Miniaturized dual-band bandpass filter using defected ground structure

A novel band-pass microstrip filter using defected ground structure (DGS) is proposed. Dual-mode split-ring resonator (SRR) is utilized to form the DGS structure so that different passband can be obtained by different types of dual-mode SRRs, and the center frequencies of the filter is 3.5 GHz and 5.8 GHz, respectively. The first passband contains the whole application frequencies of worldwide interoperability for microwave access and the second passband can be used for radar system. For validating the filter further, a filter based on Roggers RT5880 is fabricated. The measured results agree well with the simulated results. The insertion loss within each passband is less than 2 dB and two transmission zeros are obtained, which meets the engineering requirements, and the overall size of the filter is 20mm×20mm.