In this paper, we present a study of ambient RF energy harvesting techniques. The measurement of the ambient RF power density is presented. The average of the density in broadband (1GHz-3.5GHz) is in the order of-12dBm/m² (63µW/m²). Two systems have been studied to recover the RF energy. The first is a broadband system without matching circuit. The second is a narrow band system (1.8-1.9GHz) with a matching circuit. The rectifier circuit RF / DC and the choice of the load to optimize the DC power recovered are presented. The preliminary results indicate that the recovered energy is not sufficient to directly power devices but could be stored in a super-capacity or micro-batteries.
In the present work, photovoltaic solar cells are used in patch antenna structures. The radiating patch element of a patch antenna was replaced by a solar cell. Direct Current (DC) generation remained the original feature of the solar cell, but additionally it was now able to receive and transmit electromagnetic waves. Here, we used a new patch antenna structure based on a photovoltaic solar cell. It was then used to collect photo-generated current as well as Radio Frequency (RF) transmission. A mathematical model which would serve the minimization of power losses of the cell and therefore the improvement in the conversion efficiency was studied. A simulation allowed analyzing the performance of the antenna, with a silicon material, and testing its parameters such as the reflection coefficient (S11), gain, directivity and radiated power. The performance analysis of the solar cell patch antenna was conducted using Advanced Design System (ADS) software. Simulation results for this antenna showed a dual resonance frequency of 5.77 GHz and of 6.18 GHz with an effective return loss of -38.22dB and a gain of 1.59dBi.
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