Ultra-wideband balun using microstrip to slotline transitions

The design of a compact balun using a pair of microstrip to slotline transitions is presented. The balun is intended to be part of a quasi-Yagi antenna for wideband applications such as microwave imaging. The output port of the balun is in the form of balanced coplanar strip-lines as needed for the quasi-Yagi antennas, whereas the input is a microstrip line. The simulated performance of the designed balun shows more than 10 dB return loss and less than 1 dB insertion loss across the band from 3 to 11 GHz