Basis functions in the analysis of electrically long slots in rectangular waveguide with the induced magnetomotive forces method

When only one approximation function is used for every slot in a multielement system, Galyorkin's method is called the induced magnetomotive forces method (IMMFM). The solution in this case is more correctly an approximating function describing the distribution of magnetic current in the slot. We suggest here better functions for the IMMFM, which provide a good current approximation for longer slots. These functions are obtained by solving the integral equation for the magnetic current in a slot with the asymptotic method of averaging. The results of an investigation of the electrodynamic characteristics of such electrically long slots using these functions are presented. The slots are supposed to be cut in a broad wall of a rectangular waveguide.