The goal of the course is to provide the students with the theoretical knowledge and the methodologies necessary for modelling, analyzing, and designing communication systems relying on unguided electromagnetic wave propagation, both at radio and optical frequencies, in diversified terrestrial (e.g. point-to-point links, broadcast systems) and Earth-space scenarios (e.g. satellite communications - SatCom, global navigation satellite systems - GNSS). Moreover, the course provides the students with the instruments for understanding and applying the advanced technologies used in modern wireless links (e.g. SatCom systems). The course offers a balanced compromise between theoretical aspects and practical ones: first, the physical aspects of the phenomena are duly introduced; second, the theory behind them is addressed; third: a practical mathematical framework is derived useful for system design and analysis. The course also includes brief seminars providing an overview on “real world” systems (e.g. GNSS systems, experimental measurements).

Students will understand and learn:
• The physical concepts governing the unguided propagation of electromagnetic waves
• The mathematical framework for the analysis and design of wireless links operating at radio and optical frequencies
• The key elements and blocks composing complex communication systems relying on unguided electromagnetic wave propagation

Students will be able to:
• Analyse the performance of wireless links in diversified scenarios based on the system specifications
• Dimension the elements of a wireless link given key target requirements, such as the link availability and quality
• Apply the mathematical models learnt in the course

Students will be able to:
• Understand the fundamental tradeoffs that drive the design of wireless links
• Identify how the fundamental system limitations impact the design of a wireless link
• Judge which kind of wireless link and system (e.g. operational frequency, type of satellite orbit) is more suitable for a given scenario and service to be provided

Theory:
• Introduction: contents of the couse and main protagonists in the history of electromagnetic wave propagation and wireless communication systems.
• The electromagnetic spectrum: frequency bands and spectrum management.
• Main features of electromagnetic waves (frequency, wavelength, polarization, ...) and electromagnetic characterizations of materials (electric permittivity and magnetic permeability, conductivity, ...).
• Characterization of the electromagnetic propagation channel in terms of single and multiple wave components: direct, reflected, diffracted and diffused waves.
• Propagation in the ionosphere and impact on Global Navigation Satellite Systems (GNSS). Refraction, attenuation, Faraday rotation, phase and group delay.
• Propagation in the presence of the ground. The ground wave: direct, reflected, and evanescent waves, diffraction and Fresnel’s ellipsoids.
• Propagation in the non-ionized atmosphere (troposphere) and impact on radio relay links, as well as on Earth-space (HAPs, LEO, MEO, GEO satellites, Deep Space probes) links. Clear air propagation: refraction and ray bending, attenuation, scintillation, tropospheric scatter. Propagation through clouds. Adverse weather disturbances: attenuation, depolarization, electromagnetic interference due to hydrometeors.
• Atmospheric and extra-atmospheric noise sources: impact on the signal detection and some concepts on passive remote sensing.
• Statistical characterization of the radio channel and system design: the link budget. Fade mitigation techniques (e.g. site, frequency and time diversity, uplink power control, …).
• Free space optical wave propagation: the optical channel, transmitters and receivers. Advantages and limitations of FSO. Impairments due to hydrometeors (fog and clouds), and to clear air (turbulence). Applications: ground links and Earth to space links.

Practice:
• Problem solving on all the topics listed above.
• Presentation and use of the following software tools: propagation of plane waves through multi-layered materials, link budget in clear air, link budget for SatCom systems (including the impact of adverse weather conditions).
• Mentions to ITU-R recommendation, propagation series.

Trigonometry, calculus with complex numbers, basic notions on vectors and on electromagnetic fields, differential and integral calculus.

The exam includes a written test and an oral test:
• The written test consists in the solution of 4 problems relative to the topics listed above (e.g. ionospheric propagation and impact of rain on wireless links): past exams, with solutions, are available. This test aims at assessing the ability of the student to solve problems using the tools and concepts presented during the lectures. The test is open book: the student can use any material (e.g. personal notes, books) during the written test, but electronic devices that can connect to the web are not allowed.
• The oral test aims at evaluating the understanding of the physical concepts at the basis of the propagation of electromagnetic waves. The student will be typically asked to explain and discuss, in a conversational way, key physical concepts, rather than deriving analytical expressions.