Passive broadband millimetre-wave uniplanar MMIC balun

A new uniplanar monolithic microwave integrated circuit (MMIC) balun using lumped circuits is presented. The proposed planar balun consists of a wideband Wilkinson power divider and a broadband 1808 phase shifter using novel series and parallel LC reflective terminating circuits. To demonstrate the design methodology, a 24-44 GHz MMIC balun was realised as a 1.4 mm(2) GaAs chip. The measured return losses for the unbalanced and balanced ports are better than 212, 210 and 27 dB, respectively. The measured amplitude and phase imbalance between the two output ports are less than 0.5 dB and 78, respectively, and maximum insertion loss is 5 dB.