Variational expression for propagation coefficient of an electromagnetic wave propagating along a closed rectangular chirowaveguide

A variational expression involving the transverse components of the electric field and their transverse derivatives is established for the propagation coefficient of an electromagnetic wave propagating along a lossless rectangular chirowaveguide with perfectly conducting walls. The solution providing the propagation coefficient of the dominant mode is given in terms of a very simple analytical expression enabling a tractable analysis of the device. The propagation coefficient of a second propagating mode is obtained simultaneously. The agreement between these variational results and those obtained by other methods is found to be very good