5.5 A Stacking Mixer-First Receiver Achieving >20dBm Adjacent-Channel IIP3 Consuming less than 25mW

The sub-6GHz spectrum is used by many standards including 5G New Radio. In this crowded spectrum, an RX requires good linearity and flexibility to address different bands without separate SAW filters, whilst maintaining low NF. Traditional mixer-first receivers (MF-RX) offer this flexibility while postponing voltage amplification to the end of the RX chain, benefiting linearity but leading to relatively poor NF. LNTA-based designs [1, 2] offer an alternative: initial amplification alleviates noise constraints, but the pole at the LNTA output limits the RX operating range, though efforts to reduce parasitic capacitance have been fruitful [2]. Still, linearity is impacted by this initial voltage gain, which is typically addressed by deploying an N-path notch filter in feedback around the LNTA, but its slope is generally limited to 20dB/decade, reflecting in poor adjacent channel IIP3. Although solutions to increase this slope exist, the extra circuitry increases the RF parasitics and power consumption. Also, in contrast to an MF-RX which has a low-ohmic OOB path to ground, the LNTA output stage has to fully absorb any out-of-band (00B) interferer currents.