"Lost beams" from a dielectric covered phased-array aperture

Mutual Coupling

“…The higher mode can be produced by external or internal structure. Examples of external structure causing a blind angle are a dielectric radome covering each element or row of elements (Lechtreck, 1968), a dielectric sheet placed on the array face (Bates, 1965;Byron and Frank, 1968;Wu and Galindo, 1968;Gregorwich et al, 1968), and a dielectric plug protruding from the mouth of each waveguide element (Hannan, 1967a). In all cases, the active wave impedance at the array face is modified by the external structure so as to produce a dominant and higher mode resonance at a particular scan angle; the higher mode exists primarily outside the face.…”

Very wide-band phased-array antenna

“…These surface-type wa.ves can give rise t:o a.rray blindness, which ca.n be observed in array simulators [6]- [8] and element pat,terns but are not predicted by t,his design procedure. Byron and Fra.nk [6] have reported a method whereby waveguide array simulat,ors may be used to approximately predict the slow-wa.ve phenomenon.…”