On the performance of metallic-wall conical horns with centrally-loaded dielectric material

A known asymptotic-analysis technique is extended to determine the HE₁₁ mode electromagnetic fields which can exist inside and across the aperture of a metallic-wall conical horn which is centrally-loaded with a concentric dielectric material. Two horns of special interest are then examined: the foam-core air-lining (FCAL) horn and the dielectric road-loaded (DRL) horn because their radiation patterns (especially those of the FCAL) are close to those from an ideal corrugated horn (CH) of the same size, which the subject asymptotic-analysis technique can also treat. Copolar and 45 degrees plane crosspolar pattern computations and gain, along with corresponding measurements, are given for several horns of the above types and show very good agreement. However, the limitations of this asymptotic technique, using only the single HE₁₁ mode, in predicting extremely good 45 degrees plane crosspolar patterns are described.