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Takács György

Infocommunication systems Infokommunikációs rendszerek Lecture 3. előadás Radio transmission Rádiós átvitel. Takács György. Radio transmission media. Frequency bands and wave propagation modes Terrestrial radio connection Satellite communication In door radio connection.

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Takács György

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  1. Infocommunication systems Infokommunikációs rendszerekLecture 3. előadásRadio transmissionRádiós átvitel Takács György infokom. 3. ea. 2012. szept. 23.

  2. Radio transmission media • Frequency bands and wave propagation modes • Terrestrial radio connection • Satellite communication • In door radio connection infokom. 3. ea. 2012. szept. 23.

  3. Media characteristics • Transmission parameters (path loss, delay, fading, radio interferences) • Reliability and availability - equipment and propagation parameters (lightning, snow, rain, fog, smoke) • Openness – interferences - privacy infokom. 3. ea. 2012. szept. 23.

  4. Is radio communication a technical issue (1)? • Radio communications use open and common media. Using a radio frequency means consuming. So management of radio frequency is inevitable. • Using a radio frequency means a kind of environment pollution! Frequency police? • Radio frequencies are limited resources. The „good” frequencies are already consumed. Frequency fees! NMHH. • Propagation of radio waves do not consider political borders! Frequency management is a typical international process. (CCIR, ITU-R) infokom. 3. ea. 2012. szept. 23.

  5. Is radio communication a technical issue (2)? • Radio frequencies have considerable physiological effect! • Antennas are considered as special constructions. Local municipalities regulate construction rules and issue building licences. • Satellite positions are limited resources too. The „good” positions are consumed. • Differential equations of electromagnetic wave propagation are quite simple – in the case of plane wave and free space. Solutions in real geographic situations (among hills, valleys, buildings or especially inside buildings) are extremely difficult. infokom. 3. ea. 2012. szept. 23.

  6. Frequency bands and wave propagation modes • LF (30-300kHz) • MF (300-3000kHz) • HF (3-30 MHz) • VHF (30-300 MHz) • UHF (300-3000MHz) • SHF (centimetric waves, 3-30GHz) • EHF (millimetric waves, 30-300GHz) infokom. 3. ea. 2012. szept. 23.

  7. Propagation modes and antennas LF MF infokom. 3. ea. 2012. szept. 23.

  8. infokom. 3. ea. 2012. szept. 23.

  9. Propagation modes and antennas HF infokom. 3. ea. 2012. szept. 23.

  10. infokom. 3. ea. 2012. szept. 23.

  11. Propagation modes and antennas UHF VHF SHF EHF infokom. 3. ea. 2012. szept. 23.

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  16. in free space (ε0,µ0): plane-wave solution 1. electric and magnetic field vectors are perpendicular 2. ratio of their amplitudes is a constant and called as free-space wave impedance infokom. 3. ea. 2012. szept. 23.

  17. characteristic impedance Reflection coefficient infokom. 3. ea. 2012. szept. 23.

  18. Free space radio link (LOS) PT transmitted power Ae effective area of antenna G gain of antenna λ wavelength d distance infokom. 3. ea. 2012. szept. 23.

  19. infokom. 3. ea. 2012. szept. 23.

  20. Example by GSM mobile system Pr=kPT/d2 d=30m Base station P=50W Pr=k×0,0555 d=3cm P=5W Pr=k×5555 100000× infokom. 3. ea. 2012. szept. 23.

  21. Polarization: • Property of a radiated electromagnetic wave describing the time varying direction and relative magnitude of the electric-field vector • In general the field is elliptically polarized • Linear and circular polarizations are special cases infokom. 3. ea. 2012. szept. 23.

  22. Reflection • The amplitude, phase and polarization of the reflected wave is determined by the material parameters of the medias and the surface irregularity. infokom. 3. ea. 2012. szept. 23.

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  26. Propagation with direct and reflected waves and reflected only waves infokom. 3. ea. 2012. szept. 23.

  27. RADIO FOR MOBILES SENDER RECEIVER Without FADING infokom. 3. ea. 2012. szept. 23.

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  38. „Good” frequencies? Bandwidth issues? • Low attenuation (loss) • High bandwidth • Beaming – circular characteristic • Cheap or free • No interference • Exclusive usage • „Good” frequencies are not existing -- Only compromise of limitations infokom. 3. ea. 2012. szept. 23.

  39. Radio link types • Point-point connections • Point multipoint connections • Cellular systems infokom. 3. ea. 2012. szept. 23.

  40. Optically visible loop The surface of the earth 30-50 km because the spherical earth Terrestrial microwave connections infokom. 3. ea. 2012. szept. 23.

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  43. Centrifugal force Mass of the satellite, kg Mass of the earth Gravitational constant Speed of the satellite, m/s Gravitation force Geostationary satellite characteristics infokom. 3. ea. 2012. szept. 23.

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