Sinusoidal profiled (Bowl) corrugated conical horn
Image of the Sinusoidal profiled (Bowl) corrugated conical horn.

The sinusoidal profiled corrugated conical horn antenna consists of a number of sections, namely, circular waveguide, mode converter, phasing section and a profiled Sinusoidal flare. The shape of the sinusoidal profiled flare is controlled by a profile power index. According to [Granet], the power index should be smaller than one for low sidelobes. The optimised power index value was determined to be 0.8 giving the flare its characteristic ‘bowl’ shape.

This antenna may be designed for two different radiation performance criteria, namely, low sidelobes or a symmetrical radiation pattern. Depending on the selected performance, the slot-to-ridge width ratio is designed to be roughly 3:1 (for symmetrical beamwidth design) and 4:1 (for low sidelobe level design), whilst the pitch (slot width + ridge width) remains constant. The pitch is roughly equal to a tenth of a wavelength at the centre frequency [James].

Below is a comparison between designs for the two performance criteria and the linear corrugated conical horn already present in Antenna Magus. The structures compared are designed for 20 dBi gain and it is clear that the profiled horns are shorter than the linear horn. The profiled horns are roughly 17% shorter.

Size comparison of 20 dBi design – low sidelobes (left), symmetrical beam (middle) and linear profile (right)
E-plane radiation pattern comparison of the 3 structures
H-plane radiation pattern comparison of the 3 structures