ANTENNAS AND PROPAGATION Introduction Carlos A. Fernandes Antennas and Propagation - Master in Aerospace Engineering
1.1 Electromagnetic radiation What is electromagnetic radiation? ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 2
1.1 Electromagnetic radiation Sources of EM radiation Sol fonte natural Sol, ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 3
1.1 Electromagnetic radiation Sources of EM radiation Power lines ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 4
1.1 Electromagnetic radiation Sources of EM radiation Telecom antennas ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 5
1.1 Electromagnetic radiation Sources of EM radiation Home appliances ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 6
1.1 Electromagnetic radiation Sources of EM radiation Light bulbs ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 7
1.1 Electromagnetic radiation Sources of EM radiation I f -red d devices d i Infra InfraANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 8
1.1 Electromagnetic radiation Sources of EM radiation X-ray devices ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 9
1.2 Brief historical account Static electricity (known since 600 AC) Magnetism Electric field (static) ti Magnetico field (static) ti E [Volt/m] H [Ampere/M] EeHha have space orientation ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 10
1.2 Brief historical account André--Marie Ampère André Michael Faraday I 1823 - Magnetic field produced byy static electrical current 1831 - Electric current produced y g magnetic g byy a time varying field ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 11
1.2 Brief historical account Maxwell, 1873 Hertz, 1887 Time varying Electric and Magnetic fields are coupled to each other and propagate without the need for a material medium. ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 12
1.2 Brief historical account Spark gap transmitter (Circuit similar to Hertz s) Receiver (resonant loop) ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 13
1.2 Brief historical account Marconi Antenna Why is it so large? ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 14
1.2 Brief historical account Poldhue, Cornualha ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 15
1.2 Brief historical account Forerunners in the path of electromagnetics 600 AC - Thales from Mileto 1600 - William Gilbert 1750 - Benjamin Franklin 1855) 1785 - Charles Coulomb Karl Gauss (1777-1855) 1800 - Alessandro Volta Cauchy (1789-1857) 1819 - Hans Oersted Riemann (1826-1866) Fourier (1768-1830) 1830) 1823 - Andre Ampere Green (1793-1841) 1831 - Michael Faraday Stokes (1819-1903) 1832 - Joseph Henry (telégrafo) Heaviside (1850-1925) 1873 - James Maxwell ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 16
1.2 Brief historical account First steps for radio and wireless communications 1887 - Heinrich Herz (experimental proof of Maxwell equations) 1895 - Marconi, Popov (application to communications) 1901 First transatlantic radio transmission 1903 Start of commercial wireless telegraphy service 1913 Invention of the triod 1923 First voice transmission through radio waves 1930 Discovery of cosmic radiation 1945 Arthur C. Clark proposes the use of satellites 1945 Invention of the solid-state transistor ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 17
1.3 Wave concept v (z, t) ) = cos(ωt kz) ) ω= 2 π f phase k = ω/c/ v(z,t) f=100 MHz z [m] ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 18
1.3 Wave concept v (z, t) ) = cos(ωt - kx - kz) ) ω= 2 π f phase k = ω/c/ x [m] f=100 MHz z [m] z [m] ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 19
1.3 Wave concept v (r, t) ) = cos(ωt - kr)/ r ω= 2 π f fase k = ω/c/ x [m] f=100 MHz (For spherical wave the amplitude decreases with 1/r) z [m] z [m] ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 20
1.3 Electromagnetic spectrum Microwaves Vi isíble X Rays Radiowaves Infra-red UV γ Rays Frequêncy [Hz] 10 2 10 4 10 6 10 8 10 10 10 12 10 14 10 16 10 18 10 20 10 22 10 6 10 4 10 2 1 10-2 10-4 10-6 10-8 10-10 10-12 Wavelength [m] Non ionizing radiation, TV ones FM Mo obile ph lites Satel Direct perceptio on Ionizing radiation Med dicin dia agn. atam. Med. tre ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 21
Regresso ao Índice ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 22
William Gilbert First systematic experiments with electricity and magnetism Invention of the electroscope for measuring electrostatic t ti fields. Work reported in De Magnete Regresso ao slide anterior ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 23
Establishment of the law of charge conservation. Identification of positive and negative charges. Invention of the lightning rod. Regresso ao slide anterior ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 24
Charles Coulomb Experiments and establishment the Coulomb Law ; F = K Q 1Q 2 r 2 Regresso ao slide anterior ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 25
Andre Ampere Invention of the solenoid to produce magnetic fields Experiments and establishment t of the law I1 I2 F =α r Regresso ao slide anterior ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 26
Michael Faraday Demonstration that a varying magnetic filed can produce an electric current. Regresso ao slide anterior ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 27
James Maxwell Establishment of the formal relation between electric and magnetic fields. Regresso ao slide anterior ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 28
Heinrich Hertz Experimental confirmation of Maxwell s equations. Regresso ao slide anterior ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 29
Guglielmo Marconi Demonstration of the potential of electromagnetic waves for longdistance wireless communications Regresso ao slide anterior ANTENNAS AND PROPAGATION - MAero carlos.fernandes@lx.it.pt 30