具有多传输零点的微带传输线滤波器设计

提出一种非对称两腔发夹型滤波器的设计方法. 应用传输矩阵分析了2种串联传输线型谐振器与传输响应零点之间的关系,依据奇偶模激励法得出了并联耦合型传输线滤波器的传输响应公式,结合这些特点,设计了一种可以产生3个传输零点的两腔滤波器,在含源负载交叉耦合的情况下,突破了现有滤波器N个谐振器才能产生N个传输零点的局限,进一步提高了滤波器的频带选择特性.实测结果验证了该方法的正确性.

Design of a Microstrip Transmission Line Filter with Transmission Zeros

A design method for asymmetric two-cavity hairpin filter is proposed. Firstly, by using transmission matrices, the relation between the types of serial coupled microstrip transmission line and transmission zeros of transfer response is analyzed. and then, the transmission response formula of the parallel-coupled transmission line filter is derived through even and odd-mode excitations. The serial and parallel microstrip line structures are applied to the design of a two-pole microstrip hairpin filter with asymmetric feed. A N-order cross coupling network with source-load coupling can realize a maximum number of transmission zeros that can equal to N. Compared with source-load coupling, the new two-pole hairpin filter which can obtain three transmission zeros has improved selectivities. A good agreement between measured and simulated data has been reached.