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A broadband coplanar stripline-fed Yagi-Uda antenna is presented. The antenna has a feedline structure that is much simpler than other Yagi-Uda antennas, and provides more design flexibility in arranging the reflector owing to the absence of a large ground plane. To improve the impedance match, a taper is inserted between the wide-line/small-gap and the narrow-line/large-gap CPS. The proposed antenna has a bandwidth of 3.9-5.9 GHz for a - 10 dB reflection coefficient and a gain of 6.5-8.0 dBi. At the centre frequency of 4.9 GHz, the antenna has gain of 7.1 dBi, and a half-power beamwidth (HPBW) of 73° in the E-plane and 98° in the H-plane.
Introduction: In recent years, planar Yagi-Uda antennas have attracted much interest owing to their broad bandwidth, high gain, ease of fabri- cation and low cost [1], These Yagi-Uda antennas can have several different feeding structures, such as a microstrip line feed with a micro- strip-coplanar stripline (MS-CPS) transition [1, 2], coplanar waveguide (CPW) feed with a coplanar waveguide-coplanar stripline (CPW-CPS) transition [3], and a microstrip line feed without any transition structure [4]. They can be easily integrated with wireless communication systems because they are both small and broadband. However, the reflectors of the antennas cannot be well optimised since they utilise the ground plane as a reflector, and hence the radiation pattem is not as good as that of a conventional Yagi-Uda antenna.
A broadband CPS-fed Yagi-Uda antenna is described in this Letter. The proposed antenna has a simpler feedline structure than existing planar Yagi-Uda antennas. The antenna does...