On the improvement of planar multisection balun

A planar multisection-coupled line balun is presented. The design is based on the cascaded quarter wave coupled line. The even and odd mode impedances are chosen to provide very high even impedance. In this paper, the layout of the circuit is optimized for maximum operating bandwidth. The balun characteristics are 0.5 db amplitude balance with 2.8 GHZ center frequency and 39% bandwidth. The balun is fabricated on FR-4 and measured. Measurements are in very good agreement with simulated data.