Ultra-wideband and compact novel combline filters

This paper presents a novel method of designing ultra-miniaturized cavity based combline filter integrable in PCB technology for EMI filtering. Each combline resonator is designed based on concepts of designing a unit cell of metamaterials. The other design steps follow the conventional design procedure of microwave filters. Choice of metamaterial unit cell leads to extreme size reduction and conventional design method results-in optimum number of resonators. A strong inter-cavity coupling value not realizable with conventional evanescent method is realized by TEM section. Therefore, the final structure is very compact and broadband. The design is realized using multilayer planar technology. A design example is provided where a dramatic reduction of the volume of filter by a factor of 7 is obtained.