ANTENNE E RADIOPROPAGAZIONE

Maxwell's equations and general principles

Introduction to electromagnetism. Historical Background, importance and applications. Maxwell's equations in the time domain: integral form and differential form. Charge and current density. Lorentz force. Boundary conditions at surfaces of discontinuity. Maxwell's equations in sinusoidal regime. Phasor representation. Polarization of the electromagnetic field. Constitutive relations. Material properties. Dispersive media. Constitutive relation for a cold plasma without collisions. Energy of the electromagnetic field. Poynting vector. Uniqueness of the solution (time domain and phasor domain). Resonance conditions. Radiation conditions at infinity.

Propagation

Plane-wave solution. Phase and group velocity. Plane waves: classification. Reflection and transmission at plane interfaces. Normal incidence. Good conductor of case: skin depth. Snell low. Fresnel coefficients for parallel (TM) and orthogonal (TE) polarization. Total transmission (Brewster angle) and total reflection (critical angle). Transmission in a lossy medium. Leontovic condition. Propagation through the atmosphere (surface wave propagation and by ionospheric wave).

Transmission lines.

Metallic waveguides with cylindrical symmetry. Separation of longitudinal transverse components. TEM modes. Equivalent voltages and currents on a transmission line. Telegrapher's equations (time and frequency domain). Phase velocity. Primary and secondary parameters of a transmission line. Stationary and progressive solutions. Reflection coefficient. Impedance (definition). Impedance transport. Voltages and currents on a transmisison line: matched load, reactive load, generic load. Voltage standing wave ratio (VSWR). Impedance matching: quarter wavelength transformer, single and double stub. Resonance on transmission lines, series resonance and parallel resonance, resonance conditions. Losses in transmission lines. Lines with small losses. Propagation of a narrow-band signal, the group velocity.

Waveguides

TE and TM modes. Helmholtz equation or for potential. Eigenvalues ​​, orthogonality of the eigenfunctions . Modal expansion. Consequences of orthogonality for total power flowing. Equivalent transmission lines. Dispersion and cutoff frequencies in waveguide. Fundamental and higher modes. Calculation of the TE and TM modes in a rectangular waveguide. Dimensions of the rectangular waveguide fundamental mode TE10.

Electromagnetic potentials. Gauge transformations. Magnetic vector potential. Elementary electric dipole in a homogeneous medium. Far field contitions. Circular loop. Thin linear antennas: half wave antenna. Antennas parameters: effective height, input impedance and the radiation resistance. Directivity, gain. Reception. Polarization matching and impedance matching. Effective area. Aperture antennas. Friis transmission formula. Image sources (image currents).

Laboratory

Study and design of waveguides and linear antennas using numerical methods; measurement of the resonance frequency and radiation pattern of antennas*. Plane waves: Snell laws/ Fresnel coefficients.

MASTER DEGREE THESIS: The topics marked with an asterisk (*) can be matter of thesis work.