An Ultra-Low-Power Low-Voltage WuTx With Built-In Analog Sensing for Self-Powered WSN

This paper presents an ultra-low-power, low-voltage wake-up transmitter (WuTx) capable of transmitting two sensors' analog output simultaneously using short pulses that their LOW and HIGH time are modulated with the analog inputs. A subthreshold relaxation oscillator along with an ultra-low-power comparator and voltage reference creates a baseband signal modulated based on two input analog signals, a ring oscillator upconverts the baseband signal to the desired transmission channel frequency (915 MHz or 2.4 GHz), and finally, an efficient Class E power amplifier with variable output power drives the antenna. The minimalist design of the proposed transmitter avoiding power-hungry data converters for sensor readout circuitry and modulation, short pulses at the output that enable the power amplifier for a short time during transmission along with the operation in the subthreshold region significantly reduces the overall power consumption. The proposed low-power and low-voltage transmitter is ideal for the long-term deployment of self-powered wireless sensors when the voltage gain and efficiency of harvesters are limited. Fabricated in a 65nm standard TSMC CMOS process, the proposed transmitter consumes a minimum of 5.41μW average power when it is on while delivering the output power of -1dBm and 7nW when it is completely off.