17938 - Electromagnetic Fields Propagation (L-A)

Learning outcomes

Development of a thorough scientific-methodological understanding of the basic principles of electromagnetic field propagation, both free and guided. Knowledge of radiation phenomena in the free space and of reception of radio signals. Knowledge of the principal wave-guiding structures and of their use both in telecommunication systems and in high-frequency integrated circuits. Ability to make a first-approach evaluation of a radio as well as of a cable link.

Course contents

Basic postulates of the electromagnetic field. Field sources and receivers. Maxwell's equations in the time domain and material constitutive relationships. Divergence equations. Wave equations. Poynting's and uniqueness theorems in the time domain.

Sinusoidal electromagnetic fields. Sinusoidal vector quantities and their representation by complex vectors. Polarisation. Complex electromagnetic field. Maxwell's equations in the frequency domain. Helmoltz's equations.

Continuity equations for the field through a discontinuity surface of the constitutive parameters. Surface and linear currents. Perfect electric conductor. Duality theorem and its applications: perfect magnetic conductor.

Basic theorems in the frequency domain. Poynting's theorem. Uniqueness theorem. Resonant cavities. Equivalence theorem. Thévenin and Norton theorems. Reciprocity theorem. Reciprocal electric networks.

Propagation in normal, homogeneous media without field sources. Intrinsic propagation constant. Good dielectrics and good conductors. Introduction of plane waves as special solutions of Helmholtz's equations. Uniform transverse electromagnetic (TEM) waves, dissociated and evanescent waves. Reflection and refraction. Snell's law. Total reflection. Geometrical optics.

Integration  of Maxwell's equations in the presence of field sources with the aid of scalar and vector potentials. Integration of nonhomogeneous Helmoltz's equation by the Green's function method. General expressions of the electromagnetic field. Physical interpretation of potentials.

Elementary sources. Field radiated by a current element. Near and far fields of an elementary source. Finite-size sources. Equivalent moment. Far field of a finite-size source. Characteristic parameters of radiation: radiation intensity, directivity, gain and radiation function. Reception problem. Effective area. Transmission formula. First-approach evaluation of a radio link.

Free and guided electromagnetic propagation. Cylindrical structures and modes. Transverse electromagnetic (TEM) modes. Circuit representation of TEM propagation in an ordinary transmission line: voltage, current, capacity, characteristic impedance and admittance. Matching: load impedance and reflection coefficient, power delivered to the load. Transverse magnetic (TM) and transverse electric (TE) modes. Cut-off effect.

Readings/Bibliography

Vittorio Rizzoli, ‘Lezioni di campi elettromagnetici', Esculapio-Progetto Leonardo, 1998

Vittorio Rizzoli e Alessandro Lipparini, ‘Propagazione elettromagnetica guidata', Esculapio-Progetto Leonardo, 2002.

Teaching methods

The classroom lectures are mainly devoted to the treatment of the general aspects of the electromagnetic field propagation and of the analysis techniques of radio wave radiation and reception, as well as of guided wave transmission. The training hours are devoted to the solution of radio and cable link problems and to the study of the specific properties of the principal guiding structures.

Assessment methods

Discussion aimed at establishing the student's understanding of the general principles of electromagnetic propagation, as well as of the analysis techniques of the transmission of free-space and guided waves. Solution of problems on a radio or cable link.

Teaching tools

Two dedicated textbooks are available where the topics developed in the course are dealt with in detail.

Office hours

See the website of Alessandro Lipparini