The long Yagi-Uda array

Abstract

The King-Sandler array theory is used to analyze the excitation of a surface wave along a semi-infinite Yagi array, as well as the scattering of such a wave at the end of a semi-infinite array. A method for approximately analyzing the behavior of finite Yagi arrays is presented which involves the matching of two terminal-zone solutions for semi-infinite arrays. Before attempting to correlate the derived theory with the more rigorous array theory, an experimental study of a twenty-element Yagi array was undertaken, and all results are shown to be accurately predicted by the King-Sandler theory. An extensive set of numerical data is presented to compare wave theory with array theory, and once again the agreement is excellent. Finally, the new theory is shown to predict a certain critical point in the data at which the wave solution ceases to exist. This point is also observed to enter dramatically into the King-Sandler solution, thus providing a final contribution to the evidence which links the wave theory to the accepted King-Sandler theory.