Design of MMIC Subharmonic Mixer for K-band Receiver Based on 0.25 µm SiGe BiCMOS Technology

A block diagram of K-band SoC receiver frontend (FE) is proposed. It is shown that the use of subharmonic mixer (SM) as well as phase shifter in local oscillator (LO) channel makes possible the implementation of SiGe FE with smaller dimensions. The MMIC SM is designed using singlebalanced topology based on Gilbert cell. To form the quadrature LO signal, a polyphase filter and passive balun are used. In the 18..25 GHz RF frequency band, the 0.25 μm SiGe BiCMOS MMIC SM provides conversion gain of GC = -15..-19.5 dB; return losses at RF and IF ports better than -8 dB; RF-IF isolation better than -14..-27 dB, LO-RF and LO-IF isolations better than -40 dB. The 1-dB compression point for input RF signal is greater than -11 dBm at PLO=18 dBm. Die area of the SM is 1.5×0.9 mm
²
including the pads.