A sub-nW 2.4 GHz Transmitter for Low Data-Rate Sensing Applications

Area of Science:

• Electronics and Electrical Engineering
• Wireless Communication Systems
• Integrated Circuit Design

Background:

• Ultra-low-power (ULP) wireless systems are crucial for emerging applications like IoT and biomedical implants.
• Existing ULP transmitters often struggle with balancing power consumption, data rate, and communication range.
• Efficient energy harvesting and wireless power transfer are key to enabling self-powered wireless devices.

Purpose of the Study:

• To design and demonstrate a narrowband transmitter and antenna system with unprecedentedly low average power consumption.
• To investigate the feasibility of integrating wireless power transfer capabilities within the same system for energy harvesting.
• To optimize the system for both standby and active power efficiency at a 2.4 GHz carrier frequency.

Main Methods:

• A direct-RF power oscillator topology was implemented in a 0.18 µm CMOS process.
• A loop antenna was designed to function as both a radiative element and a resonant component.
• Aggressive power gating and transistor sizing optimizations were employed to minimize standby power.
• On-Off Keying (OOK) and Frequency-Shift Keying (FSK) modulations were supported for data transmission.
• The loop antenna and integrated diodes were utilized for wireless power transfer and system power-up.

Main Results:

• The system achieved an average power consumption of 78 pW at a 1 bps duty-cycled data rate.
• Standby power consumption was reduced to an exceptionally low 39.7 pW at 0.8 V.
• Active-mode power consumption was as low as 38 pJ/bit at a 5 Mbps data rate.
• The integrated antenna and diodes successfully facilitated wireless power transfer for system energy harvesting.

Conclusions:

• The designed narrowband transmitter and antenna system demonstrates a significant advancement in ultra-low-power wireless communication.
• The integrated wireless power transfer capability offers a viable solution for self-powered sensor nodes and energy harvesting systems.
• This design paves the way for highly energy-efficient wireless devices operating in resource-constrained environments.