A novel compact Ka band fourth-harmonic image rejection mixer

Wth the commercial 0.15-μm pseudomorphic high electron mobility transistor (pHEMT) process, a novel compact Ka-band fourth-harmonic image rejection resistive FET mixer is designed in this paper. A compact Balun with two scale-down Lange couplers used for the impedance transformation is proposed for LO signal pump. The results show that less than 19.5 dB Conversion Loss (CL) in 32~38 GHz, more than 21 dB Image Rejection Ration (IRR) in 32~36.5 GHz, and better than 30 dB and 42 dB high isolation, from LO to RF and 4LO to RF, respectively, can be achieved by the proposed configuration. The chip size is minimized to 1.8 mm×1.4 mm.