Dual-Band Bandpass Filter with Large Frequency Ratio and Independently Tunable Center Frequencies

Abstract

For the first time, a dual-band bandpass filter with independently tunable center frequencies was implemented to support microwave and millimeter-wave frequency bands simultaneously. To achieve the desired high-frequency ratio, the microstrip element is combined with the metallic cavity element through the aperture coupling mechanism. Meanwhile, the proposed approach allows the independent control of the two operating frequencies. For demonstration, a tunable dual-band bandpass filter was designed, fabricated and measured. A maximum tunable frequency ratio up to 24 can be achieved together with the independent center frequency tunability.