High Gain Antenna Array Design for 5G & MIMO Antenna Systems using Microstrip Ridge Gap Waveguide

The demand for high data rates and the unavailability of low-frequency bands have driven the need to explore and develop millimeter-wave (mm-wave) frequency bands. Indeed, the development of mm-wave frequencies has led to smaller radio frequency (RF) components and more compact profiles, creating more design constraints and challenges. Millimeter-wave technologies are the best-suited candidates that meet the requirements of 5G standards; specifically, for indoor communication, which requires higher gain and more directive beams. Gap waveguide technologies can be used to design high-gain antenna arrays and multiple input multiple output antenna systems (MIMO). In this thesis, we are mainly focusing on Microstrip Ridge Gap Waveguide (MRGW) to design the antenna array systems for the 60 GHz band. Therefore, it is necessary to facilitate the design procedures and propose new design techniques. Here, we propose new design techniques for a large antenna array system using MRGW. The work of this thesis can be divided into two parts. Firstly, developing an efficient modeling and design tool for the MRGW to facilitate the design process. Recently, the use of MRGW has increased due to the need for self-packaged and low loss structures for millimeter-wave applications. The MRGW consists of a grounded textured surface, which is representing an artificial magnetic conductor (AMC) surface. The AMC surface is loaded with a thin low dielectric constant substrate with a printed strip topped with another air-filled or dielectric-filled substrate in which the wave propagates between the strip and the conducting plate covering such a substrate. Currently, full-wave and optimization tools are usually used to design the MRGW structure, which makes the design slow and computationally expensive. Thus, an efficient modeling and design tool for the MRGW is proposed. Empirical expressions are developed for different MRGW parameters to provide the effective dielectric constant, characteristic impedance, and the dispersion effect. The expressions are verified with the full-wave solution. The results show the potential of the proposed approach in modeling and designing the MRGW structure. Secondly, an efficient procedure to design a large finite planar array and its corporate feeding network is presented. The procedure is verified by an 8 × 8 and 16 ×16 array of magneto-electric (ME) dipoles fed by a network of MRGW. The procedure is based on designing the corporate feeding network by replacing the elements ports with the corresponding effective input impedance of each element that accounts for the mutual coupling between the antenna elements. In addition, the far-field characteristics of the array parameters such as the directivity, gain, and radiation patterns are predicted using pattern multiplication, including the mutual coupling effects. The results are verified with the full-wave numerical solution. The procedure requires limited resources and speed up the design cycle. The use of the MRGW helps in having the feeding network lines to be titer than using the ridge gap technology. Thus, allowing the distance between the radiating elements becomes smaller than one wavelength to avoid grating lobes. In addition, to avoid undesired bends and very tight lines that cause undesired interaction between the lines, unique power dividers are designed. Furthermore, a transition from waveguide WR-15 to the MRGW is proposed to feed two halves of the array antenna perfect out of phase at all frequencies and rotating each half to form a mirrored array that better radiation pattern symmetry and low cross-polarization. Then, this procedure is implemented to design a circularly polarized antenna array with excellent performance. To further enhance the antenna, gain, and reduce the number of elements, a superstrate dielectric lens with the proper parameters is added. Study of a 4 × 4 MIMO system is studied, where each antenna is a sub-array to achieve the high gain requirements. Finally, A low-profile, compact, and high-efficiency monopulse array antenna has been presented. The monopulse is built based on a hybrid coupler that has a wideband response for the reflection and the transmission coefficients. Then the monopulse system is used to present a multiplexing antenna system for short-range in the near filed region wireless communication. The multiplexing system works as a MIMO system that has four independent channels. The performance of the system is evaluated through the simulation, which shows that it can be a promising candidate for the next wireless communication systems

Iron, Copper And Tin Incorporated Rice Husk Ash Silica: Preparation, Characterization And Application As Catalysts For Friedel-Crafts Benzoylation Reactions

Iron, copper and tin incorporated silica catalysts were prepared via sol-gel method using the silica extracted from rice husk ash. The modified catalysts were denoted as RHA-xFe (x = 5, 10, 15 and 20 wt.%), RHA-10Cu and RHA-10Sn. Prepared catalysts were characterized by various physico-chemical techniques such as XRD, FT-IR, N2-sorption, AAS, SEM-EDX, TEM, DR UV/Vis, solid state 29Si MAS NMR, EPR, TGA-FT-IR and FT-IR-pyridine adsorption. The catalysts were found to be amorphous. Elemental analysis confirmed the presence of the metals in the silica framework

Hepatic and gastrointestinal complications after adult cardiac surgery

Background: Gastrointestinal tract (GIT) complications are associated with increased morbidity and mortality after cardiac surgery. Therefore, The goal of this research was to estimate the frequency of GIT and hepatic complications after cardiac surgery and to determine the risk factors for these complications. Additionally, we studied the effect of these complications on the outcomes of surgery. Methods: This longitudinal study included 139 consecutive patients who underwent elective cardiac surgery. Patients were grouped according to the GIT and hepatic complications into two groups. Postoperative outcomes were compared between the two groups.   Results The mean age was 59.43 years, and 106 patients were males (76%). The GIT and hepatic complications rate was 15.8% (n= 22). Hepatic dysfunction occurred in 8.6% of cases, GIT bleeding in 2.9%, paralytic ileus in 2.2%, fulminant hepatic failure in 2.2%, and GIT bleeding combined with paralytic ileus in 0.7%. The overall mortality was 7.2 % (n= 10). The mortality rate in patients who developed GIT and hepatic complications was 45.5% (n= 10 out of 22 patients). There was statistically significantly higher mortality (10 (45.5%) vs. 0; P= 0.001), cardiac arrest (10 (45.5%) vs. 3 (2.6%); P= 0.001), and reoperation rate (5 (22.7%) vs. 6 (5.1%); P= 0.005) among patients with GIT or hepatic complications. Conclusion: Patients with hepatic and GIT complications could have higher mortality, morbidity, and longer hospital stay than the non-complicated group