Compact bandpass filter based on fractal shaped composite right/left handed transmission line with ultra-wide band, deep out-of-band suppression and enhanced passband performance

In this paper, a novel ultra-wide band (UWB) bandpass filter(BPF) based on combined technology has been detailed researched. The proposed filter is constructed by composite right/left handed transmission line (CRLH TL) and Sierpinski carpet shaped six-staged stepped impedance lines for the first time. CRLH TL are mainly consists of Koch loop shaped defected ground structure (KDGS) etched in the ground plane and series capacitive gap in the conductor strip. Equivalent circuit model is put forward and lumped parameters are also extracted for deep insight into the operation mechanism. Consistent results between electrical and EM simulation have confirmed the accuracy of the proposed equivalent circuit model. Simulated results show that the designed BPF with relatively bandwidth 129.4% owns many good performances, i.e., compact in size, relatively low insertion loss(less than 1.5dB) and comparable low return loss (better than 17.2dB) in pass band, deep suppression(better than 60dB) out of band. Thus indicate a giant application in future small size wireless communication system.