Architecture of Ultra Low Power Micro Energy Harvester Using RF Signal for Health Care Monitoring System: A Review

Abstract

This research presents architecture of Ultra Low Power (ULP) Micro Energy Harvester (MEH) using Radio Frequency (RF) signal as an input. RF has many advantages compared to other ambient sources because it is not affected by changes of weather or time, does not require heat or wind exposure and it can be moved randomly within the bound of the transmission source. When RF is used as the sole input, the designer needs to consider impedance matching as the most important element so that the antenna can transfer maximum power. The existing energy harvesters apply conjugate matching network as the current solution. However, this method causes some difficulties since the solution requires consideration of both voltage boosting and conjugate matching network simultaneously. To solve this problem, we propose ULP Radio Frequency Micro Energy Harvester (RFMEH) that will utilize a control loop as voltage boosting adjuster and network tuner to achieve maximum power transfer and minimum power reflection. The proposed architecture will also improve the RF-DC conversion efficiency and the sensitivity of the system. This is achieved using an efficient rectification scheme to convert RF to DC, DC-DC boost converter to increase the dc output voltage, adaptive control circuit to adjust the switching timing of boost converter, voltage limiter and regulator to produce the best output voltage. The proposed ULP RFMEH architecture will be designed and simulated using PSPICE software, Verilog coding using Mentor Graphics and functional verification using FPGA board (FPGA) before being implemented in CMOS 0.13 µm process technology. The proposed architecture will deliver approximately 2.45 V of output voltage from low input power level (-20 dBm) with an efficiency of more than 60%. This design will minimize the power consumption as compared to previous achievements and it can be applied in supplying power for health care monitoring systems or micro biomedical applications.