Analysis and design of impedance-transforming planar Marchand baluns

A technique for designing impedance-transforming baluns is presented in thi s paper. It is based on the Marchand balun with two identical coupled lines . By varying the coupling factor of the coupled sections, a wide range of i mpedance transforming ratios can be achieved. In addition, a resistive netw ork added between the balun outputs is proposed to achieve balun output mat ching and isolation. Microstrip baluns, matched at all ports, for transform ing from a 50-Omega source impedance to 40-Omega as well as 160-Omega load terminations are realized to demonstrate the technique.