A new linearization technique for CMOS RF mixer using third-order transconductance cancellation

A new third-order transconductance (g(m3)) cancellation technique is proposed and applied to a conventional radio frequency (RF) mixer for improving circuit linearity. The bulk-to-source voltage is applied to adjust the peak value position of g(m3) The cancellation Of g(m3) is utilized by a negative peak g(m3) transistor combined in parallel with a positive peak g(m3) transistor. For a single device, the measured adjacent channel power ratio (ACPR) and third-order intermodulation (IMD3) distortion are both improved over 15 dB. A Gilbert-cell mixer in commercial 0.18-mu m CMOS process was designed using the proposed method to further evaluate the linearity. The compensated g(m3) device is placed in the input RF gm-stage and then reducing the principle nonlinearity source of the mixer. From the experiment results, the ACPR and IMD3 of the mixer are improved about 10 and 15 dB, respectively.