Abstract:

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 the Bloch theory, which shows that the attenuation constant remains zero with a relatively smoother characteristic impedance distribution within the passband and that the characteristic impedance is purely imaginary with inhibition of the electromagetic wave propagation outside the passband. Based on the above analysis, the methodology for synthesizing the bandpass filter by utilizing the novel structure is further proposed, which is then adopted to design an ultra-wideband (UWB) filter with the center frequency of  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.

Key words: simplified composite right/left transmission line (SCRLH TL), dispersion, impedance characteristics, bandpass filter synthesis, ultra-wideband (UWB)