A novel loop antenna design integrated with metal ring for mobile device application

A novel loop antenna design which is integrated with the exterior metal ring of a mobile device for GSM900/1800 operation is proposed. The proposed loop antenna consists of an impedance transformer which is printed on a 1.0 mm FR4 substrate and the exterior metal ring of a mobile device. The loop antenna is fed from the end of the impedance transformer, and then was connected with the exterior metal ring to excite a half-wavelength loop resonant mode. Through the adjustment of the length and width of impedance transformer, the good impedance bandwidth was obtained. Due to its integrated structure with exterior metal ring and simple design concept, the proposed antenna is very suitable for the GSM900/1800 antenna application of a mobile device, especially in a mobile smart phone. Besides, the good antenna efficiency and radiation performance were obtained. Details of the proposed antenna and experimental results are presented and discussed.