Quasi-lumped-open-loop suspended stripline bandpass filters

In this paper, a combined quasi-lumped-open-loop resonator (QT-OLR) is introduced and applied for filter design. The resonator can have single and dual-band behavior. Two bandpass filters as well as two dual-band bandpass filters have been designed, fabricated, and tested, that consist of two resonators each. The bandpass filters show the behavior of four return loss poles (fourth order filter), and by slitting these resonators a dual-band bandpass filter can be achieved (each band has two return loss poles). Transmission zeroes can be easily introduced into the filter response as well by utilizing the properties of both quasi-lumped and open-loop resonators.