Design of Ka-band, broadband, omnidirectional, with a top metal disk antenna

In this report, a Ka-band, broadband, omnidirectional, with a top metal disk antenna is proposed. The antenna is fed by an air waveguide. The TE10 mode of the waveguide can efficiently be converted into an air coaxial TEM mode by a compact waveguide air coaxial transition. After matching and adjusting, the dielectric substrate is loaded and then transited to the metal radiation structure loaded with a top metal disc to obtain omnidirectional electromagnetic waves efficiently converted to free space. By optimizing the sizes of waveguide to air-coaxial transition structure and disk, and so on, a good broadband omnidirectional antenna performance is finally achieved. The measured fractional impedance bandwidth is larger than 30% with the reference of S11 & LE;-10 $\leqslant -10$ dB, which fully verifies the rationality of the design. In addition, measured patterns at the plane of different azimuth angles almost coincide with each other, which shows an excellent omnidirectional pattern.