Highly Omnidirectional Monopole-like Radiation With SIW Slot Antenna in Ka-Band

A monopole-like radiation pattern with high omnidirectivity in Ka-band is generated by substrate integrated waveguide (SIW) slot antenna. Two pairs of symmetric slots are designed to facilitate the radiation of two out-of-phase elements based on the fundamental TM
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mode in SIW cavity, leading to the cancellation of electromagnetic (EM) fields in the broadside direction, thus yielding a monopole-like radiation pattern. Moreover, four metal vias are properly positioned to improve the impedance matching. Simulation results show a highly omnidirectional radiation pattern in azimuth plane (θ = 54°) and a deep null (<-95 dB) in broadside, and the realized gain is 1.81 dBi at 28.86 GHz.