Broadbanding of feed horn utilizing corrugated waveguide with two kinds of slots

This paper presents an analysis of the dual corrugated waveguide, consisting of two kinds of slots with arbitrary shapes and a technique for broadbanding of a conical horn with a small flare angle made of this waveguide. First, the characteristic equation for the dual corrugated waveguide was derived under an assumption that the admittances of the two kinds of slots are known. By this arrangement, the propagation characteristics of the waveguide can be easily determined once the admittances of the slots are substituted into the equation when the shapes of the slots are modified. Next, the results were applied to the dual corrugated waveguide with two kinds of parallel slots. The effective frequency ranges, not previously clear, of the dual corrugated conical horn were found out when the width ratio of the two slots was modified. Hence, the design data for a conical horn were provided. Next, for broadbanding of the dual corrugated conical horn, a ring-loaded dual corrugated waveguide, made of shallow parallel slots and deep ring-loaded slots, was proposed. When this waveguide is applied to a horn, the bandwidth can be increased 1.3 times.