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 prveious 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.