Currents on generalized Yagi structures

Characteristics of currents produced on an infinite linear array of parasitic radiators when one of the radiators is excited are found. Yagi antennas use arrays of electric dipoles; detailed analyses and results are given for a generalized Yagi structure in which the dipoles are inclined at an arbitrary, angle to the array axis. These results suggest a simple mechanical means for broadbanding. Calculations are carried out within a network formulation. The integral solution obtained from this formulation is used to demonstrate the interrelation between the properties of the array of radiators excited parasitically or excited as a phased array. The solution simplifies remarkably when the angle of inclination of the dipoles is54.74. The surface-wave components and the (feed) correction currents are then explicitly evaluated. Although for conventional Yagi structures surface-wave solutions have been found only for capacitive dipoles, for sufficiently small angles of inclination surface waves can exist on arrays of inductive dipoles.