Circular NFC R35 Antennas Mikroe Circular NFC R35 Antennas are designed for use as an extension of development boards. They can be placed remotely on a desired place like plastic casings, existing products, or even under displays. The antennas are designed in a circular shape with a diameter of 35mm. This antenna is used for NFC and RFID applications that work on a 13.56MHz frequency. This antenna can be connected to an existing NFC Extend Click board or any device with the male U.FL connector.