Design of Compact Coupled-Line Complex Impedance Transformers With the Series Susceptance Component

In this brief, a compact coupled-line complex impedance transformer (CIT) with a series susceptance component is presented. It is composed of a coupled line and a susceptance component series at the edges of the coupled line. By inserting the susceptance component, arbitrary complex impedance can be transformed and the coupled line has weak coupling coefficient and small impedance value, which shows the feature of compact, easy fabrication and size miniaturization. The design equations for the proposed CIT are derived by using the port voltage-current method combined with the even-odd mode decomposition technology. For verification, two prototypes are designed at 1.0 GHz. The measured results demonstrate that good impedance matching is obtained by the proposed CIT with arbitrary terminal impedances.