Aims: To give students an understanding of how electromagnetic waves propagate in typical communication engineering problems. To introduce the basic concepts behind the description of electromagnetic waves in free space, simple dielectrics and on transmission lines. To illustrate the convergence between field and circuit concepts through the understanding of simple modes of transmission on lines.
Learning Outcomes:
After completion of this unit students should be able to determine the propagation constants for waves on TEM transmission lines using circuit concepts and to illustrate the fields occurring in the simple transmission modes for parallel conductors and coaxial lines. Students should also be able to apply solutions of the EM wave equation for plane waves to propagation in dielectric and conducting media. They should be able to characterise reflections on loss-less transmission lines and for plane waves in free space at normal incidence. They should also have a qualitative understanding of reflection and diffraction effects at simple obstacles and be able to calculate the power budget for simple radiating transmission and radar systems.
Skills:
Students will learn the basic principles behind currently used techniques in transmitting radio and optical signals in transmission lines, free space and in dielectrics, and be able to establish the power budget for such transmission paths. Taught, facilitated and assessed.
Content:
Transmission lines: basic concepts; derivation of wave equation, propagation constant for loss-less lines, characteristic impedance and phase velocity from circuit concepts. Voltage, current, impedance and power flow on transmission lines; reflection and transmission, VSWR and return loss. Electromagnetic waves in free space, scalar wave equation. Propagation of plane waves, Huygens wavelets; qualitative illustration of diffraction. IEEE definition of wave polarisation. The impedance of free space. Refractive index. Propagation in dielectrics, lossy dielectrics and conductors; skin depth. Statement of boundary conditions, reflection and transmission at a boundary (normal incidence only). Antennas: antenna modelling parameters, gain and beamwidth in terms of scalar concepts (isotrope and solid angle). Derivation of the Friis formula for link power budget characterization in free space. Extension to the radar equation for point targets. Radar cross section.
|
