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A coplanar waveguide (CPW)-fed, multi-band, trapezoidal monopole antenna with linear and circular polarization realized in a single substrate layer is presented. It is demonstrated that, polarization of the antenna originate from resultant surface currents controlled by the physical aspects of the trapezoid. A prototype fabricated on Rogers RO4350B® substrate with dielectric constant 3.48 occupies an overall dimension of 55 × 50 × 0.762 mm3. The antenna provides a 2:1 VSWR bandwidth of 80% (from 1.55 GHz to 3.60 GHz) and 8% (from 5.13 GHz to 5.55 GHz) in the first and second band respectively. It also exhibits a 3 dB axial ratio bandwidth of 8% (from 2.21 GHz to 2.40 GHz) in the IEEE 802.16e WiMAX band. In addition, the antenna facilitates quasi omnidirectional coverage along with moderate gain and efficiency. A parametric study of the key parameters is also performed and the mechanism of polarization is described through surface current analysis.
Date of Publication: May 2012