A GaAs p-HEMT Distributed Drain Mixer With Low LO Drive Power, High Isolation, and Zero Power Consumption

This paper presents a balanced distributed drain mixer fabricated in a 0.25-mu m GaAs p-HEMT technology. The balanced distributed mixer combines two single-ended distributed mixers with an on-chip RF balun and LO divider integrated for improving isolation performance. Each single-ended mixer is designed with three drain-mixing unit cells distributed along transmission lines for broadband operation. The transistor size, bias condition and transmission line lengths are analyzed and determined to improve the conversion gain, bandwidth and impedance matching. In addition, the LO drive power required for mixing operation is reduced by bias optimization and large-signal LO matching. The balanced distributed drain mixer exhibits measured conversion gain of -4.0 to -7.4 dB from 5.4 to 21.8 GHz. The LO drive power of the mixer is as low as 2 dBm. The LO-to-RF and LO-to-IF isolation are higher than 23.5 and 54.7 dB, respectively. The mixer consumes no dc power due to the passive drain-mixing topology.