چكيده به لاتين
Abstract
By the fast development of wireless portable electronic devices in recent years, wireless power transfer system has become one of the most interesting fields of researches; This because of that the replacement or recharge of batteries in addition to limits the operation time of such devices, is costly and sometimes impossible. Wireless power systems fall into two categories: radiative or non-radiative systems. The non-radiative systems are based on the magnetic coupling between two structures and can be classified as short-range and mid-range applications. These systems are widely developed and used in industry today. The most important issue of this method is that, it can transfer energy only over relatively low distances and frequencies used are relatively low. On the other hand, radiative wireless power transfer systems use high frequency electromagnetic waves and allow both short and long range wireless energy transfer by relatively compact devices. However, RF wireless power transfer systems are faced by basic challenges such as low efficiency and are still in research step. Access to the maximum efficiency is based on the maximum power transfer and in fact based on the impedance matching principle. The most important part of the RF wireless power systems is rectenna. Rectenna is an antenna integrated with the rectifying circuit. The efficiency of rectenna is determined by the efficiency of both the antenna and rectifier. On the other hand, the main element of rectifier is diode. Because of the nonlinear effects of diodes, input impedance of rectifier will change by variation of input power. So in this thesis, the goal is implementation of adaptive impedance matching method to compensate the efficiency decrement caused by mismatch due to the variation of input power. The rectifying circuit is designed, optimized and built. At the end, in order to receive energy from all direction an antenna structure consists of 5 microstrip antennas, is proposed and simulated.
