Forty years ago: Maxwell´s theory invades engineering - and grows with it

A story of my personal involvement in a rapid evolution of high-frequency electrical communication that began forty years ago and led to the merger of Kelvin´s transmission-line theory, which had been the cornerstone of the telephone engineer´s thinking, and more inclusive Maxwell´s field theory is described. The early sections of this paper describe the state of electrical theories in those days, the environment in which I found myself, my previous interests and education, and the problems I was presented with; these are the four factors which determined the direction of my subsequent work. In the course of this work I found that, contrary to the then prevailing belief, Kelvin´s transmission-line equations were consistent with Maxwell´s field theory and the restrictive assumptions usually made in derivations of these equations are sufficient but not necessary. The major part of this paper presents a sketch of the gradual development of comprehensive wave-propagation equations which are applicable to a wide variety of guiding structures. These equations form also the basis of a comprehensive antenna theory. The concluding section describes briefly my mathematical theory of linear arrays which led to the discovery of superdirective arrays.