A triple-mode X-band microstrip ring resonator filter

Summary form only given, as follows. This paper presents a low-loss and compact triple-mode ring resonator filter operating at X-band. A classical ring resonator topology with a serpentine line in the middle of the ring as well as perturbations is designed to achieve a third-order response. This filter exhibits insertion loss of 1.67–2.07 dB in the [9.5–10.5] GHz frequency range while return loss is better than 14.7 dB. The 1-dB fractional bandwidth is 13.2%. It provides a footprint reduction compared to standard filter topologies.