# GUIDED WAVE PROPAGATION

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Versione italiana
2022/2023
Teacher
STEFANO TRILLO
Credits
6
Didactic period
Secondo Semestre
SSD
ING-INF/02

#### Training objectives

This is an advanced course of electromagnetic propagation aimed at understanding the engineering problems and the related methodologies of solution at the base of the propagation in guiding structures both at microwave and optical frequencies.

The main knowledge that will be gained is:
- The mathematical methods at the base of the guided electromagnetic propagation with particular reference to the concept of modes of propagation and their features;
- Knowledge of the geometry of main waveguides, resonators, and other major microwave components;
- Basic elements of propagation in optical fibers;
- Layout of a fiber optic link.

The main skills (i.e. the ability to apply their knowledge) will be:
- Know how to design waveguides and more complex structures that support the propagation of microwaves;
- Be able to set up a bench for measurements at microwave frequencies and to analyze the relative data;
- Know how to design point-to-point communication links based on optical fibers.

#### Prerequisites

Basic knowledge of mathematics (analysis) and physics (electromagnetics). Fundamental of the electromagnetic propagation based on Maxwell equations.

#### Course programme

Introduction to guiding structures. Motivations to wave-guiding e.m. fields. Links with the theory of circuits. Radiation. Efficiency of radio link. Methods to study waveguides. General concept of guided mode. Metallic guides for microwaves. Solution of homogeneous Helmholtz equation in cylindrical coordinates. TE, TM e TEM modes. Equivalent transmission lines. Boundary conditions. Eigenvalue equations and methods of solution. Attenuation and dispersion features of guided modes. Examples: rectangular and circular cross-section waveguides, coaxial cables. Effect of losses. Microstripes, quasi-TEM mode and their characteristics.
Resonators: Resonant circuits (RLC). Cylindrical resonators: resonant frequencies and modal profiles. Effect of losses. Quality factor. Passive junctions.
Dielectric waveguides and optical fibers: Guiding in inhomogeneous dielectrics. Geometrical and exact approach to propagation in slab waveguides: dispersion diagram, modal profiles, and cut-off. Optical fibers. Losses and dispersion in fiber links. Detection of optical signal with thermal and shot noise. Receiver sensitivity. Limitation to performances of fiber links.

#### Didactic methods

Theoretical lessons with illustrative exercises and laboratory (microwave and/or optics).

#### Learning assessment procedures

The examination is aimed at verifying the degree of achievement of learning objectives.
The exam consists of an oral test with (typically) three questions on the main topics with possible verification of the ability to link between them. One of the questions might concern the solution of a short exercise.