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A 0.75mW Receiver Front-End for NB-IoT
This paper presents a sub-mW receiver front-end for Narrowband IoT (NB-IoT) applications. A low-power low noise amplifier (LNA) provides a sub-3dB minimum noise figure (NF) using a transformer with a turns ratio of less than 1 and further improves the linearity and NF using a local feedback and derivative superposition techniques, without any power overhead. Mathematical expressions are presented to enable an optimum choice of a small head resistor in a low-power class-D voltage-controlled oscillator to improve the phase noise and reduce power consumption. A feed-forward technique is proposed in a baseband amplifier to increase gain and reduce the input-referred noise while maintaining linearity. Measurement results of a prototype fabricated in a 65nm CMOS process achieved a sensitivity of -110dBm and an IIP₃ of -5dBm, which meet NB-IoT requirements, all while dissipating 0.75mW.