A two-port MIMO Dielectric Resonator Antenna (DRA) has been proposed and studied. The antenna consists of a single Rectangular DRA (RDRA) element housed in a thin FR4 substrate, that is fed by two microstrip feed lines. Both the feeding lines excite (Formula presented.) mode in the RDRA. The mutual coupling between the ports has been decreased by employing two symmetrical slits in the ground plane. The proposed antenna has been fabricated and a parametric study has been carried out to obtain the optimum parameters. The presented antenna with acceptable MIMO characteristics, covers a measured bandwidth of 80 MHz (2.56–2.64 GHz) for |S11| < −10 dB, which is able to operate on LTE band 38. The measured isolation between the two ports for the desired frequency band is better than 20 dB. The presented antenna has been examined by calculating and measuring the Envelope Correlation Coefficient, Mean Effective Gains and the Diversity Gain. Based on the study that has been carried out, the antenna offers easy fabrication, feeding and good MIMO characteristics. Therefore, the presented antenna can be a suitable candidate for LTE applications
Daylighting has a very effective role in reducing power consumption and improving indoor environments in office buildings. Previously, it was not under consideration as a major source of renewable energy due to poor reliability in the design. Optical fiber as a transmission medium in the daylighting system demands uniform distribution of light to solve cost, heat, and efficiency issues. Therefore, this study focuses on the uniform distribution of sunlight through the fiber bundle and to the interior of the building. To this end, two efficient approaches for the fiber-based daylighting system are presented. The first approach consists of a parabolic mirror, and the second approach contains a Fresnel lens. Sunlight is captured, guided, and distributed through the concentrator, optical fibers, and lenses, respectively. At the capturing stage, uniform illumination solves the heat problem, which has critical importance in making the system cost-effective by introducing plastic optical fibers. The efficiency of the system is increased by collimated light, which helps to insert maximum light into the optical fibers. Furthermore, we find that the hybrid system of combining sunlight and light emitting diode light gives better illumination levels than that of traditional lighting systems. Simulation and experimental results have shown that the efficiency of the system is better than previous fiber-based daylighting systems.
Fiber-optic daylighting systems have been shown to be a promising and effective way to transmit sunlight in the interior space whilst reducing electric lighting energy consumption. To increase efficiency in terms of providing uniform illumination in the interior, the current need is to illuminate optical fiber-bundle with uniform light flux. To this end, we propose a method for achieving collimated light, which illuminates the fiber-bundle uniformly. Light is collected through a parabolic concentrator and focused toward a collimating lens, which distributes the light over each optical fiber. An optics diffusing structure is utilized at the end side of the fiber bundle to spread light in the interior. The results clearly reveal that the efficiency in terms of uniform illumination, which also reduces the heat problem for optical fibers, is improved. Furthermore, a comparison study is conducted between current and previous approaches. As a result, the proposed daylighting system turns out convenient in terms of energy saving and reduction in greenhouse gas emissions.
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