Design of Six-Cavity Dielectric Waveguide Filter with Flat Group Delay

A six-cavity dielectric waveguide filter (DWF) with flat group delay characteristics in the passband is designed in this paper. Control of the coupling slot distance is achieved by opening a single-sided magnetic coupling slot. The effect of the transmission zero position on the group delay is discussed. Complex transmission zeros are introduced in the CQ structure to equalize the group delay in operation band. By analyzing the effect of the spacing of the coupling slots in the CQ on the group delay responses, the appropriate coupling coefficient is achieved. Through simulation and physical testing, a filter that meets the design specifications is obtained.