Studying of a waveguide insert with a rectangular window in the millimeter wavelength range

A number of examinations of the influence of the rectangular window geometrical sizes on the resonant properties of the insert was made. The expressions for the transmission and reflection coefficients were calculated. The graphs of the resonant frequency dependences versus the insert length and width of the rectangular window were shown. The frequency dependence of the reflection coefficient with various heights of the window was presented; also fractional-rational approximation was carried out for this function, as a result of which the values of the poles (natural frequencies) and zeros were obtained.