Planar ultra-wideband balun using coupled microstrip lines

摘要

A planar balun based on using parallel-coupled microstrip lines is presented. It is designed to transfer the unbalanced microstrip line to a balanced coplanar stripline as needed in many applications such as centre-fed dipole antennas. The balun includes a T-junction of stepped-impedance and tapered microstrip lines and two pairs of stepped-impedance parallel-coupled lines. The designed balun covers the band from 3 to 11 GHz with less than 0.4 dB insertion loss.