Wideband bandstop filter using L-shaped and Quad mode resonator for C and X band application

Abstract

ABSTRACTA wideband bandstop filter (BSF) with a very extensive stop band from 3.52 GHz to 12.38 GHz and a compact size of 7.4 mm × 15 mm (0.27λg × 0.54 λg) for C and X band applications is proposed in this letter. λg is the guided wave length of 50Ω transmission line at center frequency of 8 GHz. Proposed filter has −20 dB fractional bandwidth of 110% with roll-off factor (ratio of 3 dB BW to 20 dB BW) of 0.144. Harmonics suppression is below −20 dB is up to 2f0 (f0 is center frequency). Proposed filter consists of two types of resonator, one Quad mode resonator and other L-shaped resonator. Transmission zero frequency is verified with the help of scattering parameters and transmission line model. The simulated and measured results are in total concurrence with each other.