Planar realization of a Q-band triple-mode filter using high-order resonances.

A simple method for a Q-band planar triple-mode filter with quasi-elliptic function response is proposed in this letter. This filter is implemented using a high-order mode cavity with substrate-integrated waveguide (SIW) technology and standard printed circuit board (PCB) process. By adopting an orthogonal input and output feed-line and introducing some perturbation, transmission zeros are generated on both sides, which have significantly improved filter selectivity and out-of-band rejection. This triple-mode resonator is then combined with a circular dual-mode cavity to obtain a highly selective filter in Q-band with better stopband rejection. Both of the two filters are fabricated and measured. Low insertion loss and sharp sideband characteristic are observed, which is in good agreement with simulation. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 600–603, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24114 [ABSTRACT FROM AUTHOR]