Wideband balun and impedance transformers integrated in a four-layer laminate PCB

Transmission line balun and impedance transformers are described. They were realized as part of a four-layer laminate PCB using a planar, quasi-coaxial transmission line structure. Approximately a decade bandwidth was achieved, with operating frequencies in the lower and sub gigahertz range. Both transformers employ the same planar coil geometry, each covering an area of less then 0.6 cm². The transformers can be used in medium power applications as their power handling capability is merely limited by the planar transmission lines.