Design of low flicker noise active CMOS mixer

Abstract

With the development toward an integrated single-chip multi-standard radio receiver, a DCR (Direct Conversion Receiver) is usually preferable due to its low power consumption and low manufactory cost. Backward compatibility to narrow band standards such as GSM/EDGE is also important to avoid possible service interruption. However, the excess flicker noise in modern CMOS technology degrades the DCR sensitivity in narrow band radios. Flicker noise which has most of its power centered in the low frequency band is first introduced to the receiver by the mixer and the degraded noise figure can not be restored by any subsequent amplification or processing. Thus, it is critical to reduce the mixer flicker noise for narrow band applications. In this paper, the flicker noise coupling mechanism in an active CMOS mixer is analyzed and circuit techniques are proposed to significantly lower the mixer’s flicker noise.