This Paper Presents Different Losses Associated With Substrate Integrated Waveguide. As Embryonic 5G Technology Use Frequency Spectrum from 28 Ghz to 100 Ghz, Which Can Be Achieved Using Mm-Wave In Which Frequency Ranging from 30 Ghz to 300 Ghz. But Limitations of This Mm-Wave Include Attenuation Due to Metal Waveguide, Atmospheric Attenuation and Rain Fade Etc. a Improved Waveguide Method Is Adapted Known As Substrate Integrated Waveguide. Siw Is Transition Between Micro-Strip Antenna and Dielectric Filled Waveguide Antenna. Siws Are Planar Structures So They Can Be Fabricated Over Pcbs and Can Be Easily Integrated With Supplementary Transmission Lines.