Compact laminated monopole antenna using air-gap for multi-band mobile terminals

This paper proposes a compact multi-band antenna using an air-gap between two laminated layers for hand-held devices. The air gap is adopted to increase the bandwidth of the antenna in the high frequency region and is useful to reduce its form factor. Based on the proposed techniques, a quad-band monopole antenna, including the GSM900, DCS1800, PCS1900, and WCDMA bands, was implemented on a low-cost ABS substrate. The implemented antenna has a form factor as small as 1.54 cc (30 x 9 x 5.7 mm3). It is on a separated FR-4 ground, whose size is 40 x 70 mm2, by 1mm. For each band, the average gains are -3.8, -2.87, -2.77, and -2.34 dBi and the corresponding average radiation efficiencies are 42, 52, 53, and 59%, respectively.