Planar monopole folded into a compact structure for very-low-profile multiband mobile-phone antenna

摘要

A planar monopole consisting of three branch strips and folded into a rectangular-box-like compact structure for very-low-profile GSM/DCS/PCS multiband mobile-phone antennas is presented. The three branch strips are designed to operate as quarter-wavelength structures at 900, 1800, and 1900 MHz, respectively, and the obtained impedance bandwidths cover the required bandwidths of the GSM band (890-960 MHz), the DCS band (1710-1880 MHZ), and the PCS band (1850-1990 MHz). The proposed antenna has a compact size of 6.5 mm in height, 6 mm in width, and 25 mm in length, and can be mounted on top of a mobile phone with a small distance of 3 mm to the ground plane, resulting in a very low profile of 9.5 mm (less than 3% of the wavelength at 900 MHz) from ground for the proposed antenna in practical applications.