Gain, Signal-to-Noise Ratio and Power Optimization of Envelope Detector for Ultra-Low-Power Wake-Up Receiver

This brief considers the design of an envelope detector for the front-end of a wake-up receiver. A design procedure that allows to optimize the trade-offs between gain, signal-to-noise ratio and power consumption is proposed. It is based on the analysis of the envelope detector in all inversion regions. Two novel figures of merit that only depend on the inversion level are proposed to aid the design. The predictions are verified against simulation and measurements results, both at the transistor and complete circuit level. An arrangement for the bias circuitry of the wake-up receiver front-end is proposed that leads to an intrinsic bandpass characteristic that improves the signal-to-noise ratio. A prototype integrated circuit, in a 130 nm CMOS process, of a fully integrated wake-up receiver front-end for the 2.4 GHz band was designed based on the presented approach and measured. The results show a remarkable conversion gain with a scaling factor of 9800 1/V with a current consumption of 100 nA from 1.2 V at 12 dB signal-to-noise ratio and -48.5 dBm sensitivity.