Compact highly-selective microstrip filters based on counter-comb structures

This paper examines the design principles of microstrip filters with increased frequency selectivity based on compact structures with a significantly limited number of resonators. It is shown for the first time that in four-resonator counter-comb structures with an additional galvanic connection between adjacent resonators, it is possible to form four working attenuation poles at finite frequencies. The conditions for creating on the basis of these structures microstrip filters with increased one-way frequency selectivity and with a quasisymmetric characteristic are given.