Radiating Properties of Dielectric Covered Apertures

In designing phased a r r a y s for r a d a r and other types of communication systems, it is generally necessary to provide some degree of environmental protection. One configuration which suggests itself is the flush-mounted " r a d o m e " (Fig. 1), made of a suitable refractory ceramic such as beryllia, alumina, or boron nitride. However, since these materials typically have relative dielectric constants greater t h a n unity, such a covering sheath can be expected to influence the electrical performance of the antenna and hence of the system to which it belongs. T h e two antenna characteristics of greatest interest are: (i) the individual element input impedance and (u) the radiation pattern corresponding to a given aperture illumination. T h e effects of a covering sheath on the input characteristics of infinite rectangular waveguide a r r a y s have been discussed by Galindo and Wu, using a technique of spectral analysis. 1 Although the radiation p a t t e r n of a single element in an a r r a y environment can also be obtained as a by-product of this analysis, it is still useful to study 2169