A metasurface is a two dimensional periodic structure which possesses macroscopic equivalent electromagnetic properties such as anisotropy, negative refractive index and Electromagnetic Band Gaps (EBG). EBGs have been used for the design of waveguide filters and gap waveguides. In this thesis, a transition between stripline and waveguide technology is designed for the standard 5G frequency band of 28 GHz. In addition, a metasurface will be designed and placed in the surroundings of this transition with the objective of suppressing the leakage that appears in the air gap between the Printed Circuit Board (PCB) and the waveguide flange. The transition is embedded in the PCB technology while the metasurface is built in two different technologies at each layer: PCB and holey metal. There are non existing studies of this hybrid composition of a metasurface, therefore, a thorough study of this structure has been carried. The proposed technology simplifies the connection between elements, avoiding the leakage due to imperfect connection between layers. Commercial software CST Microwave Studio Suite is used for simulations. A prototype has been built and measurements have been carried out in order to compare the simulation results with a real manufactured design.