利用数字信号处理理论,设计不等带宽晶体型交错滤波器。运用琼斯矩阵理论计算晶体型交错滤波器的光谱透射率表达式, 在此基础上利用数字信号处理中的Z变换方法对其进行简化, 使其满足有限脉冲响应（FIR）表达式, 继而利用数字信号处理中的FIR理论设计不等带宽型交错滤波器。其中晶体和检偏器的偏角根据系统光谱透射率的表达式反向推解求出。设计了窄口和宽口输出谱3 dB处带宽比为1∶2的50 GHz不等带宽交错滤波器, 并给出了宽口和窄口输出光谱在0.5 dB处带宽宽度、隔离度和陡度的各组参数; 比较了在同种阶数下运用不同FIR设计所得的结果, 分析了不同方法对于输出透射光谱波形特性的优缺点。

Asymmetrical birefrigent crystal interleaver is designed by using digital signal processing theory. Based on Jones-matrix theory, the expression of the system composed of several cascaded crystal wave plates located between a polarizer and an analyzer is calculated, and it is simplified to make the output frequency response satisfy the expression of FIR by using Z transform. Using FIR digital filter design technique, an asymmetrical interleaver is designed. The azimuth angles of crystal and analyzer are determined by using step-down iteration method based on the expression of spectral transmittance. An asymmetrical 50 GHz interleaver is designed, the ratio of one output port (narrow bandwidth) to another output port (wide bandwidth) at 3 dB passband is 1∶2. The design examples of three crystals structure using Equiripple method are given. The bandwidth at 0.5 dB passband,channel isolation and gradient in both wide port and narrow port are given. Three design results respectively got by three different FIR design methods in the same order are compared, and the advantages and drawbacks of different methods are analyzed.