Miniaturized matched band-stop filter based dual mode resonator

Band-stop filters are very important components for microwave transceivers. Wireless communication systems, the current application usually require small devices to fulfill the miniaturization requirements of mobile unit. Various methods for this point have been proposed for band-stop filters implementation involving the use of shunt stub with large circuit. The conventional band-stop filter reflects stop-band signals, and resonator with finite Q tends to reduce and limit their stop-band attenuation. Recently, new filter topology using a lossy resonator has been introduced. The shortcoming of such type of filter is its large size because it is using second order resonator to produce single notch with infinite attenuation. In this paper, a novel technique to construct a miniaturized matched band-stop filter Based dual mode resonator which is compact and matches at all frequencies is introduced. It is achieved by incorporating the stepped impedance dual-mode resonator into the matched band-stop topology. The proposed technique results in 50 % size reduction compared with the dual-mode ring resonator that has an electrical length of 360°. In addition for the short electrical length of the proposed technique the first spurious resonance occurs at 4.7 times the fundamental resonance frequency.