Analysis and synthesis of slotted strips notch and bandstop filters with the aperture method

Simplest notch and bandstop filters based on the multi-slot irises in a rectangular waveguide are analyzed with accounting the iris thickness using the Galerkin´s method and the Green´s functions technique. The problem is reduced to the system of several coupled integral equations, derived from the electromagnetic boundary conditions. The magnetic fields on the inward and outward surfaces of the slots are approximated with sinusoidal Fourier set of basis functions. Theoretical results are presented for scattering parameters of the slot system and these are compared with experiments and some earlier results obtained with the mode-matching method. It is shown, that the method used enables to avoid inverting large full matrices and to obtain successful convergence. Dependences of resonance frequency on the slot dielectric filling permittivity are investigated.