A High Conversion Gain 210-GHz InP DHBT Sub-Harmonic Mixer Using Gain-Enhanced Structure

In this paper, we present a novel gain-enhanced sub-harmonic mixer based on 0.5-μm emitter width InGaAs/InP double heterojunction bipolar transistors (InP DHBTs). The proposed mixer consists of a transconductance stage and a gain-enhanced stage. A common-emitter transistor is used in the first stage to realize the sub-harmonic mixing while another common-emitter transistor is used in the second stage to remix the f
_LO+IF
and fIF and also amplify the f
_2LO+IF
. For further verification, a transconductance mixer and a gain-enhanced mixer were designed and fabricated. Compared with the transconductance mixer, the gain-enhanced mixer exhibits a 6.8-dB higher conversion gain with 2-dB lower LO input power and a peak up-conversion gain of 9 dB at 213 GHz with f
_IF
= 1 GHz, f
_LO
= 106 GHz, and P
_IF
= -26 dBm P
_LO
= 3 dBm. To our best knowledge, the gain-enhanced mixing structure is proposed for the first time.