Low-loss and compact millimeter-wave balun on Si

We designed and fabricated low-loss and compact microstrip line and Marchand balun composed of thick Cu and thick resin on Si substrate for millimeter-wave applications. An attenuation constant α and Q of the fabricated microstrip line are 0.17 dB/mm and 52 at 60GHz, respectively. The insertion loss and the core size of the fabricated balun are 0.6 dB at 60 GHz and 300 µm × 450 µm, respectively, which are the lowest and the smallest among the millimeter-wave baluns ever reported, to our knowledge.