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Highly linear receiver RF front-end adopting MOSFET transconductance linearization by linearly superposing several common-source FET transistors in parallel (multiple gated transistor, or MGTR), combined with some additional circuit techniques are reported. In MGTR circuitry, linearity is improved by using transconductance linearization which can be achieved by canceling the negative peak value of gm'' of the main transistor with the positive one in the auxiliary transistor having a different size and gate drive combined in parallel. This enhancement, however, is limited by the distortion originated from the combined influence of gm' and harmonic feedback, which can greatly be reduced by the cascoding MGTR output for the amplifier and by the tuned load for the mixer. Experimental results designed using the above techniques show IIP3 improvements at given power consumption by as much as 10 dB for CMOS low-noise amplifier at 900 MHz and 7 dB for Gilbert cell mixer at 2.4 GHz without sacrificing other features such as gain and noise figure.
Date of Publication: Jan. 2004