A SAW-Less 2.4-GHz Receiver Front-End with 2.4-mA Battery Current for SoC Coexistence

A 2.4-GHz receiver for short-range communications with +6 dBm out-of-band IIP3 and only 2.4-mA battery current is presented. The single-ended input is coupled through an integrated transformer to a push-pull differential low-noise transconductance amplifier (LNTA) followed by a current mode passive mixer that drives a single-opamp biquad trans-impedance amplifier. This approach ensures sufficient linearity to enable coexistence with large out-of-band interference arising from other on-chip/on-board transceivers. An efficient block stacking technique is proposed to minimize the current drawn from a standard 1.8-V supply. The first stages of the two opamps used in the I and Q baseband Rauch filters are placed above and below the LNTA core, thereby sharing its dc current. Two active inductors isolate the RF and baseband signal paths. Several techniques are used to limit the impact of the 1/f noise of the RF blocks on the receiver and to minimize nonlinearities due to interactions between blocks sharing the same current. The entire receive signal path draws 2.4 mA from a 1.8-V supply and has a noise figure of 7.8 dB at 2.4 GHz and an out-of-band 1-dB compression point of -5 dBm. The chip, implemented in 28-nm LP CMOS, occupies an active area of 0.4 mm2