ANTENNAS AND RADIOPROPAGATION

The lectures aim to give the conceptual tools and the techniques for the description of the classical electromagnetic phenomena with particular reference to the irradiation and propagation of electromagnetic signals. The aim is the acquisition of basic methodologies for the study, analysis and sizing of guiding structures and antennas

The course includes both lectures and experimental laboratories to elaborate on the contents of the lessons.

Required prerequisites:

Basic knowledge of differential and integral calculus. Phasors and vectors. Differential operators. Concept of charge, current, electric and magnetic field. Techniques to study lumped circuits.

1) Maxwell's equations:

• Maxwell's equations in time domain.

• Charge.

• Lorentz force.

• Constitutive relations.

• Boundary conditions.

• Conservation Laws. Energy density and energy flow.

• Time-harmonic electromagnetic fields.

• Classical models for dielectrics, conductors and plasma.

• Causality.

2) Simple solutions of Maxwell's equations: plane waves

• Uniform plane waves in lossless media (time-domain).

• Monochromatic plane waves (frequency-domain).

• Plane waves in lossy media (frequency-domain).

  • Propagation in weakly-lossy dielectric;

  • Propagation in good conductors: skin effect.

• Wave polarization.

• Plane waves classification: uniform, evanescent and dissociated plane wave.

• Dispersion. Group velocity and energy velocity.

3) Transmission Lines, Matching Techniques and Waveguides

• TEM propagation in transmission lines.

• Distributed circuit model of a transmission line.

• Characteristic impedance, reflection coefficient, VSWR.

• Transmission lines:

  • Coaxial cable.

  • Two-wire line.

  • Microstrip line.

• Matching techniques.

• Helmholtz decomposition in waveguides.

• Classification of modes: TE, TM and TEM.

• Rectangular waveguide: TE/TM modes, power transfer, group velocity.

• Circular waveguide.

4) Reflection and Transmission of plane waves

• Planar interface between two media: TE/TM modes.

• Reflectionless slab and planar multi-layer structures.

• Equivalent transmission line model for TE/TM propagation in multi-layer slabs.

• Fermat’s principle and ray tracing.

5) Radiation Theory and Antennas

• Charges and currents as sources of EM fields.

• Retarded potentials and signal propagation.

• Time-harmonic radiation theory: potentials.

• Radiation Fields. Radiation vector.

• Plane-wave spectrum (PWS).

• Antenna relevant parameters: pattern, gain, directivity, effective area, polarization.

• EM Field radiated by an elementary dipole.

• Wire and loop antennas.

• Aperture antennas: description and relevant antenna parameters.

• Patch antennas.

6) Transmitting and Receiving Antennas

• Coupled antennas.

• Friis’ Formula.

• Polarization matching.

• Antenna Noise Temperature and data rate limit.

7) Laboratory

• Study and design of waveguides and antennas using numerical CAD.

• Antenna resonance and pattern measurement; RADAR.

• Plane waves: Fresnel coefficients measurement.

Textbook Information

1. S. J. Orfanidis, "Electromagnetic Waves and Antennas".

2. C. G. Someda, "Electromagnetic Waves", CRC Press.

3. F. T. Ulaby, U. Ravaioli Fundamentals of Applied Electromagnetics (7th Edition), Pearson Education

4. R. Sorrentino e G. Bianchi, "Microwave and RF Engineering", John Wiley & Sons 2010