A wideband microstrip balun structure

A wideband microstrip balun structure has been proposed, investigated and demonstrated. In contrast to other wideband balun structures, the balun in this paper does not use tight coupled strip lines, transitions (among CPW, CPS, slotline, and double-sided parallel strips) with ground defects, or phase shifters to realize 180° out-of-phase outputs. The proposed wideband balun is based on the higher order mode microstrip line and the 180° out-of-phase and equal magnitude of the balun outputs can be achieved inherently. The experimental results show that the balun has wideband impedance matching, low loss, and excellent amplitude/phase imbalance performance.