A Quasi-Planar Wide Band Conical Antenna
The conical antenna has wide input impedance bandwidth and omni-directional radiation pattern (Kawakami and Sato, 1987; Liang and Wah, 2000). This special property makes it irreplaceable in some modern applications, for instance, in portable or mobile communications requiring very wide-bandwidth channels or where continuous frequency coverage is needed. The prototype of the conical antenna has a threedimensional structure. It is mechanically difficult to fabricate and integrate. In (Gentili et al., 2004), a dielectric loaded conical antenna is reported, where the dielectric loading mechanically stabilizes the conical antenna while maintaining wide band input impedance characteristics. However in (Gentili et al., 2004), the loading material is magnetic, hence not practical; and the antenna still has a three-dimensional configuration. In this study, a conical antenna with metallic cones coated on non-magnetic dielectric slab is proposed. The proposed antenna has a quasi-planar structure. It is mechanically stable, and easy to build and integrate with planar circuits. A full wave analysis code is developed to simulate this novel conical antenna. It is shown that the input impedance remains close to a constant value when the loading material’s dielectric constant is chosen within a wide range. A quasi-planar conical antenna is fabricated with high density polyurethane foam as the loading material. The measurement data verifies the simulation results. Techniques to reduce the antenna size and adjust the radiation pattern are also discussed.
KeywordsInput Impedance Ground Plane Voltage Standing Wave Ratio Planar Circuit Antenna Geometry
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