To determine a Gilbert mixer’s frequency response for each local oscillator (LO), RF, and intermediatefrequency (IF) stage, a measurement approach has been proposed by Jin-Siang Syu, Chinchun Meng, and Chih-Kai Wu from Taiwan’s National Chiao Tung University. Guo-Wei Huang from National Nano Device Laboratories also took part in this work. The researchers demonstrated wideband downconversion mixers using a 0.35-µm silicongermanium (SiGe) heterojunction-bipolar-transistor (HBT) and a 2-µm gallium-indium-phosphide (GaInP)/gallium-arsenide (GaAs) HBT.

The SiGe HBT micromixer achieved conversion gain of 6 dB, IP₁ dB of –17.5 dBm, and an input third-order intercept point of –7 dBm with a 3.3-V supply voltage and power consumption of 37.5 mW. In contrast, the GaInP/GaAs micromixer achieved conversion gain of 25 dB, IP₁ dB of –25 dBm, and a third-order intercept point of –15 dBm with the 5-V supply voltage and 50 mW of power consumption. See “Comparison of Wideband Gilbert Micromixers Using SiGe HBT and GaInP/ GaAs HBT Technologies,” Microwave And Optical Technology Letters, September 2008, p. 2254.