A comparison of bipolar and CMOS mixer structures for direct conversion modulation at microwave frequencies

The mixer is one of the fundamental circuit blocks of any wireless communication system. Most portable communication systems have at least two mixers, one in the receiver and another in the transmitter. Although high performance bipolar and CMOS mixers have been available for some time, their implementation is still a challenging subject for high frequencies, low-voltage and low-power circuit design. In this paper double balanced mixers performing direct conversion modulation are studied. The problems of noise and non-linearities are also addressed.