Design of rectangular horn arrays with oversized aperture elements

The possible existence of blind spots, due to forced aperture resonances, is demonstrated theoretically and experimentally at 14 GHz in rectangular grid arrays of tapered rectangular horn elements with oversized (overmoded) apertures. The dominant contributor to these blind spots is the resonance of the equivalent transverse magnetic ( ) waveguide mode. The numerical results based upon our approximate methods of formulation and solution of the array boundary value problem agree well with experiments. A method for eliminating the blind spots by proper taper design is presented and experimentally verified. The analytical methods used in this work could possibly be extended to conical horus and other tapered-structure arrays as well as other periodic grid geometries. New simple and accurate formulas for the zeros of Bessel and Legendre functions and their derivatives are obtained as a result of this analysis.