Surface-wave phenomena in phased slot arrays with parasitic wire arrays

Blind spots observed in structures consisting of a slot array and parasitic straight wire arrays are investigated. Each blind spot is found to be associated with either a pattern null or the excitation of a surface wave on the corrugated structure consisting of the parasitic wires and conducting screen, with the slots shorted. The plane-wave-expansion technique is used to evaluate the coupling between arrays. It is shown analytically that for structures consisting of a single wire array, the blind spot can exist only at broadside, where there is a pattern null for the parasitic wires. For structures with two-wire arrays, such as an array of Clavin elements, a surface wave can be excited at a particular scan angle provided a certain uniformity condition in the structure is satisfied. The information presented is relevant to the incorporation of parasitic wire arrays for scan compensation