Multiband Dual Spiral Stripline-Loaded Monopole Antenna
We propose a multiband antenna that exhibits a dual coupling characteristic and dual frequency operation using a dual spiral stripline-loaded monopole in conjunction with L-shaped slots in a ground plane. The slots allow the upper part of the ground plane to function as an additional monopole that resonates in concordance with the existing resonances of the upper and lower spiral stripline monopoles. As a result, the impedance band- widths are greatly enhanced while maintaining relatively good omnidirectional radiation characteristics. The proposed antenna occupies a volume of 36 times 7 times 102 mm3 including the ground plane, and the measured impedance bandwidths with VSWR < 2 simultaneously cover CDMA, GSM900, DCS1800, PCS1900, UMTS, IMT-2000, and WiMAX2350 bands. We describe the detailed antenna structure and present measurement results.