Читать книгу Introduction To Modern Planar Transmission Lines - Anand K. Verma - Страница 29

Heaviside reformulated Maxwell equation in 1884. He rejected the idea of EM‐wave propagation in a hollow metallic cylinder. In his opinion, two conductors, alternatively one conductor and the earth as a ground conductor are essential for the EM‐wave propagation. However, in 1893 J.J. Thomson expressed the possibility of the EM‐wave propagation in a hollow cylinder [B.12]. Next year, Oliver Lodge verified it experimentally. In the year 1895, J.C. Bose used the waveguide and horn antenna for the mm‐wave transmission and reception. In 1897 he reported the work at Royal Institution in London [B.5]. However, it was Rayleigh who carried out a detailed solution of boundary‐value problems. He obtained the normal mode solution, showing wave propagation in the form of the distinct discrete modes, i.e. the normal modes. He obtained his solutions for both the TE and TM modes, and introduced the concept of the cutoff frequency for modes. He further examined the EM‐wave propagation on a dielectric waveguide [J.30]. In 1920 Rayleigh, Sommerfeld and Debye continued the researches in this direction.

However, only in 1930 proper experimental investigations of the wave propagation in the waveguides were undertaken by G. C. Southworth at Bell Labs, and W.L. Barrow at MIT. In 1934, microwave commercial link was established, and in 1936, Southworth and Barrow discovered the possibility of using the waveguide as a transmission medium. However, they published their works only in 1936 [J.31, J.32, B.5]. During the same time‐period, Brillouin also investigated the wave propagation in a tube [J.33]. Serious analytical work on waveguides was further undertaken by J.R Carson, S.P. Mead, and S.A. Schelkunoff around 1933 [J.34]. Almost forgotten analytical works of Rayleigh was reinvented. Chu and Barrow further investigated the EM‐waves propagation in the elliptical and rectangular hollow metallic pipes [J.35]. During 1934, Schelkunoff extended the concept of impedance to the EM‐wave propagation in the coaxial line, and obtained the transmission line equations using the electromagnetic theory [J.36]. In 1937, he further extended the theory to the TE and TM mode guided wave propagations, and obtained the circuit models of mode supporting waveguides. Finally, Schelkunoff generalized the standard telegrapher's equation, using Maxwell's EM‐theory to represent an infinite set of uncoupled and coupled modes of a waveguide by the system of uncoupled and coupled transmission line equations [J.37–J.39]. Subsequently, his method has been extended to planar lines in an inhomogeneous medium supporting the hybrid modes [B.13].

During the World War‐II period, important theoretical and practical works were done in the field of waveguide technology for the development of the waveguide‐based components and systems. The development of Radar provided the impetus for such research activities.