Ladder wave digital filters realizing complex attenuation poles

It is known that for wave digital filters (WDF) either their transmittance or their reflectance can be used as transfer function. So far, only the first possibility has been examined in detail. However, if a WDF is derived from a reference ladder network composed of inductances, capacitances, and/or unity elements, complex attenuation poles (transmission zeros) cannot then be obtained. It is shown in this paper that one can design a ladder WDF using the reflectance in order to obtain attenuation poles at complex frequencies. The sensitivity characteristics of a filter designed in this way are also presented.