ANTENNAS AND RADIOPROPAGATIONAnno accademico 2022/2023 - Docente: GINO SORBELLO
Risultati di apprendimento attesi
Knowledge and understanding:
The course aim is to provide basic concepts and techniques of Applied Electromagnetics, together with its most relevant applications in electronics engineering. Moving from the unavoidable theoretical background (basically Maxwell's Equations and their solutions) required for deeply understanding the generation and propagation of electromagnetic waves in different environments.
Applying knowledge and understanding:
The course of Antennas and Radiopropagation gives students basic tools for designing transmission lines, radio-links, antennas, as well as concepts to evaluate quantitatively the interaction of electromagnetic fields and different environments of interests for electronics engineers (single/multi-layer metallo-dielectric structures, anisotropic media, cold plasma etc.), together with the design of basic antenna systems.
At the end of the course, students will be able to properly apply the presented tools and methodologies to solve problems on electromagnetic field radiation and propagation, by carefully considering which theoretical model (among those presented during the course) is the most suitable to obtain accurate solutions.
At the end of the course of Antennas and Radiopropagation, students will be required to properly describe all the fundamental concepts introduced throughout the course. Moreover, they will need to to apply basic techniques and methodologies to solve exercises on electromagnetic field propagation and radiation.
Students will be able to improve their knowledge on the theory of electromagnetic fields, of antennas and radiopropagation, both through the deepening of reference textbooks and also through papers in specialized scientific journals, as well as through new ideas offered by the organized seminars.
Modalità di svolgimento dell'insegnamento
Contenuti del corso
Overview of orthogonal curvilinear coordinates and differential operators
Gradient, divergence, curl, directional derivative, Laplacian (scalar and vector).Overview of orthogonal curvilinear coordinates, metric coefficients, differential operators in special cases (Cartesian, cylindrical, spherical).Divergence and curl theorems. Green identities. Frequently-used vector identities.
Time-domain Maxwell equations. Charges in electromagnetic fields and Lorentz force. Global and local forms of Maxwell equations. Continuity equations and conservation laws. Constitutive relation. Boundary conditions for electromagnetic fields. Frequency-domain electromagnetic fields and phasors.Time-domain and frequency-domain: energy balance. Uniqueness of the solution: time-domain and frequency-domain. Definition of SAR. Polarization: linear, circular and elliptical.
Wave equation and plane waves
Solution of homogeneous Helmholtz equation in Cartesian coordinates: plane waves. Equi-phase and equi-amplitude surfaces: fundamental relations. Classification of plane waves. Plane wave spectrum and wavenumber domain. Dispersive and non-dispersive media. Wave-packets. Phase and group velocities.
Transmission lines and matching techniques
Introduction to transmission lines: derivation of line parameters from Maxwell equations. Time-domain and frequency-domain telegraphers' equations. Solutions in terms of traveling and standing waves. Transmission lines with small losses. Transmission lines terminated on generic loads: fundamental parameters. Smith chart. Maximum power transfer, impedance matching by quarter-wavelength transformer and stubs.
Reflection and transmission of plane waves.
Normal incidence. Plane wave incidence on a single planar dielectric interface; Snell laws and Fresnel coefficients. Brewster angle. Single interface air-good conductor: normal incidence (TEM). Skin depth. Leontovich impedance boundary condition.
Radiation theory and antennas
Electrodynamic potentials and Lorentz gauge invariance. Electromagnetic field souces: time-varying charges and currents. Overview of electrodynamic potentials. Radiation condition at infinity (or Sommerfeld condition). Non-homogeneous Helmholtz equation and free-space scalar Green function. Scalar Green function approximations versus distance: reactive field, Fresnel and Fraunhofer regions. Detailed analysis of elementary dipole radiation in free-space and far-field approximation. Radiation of a small loop. Isotropic, directive and omni-directional antennas.
Transmitting and Receiving Antennas
Fundamental parameters of transmitting antennas. Calculation of fundamental antenna parameters for dipoles and loops. Detailed analysis of thin wire-antennas. Image theorem and radiation in presence of a ground plane. Monopole antennas and fundamental parameters. Reciprocity theorem. Fundamental parameters of receiving antennas (relating transmitting and receiving antenna parameters). Friis formula for radio-links. Elements of radiopropagation: direct, refracted, scattered, surface, ionospheric waves.
Laboratory, simulations and CAD
Measurements of Fresnel coefficients. Pyton/MATLAB scripting for applied electromagnetics typical problems. Antenna design by using CAD softwares. Antenna measurements.
Testi di riferimento
1. S. J. Orfanidis, "Electromagnetic Waves and Antennas".
2. G. Franceschetti, Electromagnetics, Theory, Techniques, and Engineering Paradigms, Springer.
3. C. G. Someda, "Electromagnetic Waves", CRC Press.
4. F. T. Ulaby, U. Ravaioli Fundamentals of Applied Electromagnetics (7th Edition), Pearson Education.
Programmazione del corso
|1||Overview of orthogonal curvilinear coordinates and differential operators||1, 4|
|3||Wave equation and plane waves||2, 3|
|4||Reflection and transmission of plane waves.|
|5||Radiation theory and antennas||3|
|6||Transmitting and Receiving Antennas||1, 3, 4|
|7||Laboratory, simulations and CAD||notes|