For achieving low cross-polarization component in addition to circular-coverage pattern in compact structure, this paper proposes a novel multimode horn with arbitrary coaxial-corrugation configuration which plays two roles of mode converters and chokes. The proposed horn can be designed by iteration of non-linear optimization procedure based on generalized scattering matrices pre-calculated by the mode-matching technique. We show a compact horn with four coaxial corrugations for shaping circular-coverage beam over frequency range of bandwidth 20%. The effectiveness of the designed horn is discussed by evaluating VSWR and radiation characteristics in X-band numerically and experimentally.

In this paper the characteristics of millimeter-wave antenna composed of layered magnetic and dielectric slabs with different corrugation are described for the transverse electric mode. A corrugation of the upper magnetic layer contacts with air, and the lower surface of the dielectric slab having corrugation in matalized. The extinction coefficient clarifying the characteristics of the leakage wave is systematically derived by using the perturbation method combined with the multiple space scales. As an example the radiation efficiency becomes a value of about 89% by using the typical physical parameters in the frequency range from 52 to 54 GHz.

The dielectric rod waveguides with corrugation consisting of nonintegral-ratio period waves are investigated numerically. The leakage characteristics of HE11-type wave in the waveguide is analyzed by applying Yasuura's method. The complex propagation constants and the far field patterns are presented. The radiation pattern of a fabricated waveguide with corrugation agrees well with the calculated value. The dependence of radiation characteristics on the corrugation form is discussed. It is shown that the leakage directions and the intensity of leaky waves are controlled independently one another. The radiation pattern can be synthesized by choosing the geometric parameters of the corrugation properly.