چكيده به لاتين
Today, high-gain antenna technology, in addition to long-distance telecommunication applications, has been rapidly developed with the increasing demand for high speed and wide channel capacity in modern mobile communication systems, especially in the working frequencies of the fifth generation of mobile communication. Waveguide antennas, microstrip antenna arrays, and 3D lens antennas are some of the most common high-gain antennas. Waveguide-based antennas are bulky and not suitable for miniaturization and integration. Microstrip antenna offerings are high-gain antennas ideal for miniaturization and integration, but they suffer from severe dielectric loss as the operating frequency increases and are also not suitable for high-power applications. In addition, most of the 3D dielectric spherical lens antennas have a large volume and it is difficult to achieve system-level integration. Recently, researchers have found a simple and easy way to have an efficient 2D planar high gain antenna based on phase gradient hypersurfaces. These antennas have attracted a lot of attention due to their advantages such as high gain, simplicity and low cost. These antennas are composed of two parts including feed and supersurface. Feeding a microstrip antenna with a gain of about 6-7 dB. The most important part in the design of metasurfaces for various applications is the design of the unit cell. After the effective design of the unit cell, it can be used in different applications, including the design of the lens antenna. Traditional and conventional designs of unit cells, which are based on step-by-step changes (sweeping) of design variables or using optimization techniques, have disadvantages such as time-consuming and in some cases computational complexity. In addition, with the change of demand, for example transmissive or reflective surface or change of working frequency, the design must be redone, which is a long and inefficient process. In this research, we are looking to use new methods of cell design of ultra-surface units with the aim of responding to the needs of today's telecommunication world. Recently, the use of artificial intelligence platform has been suggested by researchers as a suitable solution when the design based on common optimization methods becomes complicated. Therefore, the basis of the work in this process is the use of automatic design of the unit cell and the use of artificial intelligence platform for various applications of ultra-surfaces in two transmission and reflection modes at different frequencies (from 12 to 18 GHz). In this regard, in this thesis, the method of automatic design of unit cell using machine learning technique of a multi-bit multi-functional hypersurface with the ability to work in several working frequencies is presented. After designing the metasurface, several high gain antennas are designed and simulated based on the phase gradient metasurface in transmission and reflection modes at different frequencies. At the end, a sample of simulated high gain lens antennas at 14 GHz has been built and its parameters have been measured.
