A 2.4GHz Sub-passive RF Down-converter with Trans-frequency Current-reusing scheme achieving Low Flicker Noise and High Linearity

This paper proposes a radio frequency (RF) down-converter, in which part of the RF transconductance (g
m
) stage is reused as the bias current source of the transimpedance amplifier (TIA) to realize trans-frequency current-reusing, thereby saving 30% power consumption of the down-converter. Other from a conventional passive down-converter, TIA’s DC bias current flows through the mixing switches in the proposed down-converter. Hence it is so called the sub-passive down-converter. Compared with the passive topology where flicker noise from the TIA’s bias is fully fed to the intermediate frequency (IF) output, the flicker noise of the TIA’s current source supplied by the RF g
m
stage is up-converted and filtered out. The flicker noise corner frequency is cut-down to 20KHz, applicable for the zero-IF receiver. The linearity is also improved by the completely counteracting of third-order transconductance from PMOS and NMOS g
m
transistors in the transconductance amplifier (LNTA), which is contributed by their asymmetrical bias current. Fabricated in TSMC 40nm CMOS technology, the sub-passive RF downconverter achieves 55dB conversion gain (CG) and 4dB noise figure (NF), which is suitable for high sensitivity applications. And it implements 23dBm OIP3 at 2.4GHz with 0.8mW power consumption at 0.65V supply voltage and the chip area of 0.3mm × 0.9mm.