A novel SCRLH transmission line structure and its application to UWB filter design

In this paper, a novel simplified composite right/left-handed (SCRLH) transmission line (TL) structure is proposed. The dispersion and impedance characteristics of the novel structure are first analysed based on Bloch-Floquet theory, which shows that the attenuation constant keeps zero with a relatively smooth characteristic impedance distribution within the passband and that the characteristic impedance is purely imaginary with the inhibition of the electromagetic wave propagation outside the passband. Based on the above analysis, the methodology of synthesizing bandpass filter by utilizing the novel structure is further proposed, which is then adopted to design a UWB filter with the center frequency located at 6.85 GHz and the fractional bandwidth of 110%. A good agreement among the circuit simulation, fullwave simulation and experimental results justifies the theoretical analysis and the synthesis method presented in the paper.