directly to the achievable read range (Good coupling conditions between reader and tag antenna, tag which works under low power (e.g. ST25TV), ....) .

So for 30cm read range I would expect an antenna of about 30cm.

For details you may want to study the literature, e.g. "RFID Handbook: Fundamentals and Applications in Contactless Smart Cards, Radio Frequency Identification and Near-Field Communication" by Klaus Finkenzeller.

Best Regards, Ulysses