Abstarct: The idea of gap waveguide was introduced in 2009 by Professor Per-Simon Kildal from Chalmers University of Technology, Sweden, and it is considered a new technology compared to other branches of telecommunication science. This waveguide, especially in millimeter and submillimeter frequencies where the dimensions of the structure become very small, offers cheaper and simpler manufacturing methods than the rectangular waveguide, and has a faster production process. In addition, compared to microstrip line, the gap waveguide generally has no dielectric loss and a single structure can conduct a wide bandwidth. In this project, a leaky wave orthogonal aperture array antenna with circular polarization is designed and simulated on a ridge gap waveguide foundation. The process stages are as follows: 1) Designing the unit cell and drawing its dispersion curve 2) Design of Ku band gap waveguide 3) Designing the transition of sma into gap waveguide 4) Designing the propagating element with circular polarization 5) Designing an array of orthogonal apertures Finally, the axial ratio of the antenna designed for the frequency of 13 to 15.5 GHz is less than 3dB, and in this range, it has an average gain of 11dBi. The side-lobe level is less than -14dB and on average, it is controlled at 16.5dB and provides a gain flatness of 1.4dBi. At the initial frequency, the radiation pattern radiates towards an angle of 29° and at 15.5GHz, it is inclined towards an angle of 1°. Therefore, the designed antenna provides a 28-degree frequency scanning capability. This antenna has a radiation efficiency of 85% and a total efficiency of 77%, and compared to the cited article, it has similar results but the dimensions are half, and its production cost is also lower.