Antennas and wave propagation

Subject description

Half-wave dipole, implementation of a directional antenna, Fraunhofer far field criteria, basic measurements of antenna parameters. Huygens source, antenna apertures, design of horn antennas, square phase error, phase-error correction with a collimating lens, lenses from artificial dielectrics, slow-wave structures. Parabolic mirror, computation of its focal point, selection of the section, mirror illumination, illumination efficiency, multiple-reflector antennas: Gregorian and Cassegrain. Antenna arrays and their design, array feeding networks, electrical array steering. Polarization of electromagnetic waves, definition of the antenna polarization, accounting for polarization mismatch in a radio link. Thermal noise, antenna noise temperature, natural noise sources on Earth and in the universe. Fresnel zones, propagation of radio waves in the presence of natural obstacles, mirrors and diffractors, radar cross-section, radar range equation. Propagation of electromagnetic waves in the Earth's atmosphere, absorption, refraction and reflection in the troposphere. Signal fading and channel distortion, fading statistics, link-failure probability, transmit and receive diversity.

The subject is taught in programs

Objectives and competences

Learning fundamental antenna characteristics. Learning directional antenna design. Learning radiation from distributed sources and thermal noise. Learning electromagnetic-wave propagation through the atmosphere and in the presence of obstacles. Learning reception fading and related countermeasures.

Teaching and learning methods

Lectures for theoretical background and laboratory experiments to practically confirm the theory working in a team environment.

Expected study results

After successful completion of the course, students should be able to:

– analyze the requirements and possibilities of a free-space radio link

– design simple antennas

– select an appropriate frequency band and corresponding antennas for a certain radio link

– build simple antenna arrays

– compute simple obstacle losses in a radio link

– consider tropospheric and ionospheric effects in a radio link

– calculate the probabily of signal loss in a radio link

– compute the capacity of a MIMO radio link

Basic sources and literature

  1. J. D. Kraus, Antennas, McGraw-Hill, New York, 1950.
  2. J. Budin, Razširjanje radijskih valov, FE, Ljubljana, 1975.
  3. M. Vidmar, Sevanje in Razširjanje, Laboratorijske vaje, FE, Ljubljana 1998.

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