Investigations on a triple mode waveguide horn capable of providing scanned radiation patterns

Feedhorn reflector antenna assemblies have been widely used for both satellite communications and Radar applications [1]. A dual mode feedhorn is presented in [2-3] where TEn and TMοi modes are excited to generate multiple phase centers when employed as a feed source for a reflector antenna. These papers [2-3] presented a technique of beam scanning in the φ = 90° cut plane only, thereby generation of multiple phase centers in the φ = 90° cut plane by control of the amplitude and phase of the modes. In [4] authors presented a tri-mode feedhorn design that employed TEn, TMn, and TE2ι modes, but the effort was to reduce the cross-polarization in the far-field pattern of a linearly polarized offset parabolic reflector antenna. In this paper, we present investigation results of a triple mode (TEπ, TMπ, and TE21) circular waveguide horn antenna with corrugated chokes which is capable of providing radiation pattern beam scanning in the range of θ = ±24° in both φ = 0° and 90° cut planes similar to the case of a conventional phased array antenna. This is achieved by exciting all the three modes simultaneously in proper amplitude and phase. Though not discussed here, it is capable of providing multiple phase centers in both the φ = 0° and 90° cut planes. The simulation design of the horn was performed using finite element method (FEM) based full wave analysis software Ansoft HFSS. The geometry and design of the horn is discussed in section II. Simulation results of the horn are discussed in section III. Finally, section IV presents conclusion and future study.