基于分形特征和双层光子带隙结构的宽阻带低通滤波器

A low-pass filter of wide stopband with a novel dual-layer fractal photonic bandgap structure

提出一种新颖的基于分形特征和双层光子带隙 (PBG)结构的宽阻带低通滤波器 .该滤波器在接地板上刻蚀一阶SierpinskicarpetPBG结构 ,在顶层微带线与接地板之间增加一层具有三阶SierpinskigasketPBG结构的金属层 ,该金属层经过打通孔与接地板连通 .这种双层PBG结构的低通滤波器 ,具有良好的宽阻带特性 ,且电路尺寸小、结构紧凑 .对比了单层普通方孔PBG结构的低通滤波器、单层一阶SierpinskicarpetPBG结构的低通滤波器和双层分形PBG结构低通滤波器的传输特性 ,同时给出FDTD模拟和实测结果 .结果表明 ,该低通滤波器在低通频带内 (5 0MHz— 3GHz) ,信号的传输系数S2 1 达到了 - 3dB以上 ;在阻带内 (3— 2 0GHz) ,信号的传输系数S2 1 均低于 - 2 0dB ,因而具有良好的宽阻带特性 ,其传输特性优于其他两种PBG结构的低通滤波器 .

The concept of the photonic bandgap (PBG) is extended to a novel architecture which consists of two fractal PBG plates stacked up in the direction perpendicular to the plane of the substrate. This novel, dual-layer fractal PBG is presented here as the substrate for a microstrip line, and the resulting configuration builds a low-pass filter of wide stop-band. In the specific design, the dual-layer PBG includes two kinds of fractal PBGs with different periodicities in which one fractal PBG consists of a first-order Sierpinski carpet, and the other consists of third-order Sierpinski gasket. Simulated and measured transmission parameters in comparison with the corresponding two filters with monolayer PBG show that the filter with the proposed fractal PBG drastically enhances the width of the stop-band.