An Ultra-Low Power Timing Based OOK Modulation CMOS Transmitter Applied in RF-Powered Temperature Sensor Node

This paper presents an energy-efficient CMOS transmitter (TX) for autonomous temperature sensor nodes. The TX structure is simplified using a frequency divider and power amplifier (PA) with on-off keying (OOK) modulation. A two-stage duty cycle modulator is introduced to significantly reduce power consumption. The 1 st stage controls TX operation between active and inactive modes based on energy availability, while the 2 nd stage compresses the duty ratio during active mode to further reduce operating time. Finally, a 305 MHz TX system is implemented with a standard 0.18 μ ∼m CMOS process. The active area of chip is 0.01 ∼mm². The supply voltage is 1.2 V. Post simulation results indicate that the power consumption of 862 μ ∼W is obtained during data transmission at room temperature. After 1 st -stage modulation (1 active per 63 dis-active), the average power consumption is reduced to 13.7 μ ∼W. After both 1 st and 2 nd-stages modulation (277 pulses with pulse width of 1.5 μ ∼s in 1 s), the ultimate average power consumption reduces to only 5.9 nW. This ultra-low power performance demonstrates good applicability for wireless sensor network (WSN) applications.