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Herein, design, development, and analysis of ultra-low power sensing energy harvesting modules and their subcomponents for ISM band applications have been studied with a holistic approach in an effort to achieve a feasible and high efficient RF energy harvesting performance. The complete harvester system designed and developed here consists of a zero-bias RF energy rectifying antenna (rectenna), DC boost converters and energy storage super-capacitors. Compared with the counterpart energy sources, the surrounding or transmitted wireless energy has low intensity which requires designs with high efficiency. To achieve a successful harvester performance, rectifier circuits with high sensitivity Schottky diodes and proper impedance matching circuits are designed. Dedicated RF signals at various levels from nanowatts to miliwatts are applied at the input of the rectenna and the measured input power versus the scavenged DC output voltage are tabulated. Furthermore, by connecting the rectifier to a high gain antenna and using a RF signal transmitter, the wireless RF power harvesting performance at 2.4 GHz was tested up to 5 m. The performance of the rectenna is analyzed for both low-power detection and efficiencies. Impedance matching network is implemented to reduce the reflected input RF power, DC to DC converters are evaluated for their compatibility to the rectifiers, and super-capacitor behaviors are investigated for their charging and storage capabilities. The measured results indicate that a wide operating power range with an ultra-low power sensing and conversion performance have been achieved by optimizing the efficiency of the Schottky rectifier as low as −50 dBm. The system can be used for battery free applications or expanding battery life for ultra-low power electronics, such as; RFID, LoRa, Bluetooth, ZigBee, and low power remote sensor systems. K E Y W O R D S rectenna, RF energy harvesting, Schottky diode, ultra-capacitor, wireless power transfer 1 | INTRODUCTIONThe harvested RF energy is a potential solution for low power wireless communication networks and can increase battery life or allow battery-free operations. ISM/SRD (Industrial, Scientific and Medical/Short Range Devices) applications typically utilize low power wireless RF communication modules, such as ZigBee, Bluetooth, and RFID. RF Energy Harvesting applications require long-lasting and low profile circuits and limited environmental impacts.A typical RF energy harvester design's main part is a rectenna module. A rectenna consists of a rectifier circuit and an antenna with filtering/matching network.Several techniques have been proposed to improve the efficiency of a rectenna system. 1 As discussed in Ref. 1, the design of a high gain and multiband antenna, and then using it as an array antenna will increase the RF energy captured wirelessly. A voltage multiplier and a multistage rectifier topology will increase the converted DC voltage. Finally, for a passive (non-bias) process, low-voltage zero biased

A wireless sensor network employing ZigBee and LoRa (Long Range) communication protocols for integration into smart building energy management systems is presented in this article. The design and implementation details are provided, and the performance parameters of the communication network are defined and analyzed based on the test results obtained from different configurations. The developed embedded system can be used in smart environments so that the room temperature, humidity, lighting systems, and so on can be automatically monitored and controlled. By customizing the embedded code, a variety of Internet of Things (IoT) applications can be introduced owing to their scalability. Taking advantage of the complementing low-power and long-range features of ZigBee and LoRa communication technologies, a system comprising an end device, a multi-protocol gateway, and a central data collector (CDC) unit is developed. The end device collects temperature and humidity as well as light intensity data using low-power sensors and sends the data to the gateway via the LoRa wireless transceiver module. The gateway was designed as an intermediate device that allows data exchange between the LoRa and ZigBee transceiver modules. It receives sensor data from the end device via LoRa and sends them to the CDC unit via a ZigBee-based XBee S2 commercial wireless transceiver module. Sensor data are monitored in the CDC unit by using an open-source IoT software platform. A commercial STM32 integrated circuit (IC) was used as a microcontroller unit for the end device and gateway. Performance parameters such as communication range and throughput data were studied for both the ZigBee and LoRa wireless transceiver modules.

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