A Low-Loss 220GHz-325GHz Marchand Balun in 65nm CMOS Technology

This work presents a Marchand balun with three asymmetrical coupled lines operating in the 300GHz band, which is suitable for IEEE Std 802.15.3d (252.72GHz–321.84GHz). Using three asymmetrical coupled lines increases the odd-mode capacitance, which results in the increase of the ratio of even-mode impedance to odd-mode impedance and improvement of the phase and amplitude response. The proposed balun is simulated with Ansys HFSS and fabricated in the 65-nm CMOS process. The simulated amplitude imbalance is less than 1.2 dB and the phase difference between the output ports is from -183° to –178.8°. The measured maximum return loss of the proposed balun is lower than -10dB from 220GHz to 325GHz and the de-embedded average loss is 1.5dB.