Flicker noise in the mixer of a zero-or low-intermediate frequency (IF) wireless receiver can compromise overall receiver sensitivity. A qualitative physical model has been developed to explain the mechanisms responsible for flicker noise in mixers. The model simply explains how frequency translations take place within a mixer. Although developed to explain flicker noise, the model predicts white noise as well. Simple equations are derived to estimate the flicker and white noise at the output of a switching active mixer. Measurements and simulations validate the accuracy of the predictions, and the dependence of mixer noise on local oscillator (LO) amplitude and other circuit parameters.

A new wideband receiver architecture is proposed that employs two separate passive-mixer-based downconversion paths, which enables noise cancelling, but avoids voltage gain at blocker frequencies. This approach significantly relaxes the trade-off between noise, out-of-band linearity and wideband operation. The resulting prototype in 40 nm is functional from 80 MHz to 2.7 GHz and achieves a 2 dB noise figure, which only degrades to 4.1 dB in the presence of a 0 dBm blocker.

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