Multiband Waveguide Filters With Compact Size and Large Frequency Ratio

In this article, a class of multiband filters, including dual- and triple-band filters, are proposed using thin rectangular waveguide cavities, which are stacked and coupled to the input–output ports in parallel, leading to a multilayer configuration. Each layer could independently control the filtering response of each individual passband, including the operational frequency, insertion loss (IL), and bandwidth. Compared to the reported multiband filters, the proposed multiband filters could simultaneously achieve a large frequency ratio, compact size, independent control of each passband. Moreover, the proposed configuration could be easily extended to filters with more passbands by increasing the number of layers. The design procedures are detailed and one dual-band filter is fabricated. The measured results validate the proposed approach.