A new method for obtaining maximum gain from yagi antennas

In conventional Yagi design, optimum performance requires separate adjustments in a number of parameters-the array length and the height, diameter, and spacing of the directors and reflectors. By introducing the notion of a surface wave traveling along the array, it is possible to demonstrate experimentally the interrelationship between these parameters. With this, the gain then depends only on the phase velocity of the surface wave (which is a function of the height, diameter, and spacing of the directors) and on the choice of the reflector. Thus, maximum gain for a given array length, for any director spacing less than
0.5 \lambda
, can be obtained by suitable variation of the parameters to yield the desired phase velocity. A design procedure that provides maximum gain for a given array length is presented.