Investigations on improving the spurious performance of a coaxial combline filter

Miniature bandpass filter with a wide stopband up to 40F0

“…Defected ground structures and slotted ground structures allow realizing wide stopband in planar bandpass filters as well [8, 9]. Combined and capacitively loaded interdigital filters [10] as well as stepped‐impedance coaxial resonator filters [11–13] are also used to design device with wide rejection band.…”

Novel Microstrip Fed Mechanically Tunable Combline Cavity Filter

“…Therefore, various tunable filter topologies have been reported [3], [4] including electronically and mechanically tunable combline filters (MTCFs) [1]- [9], the latter still widely preferred owing to good filter performance, linearity, low loss, low cost and good spurious response. Electronically tunable combline filters can provide high tuning speeds and can be electrically small when realized in printed form [1], [5].…”

“…On the other hand, low tuning speed, relatively bulky size and heavy weight (at low frequencies), integration with other printed circuits and manufacturing difficulties associated with both the coaxial to cavity matching section and the small sized resonators (especially at high frequencies) appear as the main problems of MTCFs. Therefore, several studies have been reported to address these problems using quasi-planar realizations [6], and microelectromechanical systems (MEMS) technology [7], [8], as well as to improve their spurious performance [9]. In this letter we propose a novel microstrip fed mechanically tunable combline cavity bandpass filter.…”