带抽头的微带交指滤波器初始设计方法繁多,但设计不够全面、简洁,同时精度不高,因此给出了一套详细、简洁的初始设计流程.设计步骤为:指标"规范化",确定低通原型滤波器,求解滤波器阶数,求解归一化电导值,设计抽头的线长和线宽,设计谐振器的线宽,设计非输入输出谐振器的线长,设计相邻谐振器间距,设计输入输出谐振器的线长和抽头的位置,交指滤波器整体建模仿真.最后以Ka波段滤波器为案例进行初始设计,初始设计结果显示中心频率在30.19 GHz附近,通带比29.40～31.00 GHz略大,通带内最大插入损耗为4.22 dB,最小回波损耗为9.32 dB,27.00 GHz和33.40 GHz的带外抑制大于30.00 dB,已经基本满足设计指标,后续只需要稍加优化就能完全满足设计指标,验证了此套设计流程的可行性及其较高的精度.%There are many initial design methods for microstrip interdigital filter with tapped-line but the design methods are not complate,concise and accurate enough,so a set of initial design flow with completeness and conciseness is given.The de-sign steps are as follows:index "standardization",determine the low-pass prototype filter,determine the order of the filter,de-termine the normalized conductance value,design tapped line length and width,design resonator width,design non-input/output resonator length,design adjacent resonator spacing,design input/output resonator length and tapped line position,integral mod-eling and simulation of interdigital filter.Finally,taking the initial design of Ka-band filter as an example,the initial design re-sults show that the center frequency is about 30.19 GHz,the passband range is slightly larger than 29.40-31.00 GHz,the maxi-mum insertion loss is 4.21 dB,the minimum return loss is 9.35 dB,the stopband rejection of 27.00 GHz and 33.40 GHz is more than 30.00 dB,which basically meet the design indexes,only a little optimization is needed to fully meet the design indexes,and the feasibility and high accuracy of the design flow are verified.
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