Study And Design Of Stacked Dual-mode Circular Waveguide Bandpass Filter

With the rapid development of the fifth generation(5G)mobile communication systems,the demand for radio frequency and microwave eqipments becomes more and more strict.In these devices,high-performance bandpass filters have been the focus of many scholars and experts.In this context,a stacked cavity bandpass filter is designed and fabricated.A stacked dual-mode circular waveguide bandpass filter is studied in this paper.the dual-mode single cavity circular waveguide filter is realized based on the single circular cavity with coupling window between input/output waveguide ports and the circular cavity.And the intersection point of the center lines of the two rectangular waveguides coincides with the center of the circular cavity.At last,two dual-mode single cavity circular waveguide filters are cascaded by stacking technique.The bandwidth of the stacked dual-mode circular waveguide filter filter is from 3.3 GHz to 3.7 GHz,which expand the 3dB fractional bandwidth to 13.7%.Each cavity has two resonant modes,which can generate and control two transmission zeroes at specific frequencies.The filter has the following features:1.Without any complex tuning screws or coupled screws,the filter poles and the transmission zeros are controlled by the size of the resonator and the coupling window.2.The whole filter is completely sealed by metal at the same height,and the fabrication cost is low.3.Utilizing the dual mode characteristics of the circular waveguide and stacking technology,the size of the filter is greatly reduced.Finally,the industrial milling technology is used to fabricate the stacked dual-mode circular waveguide bandpass filter.The measured insertion losses are around 0.5 dB in the passband(from 3.4 GHz to 3.6 GHz),and the measured results are in good agreement with the simulation results.