新型SCRLH传输线结构在滤波器设计中的应用

Novel SCRLH transmission line structure and its application to UWB filter design

提出了一种新型的简化混合右左手(SCRLH)传输线(TL)结构,并根据周期性理论对该结构的色散和阻抗特性进行了分析,结果表明:该结构在通带内衰减常数为零,并且带内特性阻抗的分布平滑;带外特性阻抗为纯虚数,电磁波传播被抑制.给出了利用该SCRLH TL结构综合带通滤波器的方法,并基于该综合方法设计了中心频率为6.85 GHz、相对带宽约为110%的超宽带带通滤波器,理论分析、全波仿真和实物测量结果吻合良好.

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.