Recently, there has been an increased interest in high data rate (millimeter wave frequencies) systems, towards 5G network. Millimeter wave systems have an advantage of wide bandwidth, higher resolution, cost efficiency and smaller component sizes. Substrate integrated waveguide (SIW) is a good candidate for millimeter-wave systems, offering low loss, high quality factor and lower cost. This thesis presents a brief introduction to the conventional waveguide, planar transmission lines, the main characteristics of the substrate integrated waveguide antenna (SIW) including losses, bandwidth and design rules for SIW. The novelty of the slotted substrate integrated waveguide (SSIW), that allowed the integration of lumped elements along the slot, is presented in chapter 2. The slotted SIW supports half mode TE1/2,0. A novel antenna in SSIW is designed using CST (microwave studio) and fabricated. Additionally, the various parameters of the SSIW antenna have been studied, as well as their effect on resonant frequency and matching. To enhance gain, a 2 × 2 SSIW array has been simulated and shown to improve the gain by 6 dBi. A novel tri-band antenna is presented in chapter 3. The final design is a tri-band substrate integrated waveguide antenna. This design could Possibly tune the resonant frequencies with additional slots to the antenna. The design has open-end terminations and acts as a dual waveguide region based on half mode TE½,₀ of each region. Different modes and their resonant frequencies were studied, as well as parameters' effects on tri-band SIW antenna. To increase gain and reduce side lobe level, a 2 × 2 array has been simulated and fabricated. The possibility of tuning the response of SIW waveguides using graphene is studied in Chapter 4. This was done by applying an electric field to the graphene to modulate its conductivity. The difficulties associated with this are studied and some solutions are suggested to tuning the waveguide. Chapter 4 also presents measurements of the conductivity of mono-, bi- and tri-layers of graphene at millimeter-wave frequencies and suggests a waveguide calibration scheme for the network analyzer measurements based on the layers of graphene.