Abstarct: In recent years, wireless communications have become a rapidly growing phenomenon in the communication industry. The rapid growth of wireless communication has increased the demand for integrated and very compact structures with improved antenna properties. Many microwave antennas are designed using micro-strip circuits with proper features such as low cost, smaller size, and easy to integrate. But when these micro-strip circuits operate at higher frequencies, the radiation losses are high. In order to prevent such a situation, waveguide circuits are used. These circuits show minimum radiation losses but also have their own disadvantages. Compared with micro-strip circuits, they do not integrate easily. Therefore, a new kind of technology has been introduced called integrated waveguide substrate which has the benefits of both waveguide and micro-strip circuit. It has the benefits of micro-strip circuit such as compact size and easy integration and the benefits of waveguide circuit such as low radiation losses. The siw implements a waveguide on a printed circuit board using two rows of mextal cylinders called Via. In this thesis, a new SIW antenna with widespread semi-isolated walls have been studied and analyzed. In stead of introducing extra loading on the elongated substrate and / or constructing multi-laxyer structures, we can significantly expand the SIW antenna impedance bandwidth through the separation of widespread mextal walls in antenna’s opening. In addition, optimization of antenna parameters has been done which can be desirable in in guiding the designing of different antenna stages. SIW antenna has been constructed and the measured results of reflection coefficient, increase, efficiency, and radiation pattern have been shown in chapter The proposed antenna is designed and simulated using CST software. It can be seen that the simulated vswr is less than two frequencies from 7GHz to 13GHz for the vswr standard. The measured S11 with the standard of S11 less than -10dB from 7GHz to 13GHz has been obtained. In previous designs, it has been shown that it has a very narrow bandwidth, however their height is slightly smaller than our design. Compared with many typical SIW horn antennas, our proposed SIW antenna is more complicated structurally with broader bandwidth and better directionality.