Waveguide bandstop filter based on dual-mode $\Pi$-shaped cavity

The paper considers a waveguide reject dual-mode $\Pi$-shaped cavity operating on TE$_{101}$ modes. It is shown that this reject cavity exhibits a pseudo-elliptical amplitude-frequency response. A four-order bandstop filter based on cavities of this type is described. The influence of the geometric dimensions of the waveguide reject $\Pi$-shaped cavity on its frequency response is considered.