Abstract: A 220 GHz unbalanced tripler based on Schottky varactors was designed. The Schottky varactors were measured to extract parameters for modeling Schottky diodes. A lump equivalent circuit model of Schottky diode was established for 220 GHz tripler circuits design. To reduce the signal transmission loss, a compact suspended microstrip resonator cell (CSMRC) filter structure was introduced to reduce low pass filter circuit length. Since it was difficult to achieve full-wave impedance matching in 220 GHz tripler circuit design, we adopted a method of adjusting impedance matching in overall circuit structure harmonic balance simulation to design a 220 GHz tripler circuit. Finally, the designed 220 GHz tripler was measured and discussed. The experiment shows the output power and efficiency between 213.1 GHz and 221.6 GHz are above 10 mW and 5%, respectively. The maximum output power is 18.7 mW at 218.6 GHz and the maximum efficiency is 8.24% at 217.9 GHz.