A Novel MMIC Balanced FET Mixer with Superior Performance

The design and performance of a new type of monolithic balanced FET mixer is described in this paper. The mixer which measures 3mm × 2.4mm, exhibits at the centre frequency a conversion gain of 2dB (using lOdBm LO power), over 40dB of RF to IF isolation, over 55dB of LO to IF isolation, over 25dB of RF to LO isolation and a ldB compression gain at ldBm of RF input power. The technique employed in the design is to use a common gate/common source FET pair in a conguation which conveniently performs both mixing and balun functions, thus eliminating the need for large and complex balancing circuitry. Active signal combining techniques are also employed in order to maintain a completely active balanced mixer which is capable of providing conversion gain and compactness of size. The excellent measured results have indeed verified the design and so the mixer is suitable for applications in a wide range of monolithic microwave systems and subsystems.