1/f noise in passive CMOS mixers for low and zero IF integrated receivers

Passive mixers are generally thought attractive as having no 1/f noise sources when used in AC coupled configurations, in contrast to the conventional "Gilbert" type circuit. In this paper, we show that not only does this type of mixer exhibit internal 1/f noise, but with a poor choice of device sizes, one can magnify the noise of a subsequent amplifier stage. The mechanisms underlying these phenomena are examined, and some design recommendations offered.