Broadband balun for monolithic microwave integrated circuit application

We present a compact and broadband balun based on the concept of a synthetic left-handed transmission line and right-handed transmission line.The compact balun uses lumped, discrete LC elements only to reduce the circuit size dramatically. For the frequency range of 0.6-1.2 GHz, this circuit maintains 180 ± 9.5° phase difference at the outputs, whereas the maximum insertion loss is -1.78 dB, and the minimum return loss is -10.2 dB at all three ports, yet the circuit size is merely 12 × 8 mm². As far as we know, this is the smallest broadband balun reported in the literature, and the size can be further reduced, if the circuit is made with a monolithic microwave integrated circuit technology.