Project Description
Obiettivi
Following the course of Electromagnetic Fields, this teaching aims to provide the principles, models and basic tools for the representation and design of the most common classes of radiating elements, both in isolated configuration and in array mode up to the description of a complete wireless communication link.
KNOWLEDGE AND UNDERSTANDING:
Students will have understood the principles and the mathematical representation of irradiation and reception of electromagnetic waves through antennas. They will also be able to demonstrate that they have acquired the methodologies for digital simulation of the structures studied with electromagnetic Computer Aided Design (CAD) tools.
APPLY KNOWLEDGE AND UNDERSTANDING:
Students will be able to select the most suitable radiating element for the specific class of applications (broadcasting communications, directive, broadband). They will also be able to qualitatively and quantitatively evaluate the performances, the potentialities and the possible critical issues with reference to the performance parameters (gain, matching, bandwidth, radiation patter, size).
Finally, they will be able to apply the proposed electromagnetic solver to the modeling of simple antenna configurations.
AUTONOMY OF JUDGMENT:
Students will acquire the ability to integrate the knowledge provided with those found autonomously through access to scientific literature and correctly select the most appropriate analytical and design options to address the proposed problems.
COMMUNICATION SKILLS:
Students will be able to illustrate in a synthetic and analytical way both the basic themes and the vocational ones object of the course making use of equations and schemes.
LEARNING SKILLS:
Students will have acquired the ability to read and understand texts and scientific articles in English for in-depth study of the topics covered but also to extend their own knowledge of the subject independently to issues not directly addressed in the course and connected to the constant technological evolution of wireless systems.
Programma
The elementary antennas and the distributed sources and their performance parameters are then introduced. A numerical method is then described for the digital representation of computer radiating elements and how to use a commercial solver based on this method is explained. We then move on to wireless systems for broadcasting applications based on wire antennas and then to array configurations for applications to point-to-point communications, radar systems and adaptive cellular communication.
The following section introduces antennas for personal communications (mobile phones, notebooks, wearable devices based on microstrips) and describes the entire communication system.
In the last 3 CFUs (not mandatory for the 6CFU course) broadband and ultra-wide communication antennas based on volumetric and self-scaling devices are introduced and finally reflector antenna systems are described for directive communication over long distances.
The frontal lessons are completed by several interactive numerical exercises also with the use of electromagnetic simulators
in Details:
1. INTRODUCTION TO ANTENNAS (2h)
Essential chronology. Radiation mechanisms. Types of antennas.
2.ANTENNA BASICS (4h)
Introduction to transmission lines.
Sources of electromagnetic field: impressed, equivalent, images.
Radiation Potentials.
Green Function.
3. ELEMENTARY ELECTRIC AND MAGNETIC DIPOLES (4h)
Static and dynamic regimes (reactive and radiating field).
Hertzian dipoles.
4. DISTRIBUTED SOURCES (4h)
Fraunhofer and Fresnel radiation regions.
Propagation as the two-dimensional spatial Fourier Transform.
Radiation parameters: effective length, radiation intensity, directivity, gain. efficiency, beamWidth, polarization.
Equivalent-circuit parameters: input impedance, reflection coefficient, bandwidth, realized gain.
5. COMPUTED AIDED ELECTROMAGNETICS (8)
Integral equations of the Electromagnetic Scattering: wire scatterers (Pocklington, Hallen equations), extended scatterers.
Method of Moments: theory and FEKO computer solver.
6. BROADCASTING ANTENNAS (10)
Half-wave dipole antenna: transmission-line equivalent current, input impedance, series and parallel resonance, radiation pattern, beamwidth, directivity.
Folded dipoles, T-match, Gamma Match.
Quarter-wave monopole: Marconi antenna.
Loop antennas: transmission-line equivalent, small loop, large loop, series and parallel resonance, radiation pattern, beamwidth, directivity.
Frequency tuning, feeding techniques.
7. ARRAYS AND BEAMSHAPING (12)
Arrays of Antennas: Array factor, multiplication principle, total gain, taper efficiency.
Uniform linear arrays: visibility windows, radiation pattern, beamwidth, phased beam, broadside and endfire arrays, electronic beam scanning, greating lobes, arrays of dipoles, beamforming networks (tree and bus).
Uniform two-dimensional array: beam scanning.
Non-Uniform array synthesis: binomial illumination, Tchebyshev illumination, Fourier beam-shaping synthesis, Alternate Protection synthesis
8. ANTENNAS FOR PERSONAL DEVICES (12)
The microstrip. The slot.
Integrated Patch antennas: transmission-line model, impedance matching, substrates, radiation pattern, efficiency and bandwidth, PIFA antennas.
Miniaturization techniques: slots, shorting pins, meandering.
Broadbanding: multi-layer antennas, stacked configurations.
Circular polarization: double-ports, single port configuration.
9. WIRELESS COMMUNICATION LINKS (4)
Antennas in receiving mode: Friis formula, radar cross-section, radar equation.
Introduction to Radiofrequency Identification.
3 CFU (mandatory only for the 9 CFU course)
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10. BROADBAND ANTENNAS (15)
Thick dipoles: biconical antennas, Bow-tie, cylindrical antennas.
Self-scaling antennas: log-periodic antenna, logarithmic spiral, fractals antennas.
11. HIGH GAIN ANTENNAS (15)
Yagi-Uda array.
Aperture antennas: Fourier transform representation, uniform rectangular aperture, uniform circular aperture, Array equivalence.
Reflector Antennas: ray-optic approximation, parabolic reflectors, system gain. Dual-reflectors and offset antennas.