L. Gaffour, WKB METHOD FOR ANALYZING THE ELECTROMAGNETIC-FIELD IN A CIRCULAR WAVE-GUIDE WITH LINEARLY MOVING BOUNDARY, Journal of electromagnetic waves and applications, 10(6), 1996, pp. 757-764
The analytical study of the electromagnetic field in a circular wavegu
ide with linearly moving boundary has been made in [1]. In this paper,
we analyse the case where the argument of the LEGENDRE's associate fu
nctions is superior to 1. The W.K.B. method is used for solving this p
roblem. The expressions of field have been determined. It is shown tha
t the field has a modal nature and the modes are dynamics, each having
an instantaneous frequency. Also a criterium of precision is given.