This paper presents a new family of spreading code sequences called hybrid prime code (HPC), to be used as source code for the optical code division multiple access (OCDMA) network for large network capacity. The network capacity directly depends on the number of available code sequences provided and their correlation properties. Therefore, the proposed HPC is designed based on combining two or more different code words belonging to two or more different prime numbers. This increases the number of code sequences generated. The code construction method utilized allows the generation of different code sets, each with different code length and weight, according to the number of prime numbers used. In addition, the incoherent pulse position modulation (PPM) OCDMA system is proposed based on the HPC code. Furthermore, the bit error rate (BER) performance analysis is introduced versus the received optical power and the number of active users. Moreover, the error vector magnitude (EVM) is calculated versus the optical signal-to-noise ratio. This work proves that using two prime numbers simultaneously generates far more codes than using prime numbers separately. It also achieved an OCDMA system capacity higher than the system that uses the optical orthogonal codes (OOCs), modified prime codes (MPCs) families, and two code families with separate simultaneously prime numbers, at a BER below 10−9 which is the optimum level.
In this paper, a nano solar cell structure based on a two-dimensional photonic crystal (2D-PhC) antireflection coating (ARC) trapping layer and a 2D-graded-index (2D-GI) GaAs active layer is presented. These components improve the solar absorption, in-coupling efficiency, quantum efficiency, and optical properties of the active layer. The proposed cell absorption and conversion efficiency were analyzed as a function of the cell layer thickness in comparison with the Lambertian absorption and cell efficiency limits. Additionally, each layer thickness was optimized to enhance the overall solar efficiency. All simulations were conducted in the 300 to 1100 nm range using finite difference time domain (FDTD) analysis, where the 2D-PhC structure was represented by indium tin oxide (ITO) nanorods in an air background. In addition, p-Al(0.85)GaAs/n-Al(0.35)GaAs two-window confinement layers are utilized in contact with the 907-nm GaAs active layer as a perfect match with the 1840-nm ITO-ARC layer to improve the confinement efficiency. Moreover, p-Al(0.85)GaAs/GaAs and GaAs/n-Al(0.35)GaAs 2D-GI active layer structures are used for index modulation to enhance the active layer properties and increase the cell short-circuit current. The main objective of this study is to determine the optimum design of a solar cell that can provide the highest power conversion efficiency using inexpensive semiconductor materials. One of the expected results from this research is the design of a 100-µm 2 nano solar cell with 39.2% conversion efficiency, a short circuit current density of 44.38 mA/cm 2 , and an open-circuit voltage of 1 V.
INDEX TERMSTwo-dimensional photonic crystal (2D-PhC), light trapping, 2D-index modulation, absorption, conversion efficiency, short circuit current, open circuit voltage.
This paper presents a Sunlight-Radio Frequency (RF) energy harvesting system built on Solar Panel Mesh Dipole Antenna integration. The dipole antenna mesh is mounted on the surface of the solar panel at the separations between the cells. This configuration maximizes the absorption of both solar and RF energies. Further, the multiple mesh antennas are integrated vertically to increase the RF harvested power. Each antenna output is connected to a six-stage RF-Voltage Doubler Rectifier (RF-VDR) circuit to convert the RF signal to a direct current (DC) and added to the solar panel DC output. This paper involves the design analysis of the antenna parameters, the integration process, and the design of the RF matching circuit. Prototype tests show that the proposed mesh dipole antenna has 83% efficiency. This is better than earlier similar designs published. From previous designs, the measured RF to DC conversion efficiency (CE) of the VDR circuit was merely 62% when the RF input equals -14 dBm. Moreover, the solar panel efficiency has been enhanced by 41.3 % when the input RF power density equals 49.16 mW/m 2 . Finally, the results proved that the proposed solar antenna system achieves 28.5 % power CE and outperforms the others that use transparent patch antennas.
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