A Wideband Quadrature Power Divider/Combiner and its Application to an Improved Balanced Amplifier

In this paper a novel broadband quadrature power divider and its robust design method are presented. The QPD consists of a two-section power divider in combination with a 90-degree differential phase shifter. The two-section power divider is calculated to provide equal power split, high output port isolation, and good return loss at all three ports. The differential phase shifter consists of a composed right/left handed transmission line and pure-right handed transmission line named CRLHu-TL and PRHd-TL, respectively. The CRLHu-TL is divided into two parts; one of them consists of a pure-left handed section whose parasitic pad effects are represented by means of a pure right handed section named PRHp. On the other hand, the PRHd-TL is composed by a microstrip transmission line of characteristic impedance 50Ω and electrical length 50° and two sections equivalents to PRHp. The proposed circuit is applied to develop a broadband balanced amplifier with measured fractional bandwidth (FBW) of 124.4% at the center frequency of 2 GHz.