ANTENNAS AND RADIOPROPAGATION

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.

Making judgements:

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.

Communication skills:

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.

Learning skills:

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.

The course includes theoretical lectures, laboratories, and numerical simulations (CAD).

Learning Assessment:

Written and oral exams.

Learning assessment may also be carried out on-line, should specific conditions require it.

0) Overview of orthogonal curvilinear coordinates and differential operators

• First and second order 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.

1) Maxwell equations (MEs) and foundations of classical electrodynamics

• Time-domain Maxwell equations.
• Charges in electromagnetic fields and Lorentz force.
• Global and local forms of Maxwell equations.
• Continuity equations and conservation laws.
• Constitutive relations (Lorentz model for dielectrics, conductors, cold plasma)
• Boundary conditions for electromagnetic fields.
• Frequency-domain electromagnetic fields and phasors.
• Time-domain and frequency-domain Poynting theorems. Poynting vector. Energy balance. (*) Definition of SAR.
• (*) Time-domain and frequency-domain Uniqueness theorem.

2) Wave equation and plane waves

• Inhomogeous wave (and Helmholtz) equation from Maxwell equations.
• Electrodynamic potentials and Lorentz gauge invariance.
• Solution of homogeneous Helmholtz equation in Cartesian coordinates: plane waves.
• Plane wave polarization: linear, circular and elliptical.
• Equi-phase and equi-amplitude surfaces: fundamental relations.
• Classification of plane waves and "complex waves".
• Plane wave spectrum and wavenumber domain.
• Dispersive and non-dispersive media. Wave-packets. Phase and group velocities.

3) 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: Heaviside conditions.
• Transmission lines terminated on generic loads: fundamental parameters.
• Smith chart and conformal mapping.
• Maximum power transfer, impedance matching by quarter-wavelength transformer and stubs.

4) Reflection and transmission of plane waves in multilayer planar interfaces

• Plane wave incidence on a single planar dielectric interface; Snell laws and Fresnel coefficients.
• Detailed analysis of total reflection and Brewster angle. (*) Hints on dielectric waveguides.
• Equivalent TE/TM transmission line formalism for the analysis of multilayer planar interfaces.
• Single interface air-good conductor: normal incidence (TEM). Skin depth. Leontovich impedance boundary condition.
• Analysis of multilayer structures by using ABCD matrices.
• Brief overview of high-frequency approx of EM field (ray equation, Geometrical Optics).

5) Radiation theory and antennas

• 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.
• Duality theorem in electromagnetics. Application to the radiation of a small loop.
• Isotropic, directive and omni-directional antennas.

6) 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.
• (*) Fundamental theorem relating transmitting and receiving antenna parameters.
• Friis formula for radio-links.
• Monostatic RADAR equation.
• (*) Design of satellite links: antenna noise temperature, G/T, EIRP.
• Elements of radiopropagation: direct, refracted, scattered, surface, ionospheric waves.

7) Laboratory, simulations and CAD

• Measurements of Fresnel coefficients.
• MATLAB scripting for applied electromagnetics typical problems.
• Antenna design by using CAD softwares.

Foundations of Applied Electromagnetics:

[1] C. A. Balanis, "Advanced Engineering Electromagnetics", Wiley.

[2] G. Franceschetti, "Campi Elettromagnetici", Bollati Boringhieri.

[3] G. Gerosa, P. Lampariello, "Lezioni di Campi Elettromagnetici", Edizioni Ingegneria 2000.

[4] J. Van Bladel, "Electromagnetic Fields", 2nd edition, IEEE Press Series on EM Wave Theory.

[5] C. G. Someda, "Electromagnetic Waves", CRC Press.

Foundations of Antenna Theory

[6] C. A. Balanis, "Antenna Theory: Analysis and Design", Wiley.

[7] F. S. Marzano, N. Pierdicca, "Fondamenti di Antenne", Carocci.

[8] S. J. Orfanidis, "Electromagnetic Waves and Antennas", vol. II (Antennas).