Coupled surface waves and broadside arrays of end-fire antennas

The concept of coupled surface waves is introduced to describe the action of element interaction in a broadside array of traveling-wave end-fire antennas. These coupled waves are formulated in terms of an interaction matrix, whose elements either can be determined experimentally, or, for some antenna structures, can be computed. Two methods of pattern evaluation based on two well-known approaches to end-fire antennas are then presented. The roles of interaction in the two methods turn out to be quite different, and the method which assumes radiation at the end of the antenna appears to be more favorable. A criterion on the over-all interaction effect on array pattern is introduced which indicates under what condition coupling can be neglected. Finally, the nature of patterns obtainable with different element spacings is examined.