New Chip Enables Ultra-Low Power Wireless Transmission for the Internet-of-Things (IoT)
Recent years have seen a considerable influx of miniaturized interconnected electronic devices for a wide range of applications (e.g., connected-health, smart-homes, smart-cities, etc.) collectively referred to as the Internet-of-Things (IoT). Low power consumption is critical to extending battery lifetimes in these devices, often limited by the wireless transmitter. 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 (RF) 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.
This had posed a longstanding technological hurdle when one wanted to push power consumption down to the ultra-low power regime because, with well-established frequency synthesis techniques, lower power was associated with a compromise in accuracy and robustness. 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 of these, while achieving the best energy-efficiency (67 pJ/bit) and lowest power (67 µW) among reported sub-1mW narrowband transmitters, which is quite remarkable! 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 Radio Frequency Integrated Circuits Symposium, held virtually in 2020.
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.