28719 - Electromagnetic Fields T-1

Learning outcomes

Understanding of phenomena concerning free and guided propagation  of electromagnetic fields and their use in telecommunication systems. Knowledge of transmission lines and of the most used waveguides. Ability to solve matching problems.

Course contents

Theoretical models to study electromagnetic fields

·          Vector theory

Basic principles. Material constitutive relations.
Poynting and Uniqueness Theorems (in the time domain).
Field polarization. Time harmonic fields and complex vector quantities.
Harmonic regime fields. Poynting, Uniqueness, Equivalence and Reciprocity Theorems.
Discontinuities and surface currents. Perfect electric and magnetic conductors. Duality principle.

·          Scalar theory

·          Geometical theory

Ray equation.
Optical path.
Limits in geometrical optics: Fresnel ellipsoid.

Maxwell's equation solution

·          Without sources

Helmholtz equation.
Solution of the Helmholtz equation in homogeneous media: Plane waves and their classification.
Effect of discontinuities. Reflection and refraction. Total reflection and refraction.
Stratified media.
Plane wave beams propagation. Parabolic approximation.

·          With sources.

Scalar and vector potentials.
Green function method.

Free propagation

·          Antennas

General features of antennas.
Elemental current. Field radiated by an elemental current. Near and far field approximations.
Antenna equivalent moment.
Fundamental parameters of an antenna: radiation intensity, radiation function, directivity and gain. Effective area.
Composite antennas and arrays
Friis formula.
RADAR equation.

Guided propagation

·          Transmission lines

Basic equations
Low loss transmission lines.
Propagation and attuenuation constants.
Loaded lossless transmission lines: Voltage Standing Wave Ratio.
Smith chart
Source and load mattching:
Impedance matching with lumped elements.
Impedance matching with distributed elements: single stub, double stub, quarter wavelength, principles of multisection transmission lines.

·          Waveguides

Coaxial cable.
Rectangular waveguide.
Circular waveguide.
Introduction to optical fibers.

Readings/Bibliography

Libro di testo : Paolo Bassi, Lara Scolari, Rossella Zoli, "Propagazione di onde elettromagnetiche", CLUEB 2009, http://www.clueb.com/servlet/SchedaArticolo?cat_id=3155

Further reading : websites   http://elearning.ing.unibo.it   and http://pbassi.deis.unibo.it/Avvisi_agli_studenti.htm (in italian, access restricted to students of the course)

Teaching methods

During lecture hours, the general pinciples of free or guided propagation of electromagnetic fields in view of signal transmission are illustrated. 

Practice hours (in the classroom or in the laboratory, taking advantage of dedicated software) illustrate examples of application of the theoretical ideas illustrated during lectures, showing how they are useful in practice to solve real problems.

At the end of the course, students will know the general principles of electromagnetic theory, the main features of the different models developed to study electromagnetic propagation and the relevant limits. They will then be both able to critically evaluate the most suitable model to apply and the precision of the results it may provide and to apply them to solve problems of technical interest.

Assessment methods

The exam consists in a written and an oral part.

The written part may be split in two parts (the former during the course, the latter after its end) or a single one (after the end of the course).

Once the written part is passed, the oral part takes place and concludes the exam.

The written parts aims to check that the student can apply the studied theory solving some exercises.
The oral part aims to check the knowledge and the understanding of the general principles of the studied theory and his ability of discuss them with propriety of language.

Teaching tools

Perconal Computer with dedicated software.

Office hours

See the website of Paolo Bassi

See the website of Giovanni Tartarini