Radiation Of An Electromagnetic Pulse From The Open End Of A Circular Waveguide

When an electromagnetic pulse (EMP) traveling along the inside of a waveguide reaches the open end, it will cause radiation. Can this EMP radiation be an electromagnetic missile,' i.e., a pulse with slowly decaying energy? This analysis of radiation from an open circular waveguide attempts to provide the answer. The problems of radiation of acoustic and electromagnetic waves from a cylindrical waveguide have been solved for many years.2-4 However, interest then was confined to the CW case in the low-frequency region, i.e., when the wavelength A is of the same order of magnitude as the radius a of the tube. It is interesting and significant to study the radiation of an EM pulse in which the wide high-frequency band (λa) plays an important role. The problem of radiation of an EMP is solved and examined first in the frequency domain. The analysis proceeds according to the following steps: 1) Specifying the incident currents for the TEn, modes; 2) Establishing the coupled integral equations for the currents; 3) Using the Wiener-Hopf technique to solve the equations for the currents; 4) Deriving the formula for the electric field along the axis; 5) Evaluating the asymptotic behavior of the radiated field; and 6) Transforming the radiated field into the time domain and calculating the Poynting vector.