Microstrip Filters on Co-directional Hairpin Resonators with Split Poles of Operating Attenuation

Circuit engineering methods for increasing frequency selectivity of microstrip filters based on half-wave co-directional hairpin resonators are studied, the principle of operation which is based on the rational use of the effect of inequality of normal wave phase velocities. It is shown that in these structures with N resonators, it is possible to form N + 1 operating attenuation poles at finite frequencies without introducing additional electromagnetic couplings between non-adjacent resonators. The conditions for splitting the operating attenuation poles in compact multiply coupled structures are determined. The results of experimental studies of this type of highly selective filter are presented.