Low-phase error and high isolation CMOS active balun

In this paper, a C-band active balun is demonstrated in a standard 0.18-µm CMOS process. Based on the proposed phase-correction technique (PCT) and the bridged-T network (BTN), the balun features low-phase error and high isolation, respectively. The PCT is based on a three balun topology, and the BTN is formed by the output matching networks and an isolation resistor. The balun consumes 1.8 mW from 1.2V-supply voltage, and features a peak gain of 4.6 dB at 4.6 GHz. The measured isolation is better than 18 dB, and the phase error is less than 1.6° from 4.6 GHz to 5.7 GHz.