ANTENNAS AND RADIOPROPAGATION

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, 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 with single/multi-layer metallo-dielectric structures, anisotropic media, cold plasma etc.

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.
• Continuity equations and conservation laws.
• Time-domain constitutive relations.
• Boundary conditions for electromagnetic fields.
• Frequency-domain electromagnetic fields and phasors.
• Time-domain and frequency-domain Poynting theorem. Poynting vector. Energy balance.
• Time-domain and frequency-domain Uniqueness theorem.
• Constitutive relations for non-polar dielectrics: Lorentz model.
• Constitutive relations for conductors.
• Constitutive relations for cold collisionless plasma.

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.
• Uniform and non-uniform plane waves: classification.
  • Uniform plane waves in non-dispersive and non-dissipative media.
  • Non-uniform plane waves in non-dispersive and non-dissipative media (TE and TM waves).
  • Uniform plane waves in non-dispersive and non-dissipative media.
• Plane wave spectrum and wavenumber domain.
• Dispersive and non-dispersive media. Phase velocity.
• Group velocity and wave-packets: beat, 1D and 3D wave-packets.

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 a generic load: fundamental parameters.
  • Line voltage and currents along transmission lines.
  • Reflection coefficient, VSWR, impedance calculation, power.
  • Special case: transmission line terminated on its characteristic impedance.
  • Special case: open-circuited transmission lines.
  • Special case: short-circuited transmission lines.
• Smith chart and conformal mapping.
• Maximum power transfer and impedance matching.
• Quarter-wavelength transformer impedance matching.
• S.C. series stub impedance matching.
• O.C. series stub impedance matching.
• S.C. shunt stub impedance matching.
• O.C. shunt stub impedance matching.

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

• Plane wave incidence on a single planar dielectric interface.
  • First and second Snell laws from Maxwell equations.
  • Normal incidence: TEM case.
  • Oblique incidence: TE and TM cases.
  • Fresnel coefficients.
• Detailed analysis of total reflection and Brewster angle.
• 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 fields: Luneburg-Klein series, geometrical optics, Fermat principle, eikonal and ray equations.

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.
• Physical mechanism of radiopropagation versus frequency.

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 Antennas:

[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).