This paper presents two steps for synthesis when transfer zeros are complexes

the firststep——a ladder network with negative elements is formed by expansion in a method generalized fromBrune’s

the second step——an equivalent network without negative element is derived. The theorem ofladder expansion is given

which analyzes a series of properties in the ladder expansion. This theorem has been proved. Three kinds of equivalent sub-network are given: three-element network

a network without magnetic coupling and Darlington D type network. A series of problems associated with synthesis have been discussed. An example is given for this new method.