Rectangular NFC Antennas Mikroe Rectangular NFC Antennas are designed for use as an extension of development boards and placed remotely in a desired place. This includes plastic casings, existing products, or even under displays. The antenna is designed in a circular shape with a diameter of 40mm. 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.