The imperfectly conducting coaxial line

In order to determine the range of validity of certain elementary concepts in waveguide theory, the propagation of electromagnetic waves along and through a coaxial line with imperfectly conducting walls is studied in some detail for a particular method of driving. In particular, it is found that the usual concept of attenuation is meaningful only for a certain range of distances from the driving point. Beyond this distance, the electromagnetic field in the coaxial line behaves more like a radiation field. The explanation is supported by the behavior of the electromagnetic field in the imperfect outer conductor of the coaxial line. It is also found that the solution in terms of the “mode” concept has a surprisingly limited region of validity. The reflection coefficient, the radiation pattern and the transverse distribution are also determined.