A MMIC Frequency Doubler Using AlGaN/GaN HEMT Technology

A MMIC frequency doubler using the AlGaN/GaN HEMT technology is presented in this letter. At the design frequency of f₀ = 4 GHz and V_DS = 35 V the circuit produced maximum output power of 30 dBm with a conversion gain of 5.5 dB, and maximum conversion gain of 13.8 dB with output power of 23 dBm and output fundamental suppression of more than 11 dBc. The best output fundamental suppression was achieved at f₀ = 4.15 GHz. At this input frequency the circuit produced maximum output power of 28.7 dBm with a conversion gain of 4.5 dB, and maximum conversion gain of 13.6 dB at the output power level of 22.8 dBm with output fundamental suppression of better than 19 dBc. The reason for the better output fundamental suppression at f₀ = 4.15 GHz is the slight mistuning in the high Q shunt resonator in the output network.