The Internet of Things may soon become more efficient thanks to researchers at the Center for Wireless Communications who recently overcame a longstanding technology hurdle to develop a new circuit technique for achieving ultra-low power wireless transmission while maintaining accuracy and robustness.

Over the past few years, the Internet of Things (IoT) has seen a considerable influx of miniaturized interconnected electronic devices for a wide range of application areas, such as connected health, smart homes, and smart cities, many of which require low power consumption as a critical component for extending battery lifetimes. However, this feature is often limited by the wireless transmitter in these devices. Contrary to conventional radios used in cell phones that communicate with base stations located miles away, many IoT transmitters only need to communicate over a short range (~1-2 meters) to a nearby base station, such as a smartphone or a smartwatch. Because of this, the power amplifier that drives the antenna is no longer power hungry. Instead, the frequency synthesizer generating the radio frequency  carrier is the power bottleneck. 

Like conventional radios, the synthesizer must maintain frequency accuracy irrespective of variation due to manufacturing, supply voltage, and environmental temperature.  For years, this has posed a longstanding technological hurdle to achieving ultra-low power consumption because well-established frequency synthesis techniques typically associate lower power with a compromise in accuracy and robustness. However, recently researchers at the Center for Wireless Communications led by Prof. Drew Hall developed a new circuit technique to overcome this hurdle. Their prototype chip demonstrates excellent robustness to process variation, consistent performance across -30 to 90 ºC, and complete insensitivity to voltage variation – all while achieving the best energy efficiency (67 pJ/bit) and lowest power (67 µW) reported among sub-1mW narrowband transmitters. This work on a 400 MHz MedRadio transmitter with state-of-the-art ultra-low power was presented by UC San Diego alumnus Dr. Somok Mondal (Ph.D. '20) at the 2020 Radio Frequency Integrated Circuits Symposium.

Paper: S. Mondal and D. A. Hall, "A 67-μW Ultra-Low Power PVT-Robust MedRadio Transmitter," 2020 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), 2020, pp. 327-330.