Triple-wideband inverted-F frame antenna for the LTE metal-casing smartphone

A frame antenna based on the inverted-F antenna (IFA) structure for the LTE (long term evolution) metal-casing smartphone is presented. The antenna uses a frame section along the short edge of the metal casing as the IFA's radiating strip. There are no gaps required at the two side edges of the smartphone. The frame section is connected to a feed circuit board (FCB) to achieve wider bandwidth. With a narrow metal clearance of 2 mm in the metal back cover, the antenna can provide a triple-wideband LTE operation to cover 824~960 MHz, 1710~2690 MHz, and 3400~3800 MHz bands. Moreover, by selecting different inductances of the inductor at the shorting strip of the IFA, the low band of 704~960 MHz can be covered. Details of the proposed antenna structure and its working principle are described, and experimental results of the fabricated antenna are presented.