Multiple stage uncompensated Marchand balun with 7:1 bandwidth ratio on double side PCB

Proposed is the design of a multiple stage uncompensated Marchand balun. A coplanar waveguide with a ground plane is used as the coupled line structure providing tight coupling by shielding the centre line from the ground. Wide bandwidth is achieved by the combination of a wideband impedance matching L-section and multiple stages of lambda/4 step transformers. Measurements indicate an approximate -20 dB return loss from 1 to 7.5 GHz, and less than 4deg phase imbalance from DC to 7.2 GHz.