Performance and Large Signal Modelling of a GaAs Heterojunction Bipolar Transistor Mixer at 950MHz

A GaAs heterojunction bipolar transistor (HBT) single ended active mixer is discussed. Simulations are performed using a large signal HBT model. A novel way of incorporating the d.c equations of an HBT into a large signal simulator is described. Both conversion gain and intermodulation properties are predicted to within ±3dB of measured values. The measured intermodulation performance of the device in a tuned state is superior to both a resistive MESFET and HEMT mixer.