An Omnidirectional and Low-VSWR Ultra Wideband Antenna for a Frequency Band of 6 to 40 GHz
We have proposed an omnidirectional-in-azimuth, low voltage-standingwave-ratio (VSWR), and easy-to-construct antenna for ultra-wideband (UWB) systems. Omnidirectional and low-VSWR requirements are essential for applications such as UWB channel sounding. The proposed antenna consists of a circular ground plane and a teardrop that is defined as a combination of a finite cone and a sphere inscribed inside the cone at the cone’s base. This antenna can be considered either as a rounded finite monocone antenna or as a simplified volcano smoke antenna. Assuming 50-Ω excitation, the optimum half-cone angle is 48°which gives the lowest maximum VSWR. Following a prototype in the frequency band of 3 to 20 GHz, we constructed the 6 -40 GHz version. The teardrop was 12.5 mm high (the quarter wavelength at 6 GHz) and ground plane was 50 mm in diameter (significantly larger than any quarter wavelength in the designated bandwidth for 6 -40 GHz). The teardrop is connected to the inner conductor of the coaxial cable that penetrates the ground plane. The tip of the inner conductor of a K connector was inserted into the apex of the teardrop.
KeywordsGround Plane Group Delay Vector Network Analyzer Quarter Wavelength Absolute Gain
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