Design of a circularly-polarized two-element microstrip antenna array excited by a cross slot on a broad wall of the rectangular waveguide for a waveguide-fed planar array

This paper presents design of a circularly-polarized (CP) two-element microstrip antenna (MSA) array excited by a cross slot on a broad wall of the rectangular waveguide for a waveguide-fed planar array. In order to realize a CP slot array arranged at a spacing of one guided wavelength on a broad wall of the waveguide, it is proposed to place two CP MSA elements on each cross slot with a dielectric substrate. In this paper, a series-fed two-element CP MSA array excited by a cross slot on a broad wall of the rectangular waveguide is designed as an element of a waveguide-fed CP planar array on the broad wall by using ANSYS HFSS. The design frequency is 11.2 GHz and an X-band standard waveguide is used. It is confirmed by the simulation that CP radiation with an axial ratio of 2.2 dB as well as a sharp main beam in the waveguide axis plane for grating lobe suppression can be obtained by the designed MSA array at the design frequency.