چكيده به لاتين
Vivaldi antenna is one of the most important components in satellite communications, radar and photography. Due to the fact that these antennas have a printed circuit structure, they are not complicated to implement and build and do not have a high manufacturing cost. The main feature of these antennas is their high bandwidth and easy matching of their impedance with the microstrip input feed line. In recent years, a lot of research has been done to improve the antenna power and output characteristics of the antenna, including the radiation pattern and antenna gain and return losses and increase its bandwidth. In this dissertation, in the first chapter, we first present a history of the invention of this antenna, and in the second chapter, to explain the physical characteristics of the Vivaldi antenna structure, and then, the various methods of feeding the antenna and examining different geometric curves. We examine the work done in the radiation part of the antenna. In the third chapter, we describe the radiation mechanism and the limitation of the optimal performance of the antenna with increasing frequency, and we examine the main methods used to improve the antenna gain and improve its radiation pattern in more bandwidth. The methods include creating consecutive gaps in the antenna radiation curve, using metamaterial structures and , adding parasitic elements. Then we introduce the implementation method of Vivaldi anti-pedal antenna, which is based on the Fourier series. In Chapter 4, with the help of a Vivaldi anti-pedal antenna in the X-band, we begin the initial design of the antenna by equating two curves with the non-uniform method, and these two curves with the initial coefficients of the Fourier series, which is equivalent to the initial curve of the antenna. Is the base, we approximate. We then optimize the two-curve coefficients enough to achieve the best possible bandwidth with low return losses and a suitable radiation pattern. Then we change the antenna substrate and by observing the results and comparing it with the previous case, this time we increase the number of Fourier series coefficients of the two designed curves. To improve the output results of the antenna at higher bandwidth, we constantly increase the number of coefficients until the optimization of the coefficients no longer significantly changes the results.
