集成串联环型谐振光滤波器特性的数值分析

Characteristic Analyses of Series-Coupled Multiple-Ring Resonator Filter

将串联结构的环型谐振滤波器类比为四端口网络,利用传输矩阵法推导出通路和下话路传输函数的通用公式。对表征串联双环谐振滤波器响应的特性参量:幅度平坦性、通带带宽、相位群时延进行了数值计算和优化设计。结果表明:尽管损耗将引起滤波响应幅度的轻微降低,但在目前改善了的制作工艺下,损耗对器件的影响可以忽略;滤波器的传输特性主要由环与环间耦合系数决定,通过优化使其从中间到两侧对称增加,可以在实现滤波响应最大平坦性的同时,改善通带带宽和过渡带的滚降特性。与单环结构相比,不仅幅度特性得到了明显的改善,而且消除了二阶群时延色散效应。

By introducing the equivalent four-port network, the general formulas for the series-coupled multiplering resonator were derived with the transfer matrix method. The characteristic parameters of series-coupled doublerings resonator such as, amplitude flatness, bandwidth and phase group delay, were analyzed and optimized. Numerical results demonstrated that the propagation loss on the device was negligible with improved fabrication techniques. Since filter performances were determined by the coupling coefficients, the maximal flat response with sharper rolloff could be achieved by setting coupling coefficients symmetric and smaller in the middle. Compared with single-ring resonator, the series-coupled multiple-rings structure obviously improved the amplitude response and eliminated the second-order group delay dispersion.