RF ENERGY HARVESTER
FOR SELF-SUSTAINABLE APPLICATIONS
Project Overview
In recent years, the applications of self-sustainable electronics devices are increasing rapidly in the sectors of IoT, implantable biomedical devices, and wireless sensors networks (WSN). Due to finite battery life and widespread availability of RF electromagnetic energy, improvement of existing RF EH becomes a promising topic to the researchers. The RF Energy Harvester is a unique proposal with higher RF-to-DC conversion efficiency compared to previous publications.
The Objective of this project is to develop an RF energy harvester with high RF-to-DC conversion efficiency and to explore the viable path towards implementing in Integrated Circuit (IC) from using silicon process technology.
Cadence Simulation and Results
Input Waveform (1MHz)
Output Waveform (1MHz)
Input Waveform (900MHz)
Output Waveform (900MHz)
Design
Optimization
Iterative simulations were done to select the optimum number of stages to attain the maximum voltage with the highest conversion efficiency. We tested the system on a smaller scale with an input power of 0dBm at 1MHz frequency.
The output signal is measured across a 100kΩ resistor and the RF-toDC efficiency (ƞ) is calculated as the ratio of output DC power and input AC power.
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Similarly, Iterative simulations were done to select the optimum number of stages to attain the maximum output voltage with the highest conversion efficiency for the 900MHz frequency signal. As shown in figures to the left, we obtained the maximum output voltage with the highest conversion efficiency listed below.
Project Prototypes
1MHz Prototype
The RF EH was tested on a lower frequency of 1MHz to insure the proper working order of the system and so that it would be feasible to prototype on a breadboard with the available components. Test Results are shown below.
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900MHz Prototype
The final product was implemented on a 2 layer PCB designed on EAGLE. Iterative measurements were done to obtain maximum efficiency. 330
µW of 900MHz RF input converts into 1.48V DC, which lights up an SMD LED consuming about 22µW. This is equivalent to lighting up the same LED wirelessly with a power of 1mW and using transmit/receive antennas each having 5dBi gain over a distance of half a meter.
Challenges
During the design and testing process of this project, we faced multiple challenges. Some major challenges are listed below.
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There was a discrepancy between the simulation and measured results due to the model mismatches of the circuit components
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Optimized values of the components had tolerance due to their availability in the market
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Parasitic extractions of the PCB Layout