230 likes | 472 Views
DATA COMMUNICATION NETWORKS. MIRZA IRFAN BAIG Asst Prof Department of Information Technology Balaji Institute of Technology & Sciences Laknepally, Narsampet zissiar2@yahoo.com +91-9985287172. Electromagnetic Wave Propagation. EM Wave Plane and Spherical waves Isotropic source
E N D
DATA COMMUNICATION NETWORKS MIRZA IRFAN BAIG Asst Prof Department of Information Technology Balaji Institute of Technology & Sciences Laknepally, Narsampet zissiar2@yahoo.com +91-9985287172
Electromagnetic Wave Propagation • EM Wave • Plane and Spherical waves • Isotropic source • EM wave attenuation • Refraction and Reflection • Huygens principle • Interference • Propagation of EM Waves; sky, ground, space, duct • Free space path loss
Rays and Wavefronts: Plane wave http://www.phy.ntnu.edu.tw/java/emWave/emWave.html
Rays and Wavefronts: Spherical wave http://physics.nad.ru/Physics/English/1wa_tmp.htm
Rays and Wavefronts: Isotropic source P = power density Prad = total power radiated [W] R = radius of the sphere
EM Wave Attenuation and Absorption Attenuation is due to spherical spreading of the wave, non of the radiated power is lost Absorption is due to energy transfer from the EM-wave to the atoms and molecules of the atmosphere
Properties of Radio Waves: Refraction n1 = refractive index material 1 n2 = refractive index material 2 1= angle of incidence 2= angle of refraction
Diffraction: Huygen’s principle for a plane wave http://id.mind.net/~zona/mstm/physics/waves/propagation/huygens3.html
Diffraction: Huygen’s principle slot edge http://physics.nad.ru/Physics/English/1wd_tmp.htm http://www.rit.edu/~visualiz/projects/diffraction.html
Interference http://physics.nad.ru/Physics/English/2wa_tmp.htm
Sky wave propagation Ionosphere
Sky wave Higher RF frequencies are less refracted
Free-space path loss (spreading loss) Lp= free-space path loss D = distance (kilometers) f = frequency (hertz) = wavelength (meters) c = velocity of light in free space