Low Phase Imbalance D-Band Balun Using 130-nm SiGe BiCMOS Process Suitable for Broadband Differential Circuits

In this paper, we report the design of a D-band modified Marchand balun using IHP's 130-nm SiGe BiCMOS backend process. The design of the balun is based on three asymmetric coupled transmission lines, which reduce the amplitude and phase imbalance. The three asymmetric lines improve the odd mode capacitances, which increase the even/odd mode impedance ratio over wide bandwidth. Thus, wider bandwidth can be achieved with low phase and amplitude imbalance. The balun is EM simulated with ADS momentum and Sonnet. The −10 dB reflection coefficient $(S_{11})$ bandwidth of the balun is 136 GHz. It shows phase imbalance less than 7 degree and amplitude imbalance of ± 1dB from 94 to 177 GHz. Such performances of the balun make it an ideal candidate for various broadband differential circuits.