Design of A Quad-Band Waveguide Filter with Compact Size and Large Frequency Ratio

In this paper, a quad-band waveguide filter with 200 MHz bandwidth for each passband is introduced. The maximum frequency ratio could reach 1.5 for the center frequency by adjusting the length width ratio of reasonable cavities. The distinctive feature of the filter is that thin rectangular cavities are stacked parallel to the input/output ports, forming a multi-layer structure. As there is no inter-layer coupling, each layer does not affect each other, and each layer can independently control the filtering response of a passband. Additionally, one transmission zero (TZ) is generated between any two adjacent passbands, which is conducive to enhancing the attenuation between pass bands. The Simulated result reasonably supports the validity of the proposed filter.