Compact Tri-Band Planar Monopole Antenna with ACS-Fed Structure

In this paper, a compact asymmetric coplanar strip (ACS)-fed printed monopole antenna for tri-band WLAN/WiMAX applications is presented. The proposed antenna is composed of a simple monopole with the high resonant mode at 5.8 GHz, an open-ended slot embedded on the ground plane with the low resonant mode at 2.4 GHz, and a meander trip shorted to the ground with the middle resonant mode at 3.5 GHz. The three resonance frequencies of the antenna can be controlled by adjusting the geometries and the sizes of the monopole, the slot and the strip. The antenna occupies a very compact size of 22 x 12 mm(2) including the ground plane, has nearly omnidirectional radiation characteristics and reasonable gain in the operating bands. The simple feeding structure, compactness and uniplanar design make it easy to be integrated within the portable device for wireless communication.