Design of a 12-40GHz MMIC doubler with 50dBc fundamental isolation

In this paper, an ultra-broadband frequency doubler based on 0.1um GaAs pHEMT process is proposed. Double-balanced structure is applied in this doubler, which consists of rectifier bridge composed of four Schottky diodes and two balanced baluns. The whole circuit is optimized to achieve highest fundamental isolation. The simulation results indicate that this doubler has quite flat output curve, within 12 to 40 GHz, the conversion loss is less than 14dB under the excitation signal of 18dBm power level. The fundamental isolation is above 50dBc, third harmonic is also better than 40dBc in the entire band.