Field-Plate Mixer

A novel GaN FET field-plate mixer is presented. The local oscillator (LO) is connected to the FET’s field-plate which is disconnected from the transistor source. The RF/IF input is connected to the gate (RF for down-, IF for up-conversion) and the IF/RF output to the drain. Over the 18-40 GHz range, the mixer cell has an average measured down-conversion loss of 8.8 dB, up-conversion loss of 8.2 dB, IP1 of 10.8 mW/mm and IIP3 of 69.7 mW/mm; values that compare well with the state-of-the-art for passive FET mixers. Good agreement with simulation is demonstrated.