Quadruple-Mode Wideband Bandpass Filter Using Symmetric Structure in Single Cylindrical Cavity

This work proposes a four-pole wideband bandpass filter using a single metallic cylindrical cavity. The filter employs quadruple-mode resonator by using simple symmetric pair of perturbation and 2 symmetric feeding lines are deployed to implement a quadruple mode resonator. Both, the pairs of perturbation and extended feeding line, work together with the mode to constitute a four-pole wide passband with a fractional bandwidth of 46% at the central frequency of 3.9 GHz. To prove the validity, the simple symmetric proposed bandpass filter is fabricated from Aluminum 7075 using CNC machining technology. Measured S-parameter frequency response have satisfactorily matched with the simulated results.