الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
In short range wireless communication systems, the great need of high capacity and data rate with the lack of available frequency resources leads to shift towards higher frequencies. This rises the interest of researchers and industry to develop in mm-wave wireless communication systems. The tendency to work in such high frequencies leads to the use of smaller sized system components including waveguides and antennas, thus realizing compact size modules, at which passive, active components, antennas and waveguides are all integrated and implemented on the same chip. On the other hand, the implementation of such modules for high frequency applications is difficult especially in the presence of passive components and interconnected transmission lines with traditional technologies. The main problem is that they suffer from high losses, difficulty to integrate with other components in addition to the high accuracy required for assembly and fabrication processes to ensure good electrical contacts. To face the preceding challenges, new technology is needed. Latterly, the gap waveguide (GW) technology is introduced as a favorable candidate to address the difficulties and problems facing communication systems at higher frequencies with traditional transmission lines technologies.
The main idea of GW technology is to allow the quasi-transverse electromagnetic wave (Q-TEM) to propagate through guiding part while preventing the leakage in the other directions. Regarding the structure, the area surrounding the guiding ridge consists of two parallel layers; one is a perfect magnetic conductor (PMC) and the other is a perfect electric conductor (PEC). The gap distance between two layers should be less than quarter wavelength. There are different types of GWs that are realized based on propagation characteristics and the type of guiding path required, such as groove gap waveguide (GGW), ridge gap waveguide (RGW) and microstrip gap waveguide with different configurations; printed RGW (PRGW) and substrate integrated gap waveguide (SIGW). Mainly, the design of these gap waveguides depends on the analysis of unit cell to realize its band gap which is considered the operating bandwidth of whole structure. Firstly, we propose an approach turning the RGW design process into a simple, systematic and straightforward procedure to achieve required bandwidth and center frequency. This work is presented in order to minimize the effort and time required for the design. Nevertheless, it is important to point out that this study is mainly proposed to standardize the design procedures for this technology. Afterward, different antennas fed by RGW are designed and implemented to serve a variety of practical applications in several frequency bands. For high gain 5G applications, four-element E-plane sectoral horn array antenna fed by PRGW was designed and fabricated in millimeter wave band. Moreover, a novel four-port multiple input multiple output (MIMO) antenna based on SIGW with superior diversity performance was proposed and fabricated for satellite xi
down link applications. A PRGW based bow-tie slot antenna loaded with three dielectric superstrate layers is proposed to enhance both the antenna gain and bandwidth for 5G and 6G applications.