A New Linearization Technique for CMOS RF Mixer Using Third-Order Transconductance Cancellation

Dept. of Electr. Eng., Nat. Central Univ., Jhongli
IEEE Microwave and Wireless Components Letters (Impact Factor: 1.78). 06/2008; DOI:10.1109/LMWC.2008.922129
Source: IEEE Xplore

ABSTRACT A new third-order transconductance (gm3) 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 gms. The cancellation of gm3 is utilized by a negative peak gm3 transistor combined in parallel with a positive peak gm3 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-mum CMOS process was designed using the proposed method to further evaluate the linearity. The compensated gm3 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.

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