Compact Multimode Monopole Antenna for Metal-Rimmed Mobile Phones

A compact multimode monopole antenna for heptaband metal-rimmed smartphones is proposed. The metal bezel is kept unbroken and no lumped element is needed. To cover the low band, the bezel mode is excited by a capacitive coupling vertical plate, and a bandwidth enhancement technique is introduced for this mode. For the high band, printed multiple branches on both sides of substrate are well designed to obtain multiple modes to cover a wide band. With the proposed structure, the frequency bands can be widened by tuning and optimization. The new-type monopole occupies an area of 60×5×5 mm3 on a 120×60 mm2 system board, which has a narrow ground clearance and a low profile. A prototype is fabricated and measured to validate the proposed design. Measured results show that the proposed antenna has two impedance bands with S11 less than -6 dB, i.e., 23% for the low band (0.76-0.96 GHz) and 57% for the high band (1.51-2.72 GHz). The proposed monopole antenna is capable of covering the GSM/DCS/PCS/UMTS and LTE2300/2500 bands for modern metal-rimmed mobile phone applications.