A Compact Vertically Polarized Fully Metallic Quasi-Yagi Antenna With High Endfire Gain

A compact fully metallic antenna with high endfire gain and vertical polarization is presented for applications that require the antenna to be mounted on large metallic platforms. The proposed structure includes one driven element on a ground plane, in addition to several parasitic directors and reflectors. The antenna behaves like a Yagi array, but with vertical polarization, where multiple directors and reflectors are used to enhance the endfire gain in the plane that contains the ground surface. The driven element is an upside-down U-shaped metallic strip with short vertical sides connected to the ground plane. The radiation is predominantly emitted from these vertical sides giving the antenna its vertical polarization radiation. Directors and reflectors are designed based on the driven element, with directors having the center of the U-shaped strip connected to the ground plane and reflectors without shorting pins in the middle. A prototype is fabricated with a volume of 104 times 55times 6 mm3. The measured bandwidth is 18% (5.32-6.38 GHz). The variation of endfire gain is 2 dB around the nominal gain of 10.3 dBi across the bandwidth.