Recent years have illustrated the significantly pervasive interest in transparent antennas. The number and the popularity of transparent antenna applications have escalated dramatically. Although antenna applications are diverse and available across multiple platforms, some of these antennas are unsuitable for practical usage, particularly in cases associated with renewable energy. As such, this study presents the review of related articles pertaining to transparent antennas across a range of platforms to identify their best practices. The methods applied in prior research work within this domain were identified. Relevant articles published between 2015 and September 2020 were gathered from four major databases: Science Direct, Web of Science (WOS), IEEE Xplore, and Scopus. The identified indicators were considered as broad and reliable to cover this field of literature. The articles (n=81) were selected based on inclusion and exclusion criteria. This paper concentrates on the present views and opportunities to further understand the research segment of transparent antenna.

Ultraviolet photodetectors have been widely utilized in several applications, such as advanced communication, ozone sensing, air purification, flame detection, etc. Gallium nitride and its compound semiconductors have been promising candidates in photodetection applications. Unlike polar gallium nitride-based optoelectronics, non-polar gallium nitride-based optoelectronics have gained huge attention due to the piezoelectric and spontaneous polarization effect–induced quantum confined-stark effect being eliminated. In turn, non-polar gallium nitride-based photodetectors portray higher efficiency and faster response compared to the polar growth direction. To date, however, a systematic literature review of non-polar gallium nitride-based photodetectors has yet to be demonstrated. Hence, the objective of this systematic literature review is to critically analyze the data related to non-polar gallium nitride-based photodetectors. Based on the pool of literature, three categories are introduced, namely, growth and fabrication, electrical properties, and structural, morphological, and optical properties. In addition, bibliometric analysis, a precise open-source tool, was used to conduct a comprehensive science mapping analysis of non-polar gallium nitride-based photodetectors. Finally, challenges, motivations, and future opportunities of non-polar gallium nitride-based photodetectors are presented. The future opportunities of non-polar GaN-based photodetectors in terms of growth conditions, fabrication, and characterization are also presented. This systematic literature review can provide initial reading material for researchers and industries working on non-polar gallium nitride-based photodetectors.

Minimal profile antennas for wireless devices which characteristics consisted of being low cost, highly reliable, and lightweight, it bears a new challenge for the design of the antenna in wireless communications. In this paper, we propose a design of circularly polarized microstrip patch antenna integration with solar cells for green wireless applications. Two techniques have been proposed to form the prototype between the communication system (design of antenna) and solar panel (solar cell). Both methods will face two issues generally; the solar system needs to get 100% sunlight and the magnetic field produced by radio communication systems as well as the electric field produced by solar cells should not affect the efficiency. The antenna is composed of a Koch fractal loop patch and the substrate is employed using a transparent material. This enables the light to pass through with high efficiency to illuminate the solar panel cells while the RF performance is maintained with minimal degradation. The communication frequency measures 2.6, 3.5 and 4.4 GHz. CST MWS simulation is also studied and compared among the different substrates which show different results based on the same parameters, which is implemented with a lattice of 2×2 square solar cells. With this arrangement, the solar cells will be able to obtain 100% of sunlight exposure. The characteristics of the broadband are achieved by combining resonances and the minimum axial ratio points created by the driven patch and solar cell surface.