Low RF Power Harvesting Enabled Wireless Sensor Node With Long-Distance Communication Capability

It has been challenging for a wireless sensor node to realize long-range real-time information feedback in the low power harvesting scenarios, due to the limited power budget. In this article, a sensor node powered by low radio frequency (RF) power harvesting is proposed with long-communication capability without using an RF power amplifier or external power source. The proposed sensor node is capable of rectifying input RF power as low as −20 dBm at 433 MHz, while simultaneously generating a 866 MHz second harmonic during the harvesting process. To address problems of long-range data transmission, the generated harmonic is amplified by a tunnel diode powered by rectified dc power, while carrying sensor data of temperature, humidity, and CO2 concentration. The fabricated sensor node shows an output power of around −14.75 dBm for the second harmonic, even with an injecting RF power as low as −20 dBm. It enables a long range exceeding 40 m for indoor communication scenarios with a low energy consumption of just 20.7 mJ. The sensor node demonstrates a great potential for future internet of things (IoT) applications in low RF power harvesting scenarios.