Microwave filters with increased frequency selectivity based on quarter-wave hairpin resonators

This work examines new designs of planar four-resonator filters based on counter-comb structures with quarterwave hairpin resonators. It is shown that in such structures it is possible to generate a significant number of working attenuation poles, exceeding the number of filter resonators. The mechanisms of generation of these working attenuation poles and their interrelation with geometrical parameters of structures are considered. The results of electrodynamic simulation of microstrip filters are presented, which are realized on substrates with different values of the relative permittivity ε
_r
=9.8 H εr=80. It is noted that these structures can be used as a schematic basis for creation of compact highly-selective microstrip filters with a limited number of resonators.