Phase center of an H-plane sectoral horn between parallel conductor plates

In feeding parallel plate slot arrays with plane waves propagating between parallel conductor plates, a dielectric plate lens or a parabolic cylindric al reflector is often used to generate the plane waves. Such a lens or a re flector requires a point source at its focus, since these lenses are design ed by using a geometrical optics approach and actually are fed by H-plane s ectoral hems. However, it is impossible to regard the horn as a point sourc e, because its aperture is generally several wavelengths. Thus it is essent ial to determine the phase center of the sectoral horn in order to put the feeding system to practical use. Moreover, the lens and reflector are usual ly placed in the Fresnel region of the horn and are designed to operate at the widest feeding angle possible. In this paper a method to determine the phase center of the horn that is applicable in the wide angle Fresnel regio n is proposed, and several charts for its location are presented. This meth od is ascertained to be fully practical by means of several numerical and e xperimental investigations. A trial-fabricated plate dielectric lens and an offset parabolic cylindrical reflector were tested and found to operate ap proximately in accordance with the principles of geometrical optics, if the ir focii are arranged on the phase centers given in this paper. (C) 1998 Sc ripta Technica.