A LNA-merged RF front-end with digitally assisted technique for gain flatness and input-match compensation

In this paper, a wideband LNA-merged RF receiver front-end (RFE) with digital assist (DA) for conversion gain flatness and input-match compensation is presented. It employs a novel common gate g_m-stage with multiple feedback, double-balanced Gilbert-type switches and active loads to form stacking topology. The conversion gain boost factor and input-match compensation factor can be controlled by DA. Theory and simulation results show that DA broaden the RF bandwidth of the proposed RFE and improve the conversion gain flatness. A prototype of the presented RFE is designed and fabricated in the SMIC 40-nm CMOS process, the active area is just 0.03mm2. From measurement results, the proposed RFE achieves conversion gain of 7.5 dB, 10.0 dB and 12.5 dB from 0.5 to 3.5 GHz with 0.3 dB inband ripple. The best IIP3 is 1.5 dBm. The minimum SSB NF is 11.3 dB. The average DC power is only 3.2 mW from a 1.1 V supply.