34615 - Propagation and Electromagnetic Interference M

Learning outcomes

The goal of the course is to deepen the knowledge of electromagnetic phenomena and to explain the principles of wave propagation both in free space and guided, and of electromagnetic interference (EMI). Shielding techniques for EMI problems.

Course contents

Time-variable electromagnetic fields

Inhomogeneous wave equations. Retarded potentials

Quasistatic electromagnetic fields

Quasistatic description of electromagnetics. From fields to circuits. Generalized integral form Ohm's law. Diffusion phenomenon. Skin effect for a cylindrical conductor in sinusoidal steady state.

Waves in an unbounded medium

Time-domain wave equations in a source-free medium. Uniform plane waves (TEM waves) in a lossless medium. Uniform plane waves in lossy media: general case. Re-examination of the conductor and insulator definition. Uniform plane waves in conductors and lossy dielectrics. Dispersive materials. Electrical dimensions. Study of an electrical small structure through the diffusion equation in terms of the magnetic vector potential and application to mutilayered shields. Analogy between uniform plane waves and transmission lines. Normal incidence of waves at planar interfaces. Shields. Shielding effectiveness. Methods and techniques for the calculation and measurement of the shielding effectiveness. 

Rectangular waveguides

Solution of wave equations in a rectangular waveguide filled with a source-free and lossless material. Transverse magnetic (TM) modes. Transverse electric (TE) modes. Wave propagation in the guide.

Elemental dipole antennas

Electromagnetic field radiated from elemental dipoles. Electric dipole (hertzian dipole) and  magnetic dipole (small loop). Near and far field approximations. Impedance of the near field. High and low impedance fields.  Average power radiated by the elemental dipoles. Radiation resistance.

Method of images

Theory. Application to the calculation of the per-unit-length equivalent capacitance of a two-conductor transmission line above the ground plane.

Readings/Bibliography

- F. Barozzi, F. Gasparini, Fondamenti di elettrotecnica: elettromagnetismo. UTET, Torino, 1989.

- S. M. Wentworth, Fundamentals of Electromagnetics with Engineering Applications. Wiley International Edition, 2005.

- M. N. O. Sadiku, Elements of Electromagnetics, 4th ed. Oxford University Press, New York - Oxford, 2007.

Teaching methods

Lectures. Numerous example problems are worked-out for reinforcement of the course material.

Assessment methods

The final test has the aim of verifying the achievement of the following learning objectives:

• knowledge of physical concepts and tools of analysis provided in the lectures,
• ability to use these tools to analyse phenomena of electromagnetic wave propagation, electromagnetic interferences (EMI) and electromagnetic shielding methods and techniques,
• ability to employ the results obtained to interpret the phenomena of electromagnetic interference under study and to identify measures to mitigate them.

The test is oral and usually consists of three questions on three different topics of the program (theory and exercises).

Office hours

See the website of Ugo Reggiani