الفهرس 
Chapter 1 IntroductionOnly 14 pages are availabe for public view
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Abstract
The concept of energy harvesting is fairly old as windmills and watermills have been used from ancient times. One of the modern forms of energy harvesting is the radio frequency (RF) energy harvesting. The RF energy harvesting systems convert energy contained in RF signals available in surrounding environment into useful DC energy. Harvested DC power helps to recharge or replace small batteries in low power electrical devices and systems. Recharging batteries through RF energy harvesting has a great influence on the development of implanted devices.
RF energy harvesting system consists mainly of an antenna to collect the RF power of the wireless applications such as radio, television, mobile phones and other useful wireless instruments. Then delivers this power to RF rectifier which converts it into DC power. High operational characteristics are required for the antenna and the rectifier to efficiently harvest energy as possible.
In this thesis the performance of energy harvesting system is investigated under different operational conditions and an enhancement of the performance is proposed. The study begins by a design of a single-band rectenna to operate at 2.45 GHz. The designed rectenna is simulated, fabricated, and its performance is measured. The results show good radiation characteristics for the antenna and maximum efficiency of 32 % for the rectifier. For the purpose of increasing the harvested RF energy, a dual-band rectifier is designed. Because of the nonlinearity of the rectifying diode in addition to the intermodulation distortion results due to the operation at two different frequencies, additional frequency components appear at the output of the rectifier. These components reduce the rectifier efficiency. The effect of the intermodulation distortion is studied and as a solution to avoid its effect, the dual-input single-band rectifier is proposed. Operation of the dual-input single-band is based on feeding a dual-input rectifier with two RF signals of the same frequency. Simulation results support our suggestion and maximum efficiency of 71.7 % for the rectifier has been achieved.
Effect of operating frequency, breakdown voltage of rectifying diode, and load resistance on the efficiency of the rectifier are investigated in this work. Rectifier efficiency is better for lower operating frequencies while the breakdown voltage of the rectifying diode affects the efficiency significantly at high RF power. Efficiency of the rectifier depends significantly on the value of the load resistance. In all rectifier designs presented in this work the load resistance value is optimized for maximum efficiency.