RF430FRL152HEVM: Communication distance difference between power over RF mode and USB mode.

Hello Takashi-san,

Given the tag is USB powered so there is no concern about the RF field powering the tag, then what it sounds like to me is that the RF field at the limit of the read range becomes too small for either A) the tag to register the command sent to it, or B) as you stated, for the tag to be able to load modulate the RF field in a manner that the reader can recognize the response.

In either case, increasing the antenna size should help with this as it would improve the coupling between the tag coil and reader coil, thereby increasing the power transferred and offering a stronger signal.

However, I must forewarn that I have doubts only increasing the coil size will be sufficient to reach a read distance of 50 cm or more. Increasing the coil size would need to improve performance by 50% with the same output power and that sounds to me difficult to achieve.

Lastly I want to leave these comments for your understanding: The device you are using, while it is ISO15693 compliant in terms of protocol, was never intended to be used at such large read ranges. All practical applications we envisioned were for 10cm or less, and no testing occurred to determine the performance at extreme ranges such as 30-50 cm. If you find that the device is not able to meet your requirement for 50 cm read range then the only options will be to either reduce the requirement (which is exceptionally high from all my NFC experience...) or select a different tag which may offer better performance (you may find better performance with static tags that are more suited to such an application, rather than a smart tag which is an Sensor MCU first and RFID chip second).