Compact Vertically Polarized Omnidirectional Ultra-Wideband Antenna and Its Band-Notched Filtering Application

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 traditionalUWBantennas 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 (0.19 lambda(L) x 0.19 lambda(L) x 0.06 lambda(L), where lambda(L) 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.