Design and implementation of rf energy harvesting system in cellular communication frequencies

RF energy harvesting technology is of great interest today, where the use of wireless devices and sensors has become widespread. It provides easy and free energy for applications that do not have the opportunity to provide energy from batteries. For this reason, it has become one of the most researched topics in the world. In this thesis, the design of a multiband RF energy harvesting system consisting of rectenna (antenna and rectifier circuit) and matching circuit at four different frequencies is presented. The microstrip wideband log-periodic dipole antenna is designed to harvest multiband signals including GSM (Global System for Mobile Communications), UMTS (Universal Mobile Telecommunications System) and LTE (Long-Term Evolution) frequencies. The designed antenna has good return loss performance in the range from 0.78 GHz to 3.1 GHz. The design and performance optimisation of the proposed antenna is carried out using the computer simulation software CST Studio Design. The antenna is simulated and a satisfactory peak gain of 6.3 dBi is obtained from the simulations. The antenna has been fabricated and the simulation data and VNA data are in agreement for return loss. As the next step, rectifier circuits are proposed for RF to DC conversion and high voltage output. Three-stage voltage doubler rectifier circuits using SMS7630-005LF Schottky diodes are designed to convert RF energy to DC output. T-type lumped element matching technique is used for all four bands. The design was resonant at GSM-900/1800, UMTS-2100 and LTE-2600 frequencies with the T-type bulk element matching network used for multiband rectifiers using Advanced Design System (ADS 2019) software. In addition, RF-DC maximum conversion efficiencies are 78% for 900 MHz, 79% for 1800 MHz, 75% for 2100 MHz and 65% for 2600 MHz. Rectifier output voltages are maximum 5.6 V for each frequency. Outdoor and indoor measurements of the designed RF energy harvesting system were performed. The indoor measurements for 900 MHz frequency are 3.1 V for -3 dBm input power. It is also observed that the indoor measurements are similar to the simulation results.