On-chip tri-band bandpass filters using square ring open-stub loaded resonator on GaAs substrate

The design and fabrication of novel on-chip tri-band bandpass filters using square ring open-stub loaded resonator are presented. The open stub-loaded transmission line is introduced to produce tri-band characteristic and improve band-to-band isolation. Theory analysis indicated four transmission zeros can be obtained and independent controlled three central frequencies give the structure more convenience and flexibility. To validate the proposed structure, a tri-band bandpass filter centered at frequencies of 1.8 GHz, 2.4 GHz, and 3.5 GHz on GaAs substrate is designed and fabricated. The measured results are in good agreement with the simulated results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1958–1961, 2016