Abstract: The design technique for cascaded active filter is mature, but the synthesis of biquadratic circuit is still need to be further studied. Based on the theory of active network synthesis, a method of new active circuit synthesis is given which uses symbolic voltage transfer function and linked infinity variables to describe both Nullors in the nodal admittance matrix and port admittance matrix of a synthesized circuit. The circuit topology is derived by admittance matrix expansion. A new 2nd -order active-RC bandstop filter synthesis example is presented by using privotal expansion on the port matrix. The simulation and the measured results verify the correctness of the given method.

Key words: active network synthesis, Nullor, admittance matrix, bandstop filter

摘要： 级联型有源滤波器的设计技术已经非常成熟，但二阶节电路的综合是尚未解决的难题。根据有源网络综合理论，给出了有源电路新拓扑结构的综合方法。该方法通过给定的电压符号传输函数，使用关联无穷变量来描述被综合电路中节点导纳矩阵和端口导纳矩阵中的零子和任意子，通过导纳矩阵的扩展导出电路的拓扑结构。这种方法可以综合出新的电路结构；给出了二阶有源带阻滤波器新电路的综合实例。仿真和实测结果验证了该方法的正确性。

关键词: 有源网络综合, Nullor模型, 导纳矩阵, 带阻滤波器