A compact millimeter-wave broadband stacked coupled balun

This paper presents a compact 27.6-65.5GHz broadband Marchand balun in a 65-nm 1P6M CMOS technology. It uses stacked coupled structure for millimeter-wave application. The stacked coupled structure uses different layers coupling signals, instead of a planar layer, to reduce Machand balun size The balun bandwidth is 81.2%, the amplitude imbalance is less than 0.8 dB, and the phase imbalance is less than 8°. The balun occupies a 0.12mm
²
die area.