A Dual-Band Rectifier for RF Energy Harvesting

Our cities are surrounded by a large number of radio frequency (RF) signals broadcasted by various wireless systems. In order to enhance the efficiency of energy usage in addition to the purpose of communication, ambient RF energy harvesting systems are designed to harvest and recycle wireless energy for many applications such as battery chargers, sensor devices and portable devices. The main element of the ambient RF energy harvesting system is a rectenna which is the combination of an antenna and a rectifying circuit. Even though the ambient RF energy is widely broadcasted by many systems, the energy is extremely low. Therefore, high performance antenna and rectifying circuits have to be designed for supporting small incident power; also the number of frequency channels of the rectenna can enhance the performance and support different harvesting locations. This paper proposes a dual-band rectifier for RF energy harvesting which is designed to operate at 2.1 GHz and 2.45 GHz. The first channel can provide the maximum efficiency of 24% with 1.9 V of the output voltage at 10 dBm of input power. On the other hand, a maximum efficiency of 18% and 1.7 V of the output voltage can be achieved by the second channel at 10 dBm of input power

Wireless Electric Concept and Application in a Living Room

The exploration of wireless technology nowadays has widened into a bigger area. One of the areas that is currently being researched by companies and universities around the world is supplying power to the electrical appliances wirelessly. The research is being done since the effect of the technology beneficial to both the human and sciences where power can be distributed wirelessly around the globe. This project presents an overview of a design and implementation of Wireless Electric Concept and Application in a Living Room. Research and study is carried out on how signal and energy in the air can be tapped and converted into useful energy which later can be used to supply power to electrical appliances. The approach of this work starts by harvesting Radio Frequency (RF) signal that is available in the air using RF energy harvesting circuit. This circuit collects or harvest energy in the air and converts them into electricity. It is done by using the antenna to capture the RF energy and the charge-pump circuit to convert and maguify the input signal in AC to larger output in DC. This DC output is then used to power lowvoltage equipments in the living room. Simulation work using PSPICE full edition was done to develop the concept and later was used as guidelines in developing the prototype

Design of Processing Circuitry for an RF Energy Harvester

Significant advancements in technology and the use of low power sensors in both commercial and industrial applications have made it essential to develop wireless solutions for low power devices. Once such solution, which has generated attention in university and R&D environments, is radio frequency (RF) energy harvesting. RF energy harvesting seeks to capture ambient RF energy by means of an antenna and convert this energy to useable DC power. The presence of ambient RF energy in the environment is a result of numerous high-frequency technologies including Wi-Fi, cell phones, microwave ovens, and radio broadcasting, as well as many others. The intention of this thesis is to design the processing circuitry necessary to convert a received RF signal into useable DC power, with the ability to charge a Lithium-Ion battery. The design presented here was performed to process an RF energy signal received from an antenna that targets both the 2.4GHz and 5GHz Wi-Fi bands. The final design consists of two bandpass filters (one for each Wi-FI band) two two-stage voltage doubler circuits (one for each Wi-Fi band), and a boost converter that is designed to achieve an output voltage of 3.2V in order to charge a Lithium-Ion battery. Testing of the RF energy harvester in an environment with ambient 2.4GHz Wi-Fi signals and a 470μF capacitor connected at the output demonstrates the circuit’s ability to harvest a measureable amount of energy. While the maximum measured voltage of 50mV does not meet the design specification of 3.2V, the circuit demonstrates proof-of-concept. Additional design improvements are necessary to make it a viable solution for charging a battery

A 2x4 Element Rectangular H-Slot Array Microstrip Antenna Rectifier for Harvesting Electromagnetic Energy at 2.4 GHz Frequency

This research aims to develop an energy capture system, specifically an antenna rectifier. The chosen antenna for this purpose is a microstrip antenna operating at a frequency of 2.4 GHz, utilizing a 2x4 array configuration to enhance the collection of electromagnetic waves emitted by an Access Point. To enhance the rectifier's voltage-doubling capability, the design incorporates three distinct levels: level 8, level 12, and level 14. Experimental results from implementing the 2x4 rectangular H-Slot array microstrip antenna rectifier demonstrate its capacity to convert incoming AC waves from the antenna into DC voltage. During the implementation phase, the rectenna harvesting system exhibits notable outcomes. The most significant outcome is observed in the 14th-level rectifier circuit, yielding a conversion of 101.98 mV when positioned 50 cm away from the wireless source or access point. This voltage reading diminishes to 49.148 mV at 200 cm. In the 12th-level rectifier circuit, the values are 64.8 mV at 50 cm and 39.08 mV at 200 cm. Furthermore, the 8th level circuit generates 24.72 mV at 50 cm and 11.4 mV at 200 cm. Evidently, the proximity of the testing distance correlates with the magnitude of the produced voltage

Design and development of a low-voltage DC domestic power supply system

Thesis (Master of Engineering (Electrical)) -- Central University of Technology, Free State, 2018Much effort is spent in regulating the power quality in alternating current power supplies for electronic devices. Many electronic devices, however, do not use alternating current, but rather direct current. The output of most small scale renewable energy systems are also direct current, so it can be connected to the loads more efficiently by eliminating the inverter stage. In a circuit with a number of rectification stages the conversion losses can add up to a significant amount. By reducing the number of conversion stages or possibly eliminating some of the stages the overall system could be more efficient. The purpose of this dissertation is to present the simulation design and results of a direct current distribution system, containing common household appliances connected to a direct current grid supply and a renewable energy source. A bottom-up design approach is used where a list of household appliances with their voltage needs is identified and the distribution voltage is then selected based on the voltage needs. The distribution system is modelled using Matlab and Simulink software. Results show that common household loads can be supplied directly with direct current, from either a main direct current grid supply, or a renewable energy system with direct current output. This direct current distribution system is compared to two other systems: (1) Existing alternating current system and (2) Hybrid system (converting alternating current to direct current for distribution in the house). The three systems are compared to each other in terms of power efficiency and material cost. The existing alternating current system is shown to be the most efficient, with an average power efficiency of 87.85 %. The second most efficient system is the hybrid system with average power efficiency of 86.95 %, and the least efficient of the three is the direct current distribution system with 86.45 %. The main reason why the direct current system is less efficient is because of the high input power of the microwave oven when connected to a direct current supply. The direct current system is more efficient than the alternating current system if the microwave oven load is taken out of both. Future work will involve more detailed operational and transient state simulations of the loads in the direct current system. Another recommendation is to find a direct current design for supplying the microwave oven load that does not incur large losses. A final recommendation is to build a practical test set-up of the direct current system in order to analyse the practical aspects of a residential direct current distribution system

Resonant Circuit Topology for Radio Frequency Energy Harvesting

In this work the operation of a MOSFET based rectifier, composed of multiple stages of voltage doubler circuits used for radio frequency (RF) energy harvesting, is investigated. Analytical modeling of the input stage of the rectifier consisting of short-channel diode-connected transistors is carried out, and the equivalent input resistance obtained is used along with simulation results to improve impedance matching in the harvester. The criteria for voltage boosting and impedance matching, that are essential in the operation of energy harvester under low ambient RF levels, as well as the design considerations for a pi-match network to achieve matching to 50 Ohms, are elaborated on. In addition their application is demonstrated through simulations carried out using Advanced Design System (ADS) simulator. Furthermore, measurement results of an already fabricated dual-band RF harvester are presented, and the approach taken to improve the antenna design from the harvester chip measured input impedance is discussed. The integrated antenna-harvester system tested was capable of harvesting ambient RF power and generating DC output voltage levels above 1 V