Comparing active Gilbert mixers integrated in standard SiGe process (Part Ⅱ)

摘要

In Part Ⅰ, which appeared in the January 2005 issue, mixers designed with the Gilbert cell were introduced. Parameters that affect the performance of the Gilbert cell and the mixer were examined. Part Ⅱ summarizes the performance of the mixers relative to changes in the parameter using the same process in all mixer designs. The mixers presented here have been designed to downconvert an 8 MHz bandwidth signal from RF (1800 MHz) to an intermediate frequency (IF) of 40 MHz. The local oscillator (LO) frequency is 1840 MHz. The fabrication process used to make the mixers is a standard 0.8μm SiGe process. Among active mixers the most common schema is the Gilbert cell. The first mixer is a Gilbert cell that has been optimized to obtain low noise. It is called mixer NF in this article. The second and the third mixers are Gilbert cells designed to improve linearity, using two different methods: emitter degeneration and class AB RF input stage, respectively. The mixer called mixer Ze is a Gilbert cell with emitter degeneration. In the mixer called mixer AB, the class AB has been used as the amplification stage.