Simple Folded Monopole Slot Antenna for Penta-Band Clamshell Mobile Phone Application

An internal clamshell mobile phone antenna using a simple dual-band folded monopole slot for covering penta bands of WWAN operation is presented. The folded monopole slot has a length of about 60 mm only and is easily printed on the top portion (10 times 40 mm²) of the main circuit board and suitable to be placed at the hinge of the clamshell mobile phone. By further placing the connecting strip between the two ground planes to be in the vicinity of the open end of the monopole slot, the two (main and upper) ground planes of the clamshell mobile phone can also be excited to be efficient radiators (dipole-like chassis or groundplane modes excited through the strong electric field occurred at the slot´s open end). By incorporating the resonant modes contributed from both the monopole slot and the two ground planes, two wide bands at about 900 and 1900 MHz are formed, which easily cover GSM850/900/1800/1900/UMTS operation. Owing to the additional resonant modes contributed by the two ground planes, the use of a simple folded monopole slot is sufficient to cover penta-band WWAN operation. This leads to compact size for the proposed clamshell mobile phone antenna. Details of the proposed antenna, including its SAR results, are presented.