Compact vertically polarized omnidirectional ultra-wideband antenna and its band-notched filtering application

Abstract

This paper first proposes a 3D printed, compact, low-profile, ultra-wideband (UWB) antenna with vertically polarized omnidirectional radiation characteristics. The antenna is composed of one triangular feeding structure, one triangular shorted structure, a common capacitive top hat, and two parasitic metallic pins. Compared with traditional UWB antennas with symmetrical configuration, the proposed UWB antenna is a three-dimensional version of inverted ‘‘F’’ with asymmetrical structure. The proposed antenna can realize compact aperture and low profile (0.19λL × 0.19λL × 0.06λL, where λL is the free-space wavelength of the lowest operating frequency). Two parasitic pins are utilized to enhance the omnidirectionality of the antenna in the azimuth plane. The impedance bandwidth is greater than 10:1 (2.96–30 GHz) for VSWR < 3, and the bandwidth with horizontal radiation pattern ripple better than ±5 dB is more than 4.9:1 (2.96–14.5 GHz). Second, this UWB design is modified to realize dual bands with a deep band-notch by adding a split gap inside the antenna. The proposed band-notched antenna is designed with the bandwidth of 2.4–2.5 and 5–10 GHz for VSWR < 2 with good horizontal radiation pattern omnidirectionality, which can be used for 2.4/5 GHz WLAN applications. The prototypes of the proposed UWB and band-notched antennas are fabricated by metallic 3D printing, and the simulated and measured results meet well.