Tri-notched Ultra-wideband Bandpass Filter Design Using FMMR, CSRR, DGS and Inter-Digital Couples

A folded multiple-mode resonator (FMMR) with complementary split ring resonator (CSRR), defected ground structures (DGS) and inter-digital couple is introduced for ultra-wideband bandpass filter design in this paper. The wider bandwidth (3.1 to 9.8 GHz) with FBW = 126 %, lower insertion loss (0.26 dB), and higher rejection level (-44 dB) of UWB band at central frequency f0 = 5.6 GHz are presented. By using the CSRR and inter-digital couple, three notch responses can exist in the UWB passband for blocking the interference signals. Adjusting the size factor of CSRR and inter-digital couple, the wide tuning ranges of notch frequencies included the desired frequencies of 5.18/6.10/8.08 GHz are achieved. The wide tuning ranges of two notch frequencies cover from 5.0 GHz to 8.4 GHz. It is a simple way to control the notch response.