A full-wave EM approach of sub-harmonic mixer design using 3D diode model and extracted parameters

The design of a low-cost microstrip based sub-harmonic mixer (SHM) is presented, which is feasible to be integrated with other circuit stages on the same substrate because of its good S11s. Taking the often neglected S11s as one of the goals for the mixer, this paper utilizes a 3D diode model and quasi-linear parameters to model the schottky barrier diode in the full-wave EM simulator HFSS, which is more accurate on predicting S11s compared to the non-linear approach using circuit simulator and SPICE model. As a verification, an SHM that works at RF of 88 to 100 GHz and LO of 42 to 48 GHz is designed, fabricated and measured. Measured S11s are below -10 dB and agree well with simulated prediction. In addition, the measured conversion loss is below 14 dB under different LO frequencies, demonstrating that the mixer is able to work at a wide band of LO.