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Satellite Communications A Part 3

EEM.scmA. Satellite Communications A Part 3. Link planning / budgetting -Professor Barry G Evans-. Link budget & system planning. Mobile System. Performance. (i) QoS – b.e.r. 10-4 if speech 10-6 – 10-8 data (extra coding) (ii) Availability 95% Channel conditions. Basic Transmission.

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Satellite Communications A Part 3

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  1. EEM.scmA Satellite Communications APart 3 Link planning / budgetting-Professor Barry G Evans- SatComms A - part 3 - B G Evans

  2. Link budget & system planning SatComms A - part 3 - B G Evans

  3. Mobile System SatComms A - part 3 - B G Evans

  4. Performance • (i) QoS – b.e.r. • 10-4 if speech • 10-6 – 10-8 data (extra coding) • (ii) Availability • 95% • Channel conditions SatComms A - part 3 - B G Evans

  5. Basic Transmission SatComms A - part 3 - B G Evans

  6. Carrier Transmission Budget-Antenna Gain- The antenna gain is defined as the ratio of the power per unit solid angle received/radiated by the antenna in a given direction to the power per unit solid angle received/radiated by an isotropic antenna supplied with the same power. SatComms A - part 3 - B G Evans

  7. Basic Transmission SatComms A - part 3 - B G Evans

  8. Basic Transmission SatComms A - part 3 - B G Evans

  9. Antenna radiation pattern Antenna radiation pattern = gain variations as a function of the angle  relative to boresight SatComms A - part 3 - B G Evans

  10. Transmitted power in a given direction SatComms A - part 3 - B G Evans

  11. Predicted coverage areas for the HOTBIRD satellites • Superbeam • Widebeam • (courtesy of EUTELSAT) SatComms A - part 3 - B G Evans

  12. Effective isotropically radiated power (EIRP) SatComms A - part 3 - B G Evans

  13. Exercise (1) - Carrier Transmission Budget • Given • Power fed to antenna: PT = 10W • Antenna gain (at boresight): GTmax = 40dB • Distance: R = 36000km (earth to geostationary satellite • Calculate • Transmitter EIRP in dB(W) • Flux density at receiver in dB(W/m2) SatComms A - part 3 - B G Evans

  14. Down Path SatComms A - part 3 - B G Evans

  15. GEO - Geometry SatComms A - part 3 - B G Evans

  16. Earth station from the geostationary orbit • Satellite • Height h above the equator • Sub-satellite point, longitude ΦS • Earth station • Latitude E, longitude ΦE • Relative longitude satellite = (ΦE – ΦS) = ΦES SatComms A - part 3 - B G Evans

  17. Exercise (2) – Carrier Transmission Budget • Given • Uplink frequency = 14GHz • Eart station • Power fed to the antenna: PT=100W • Antenna diameter: D=4 (efficiency =0.6) • Location: Bercenay (France) • Latitude = 48º13’07”N • Longitude = 03º53’13”E • Satellite • Receiving antenna gain at boresight: GRmax=40dB • Location: 7ºE (EUTELSAT 1-F2) • Calculate • EIRP of earth station • Free space loss • Received power SatComms A - part 3 - B G Evans

  18. Noise in an Earth Station Noise comes from: Ta= picked up by antenna from outside ( =effective noise) Tf= lossy feeder TLNA, TIPA= amplifiers in receiver chain TD/C= down converter Refer all noise to a reference plane into the LNA G/T Ref rf if Ta DEMOD Tf BASEBAND QoS (BER) IPA LNA TLNA TIPA Lo DOWN CONV TD/L C/NOD Ts SatComms A - part 3 - B G Evans

  19. Noise in a Payload Noise comes from: Antenna received noise –earth + galaxy Feeder lossy noise (nb.290K) Equipment noise –amps / D/C etc. added in same way as for earth station. G/T Ref CD Cu D/C C/Nou eirps SatComms A - part 3 - B G Evans

  20. SatComms A - part 3 - B G Evans

  21. SatComms A - part 3 - B G Evans

  22. Noise Characterisation (1) SatComms A - part 3 - B G Evans

  23. Noise Characterisation (2) SatComms A - part 3 - B G Evans

  24. Noise contribution of an attenuator SatComms A - part 3 - B G Evans

  25. Earth-station system G/Tand noise temp. Ref Ta TLNA Tf D/C TIPA TD/C LdB IPA LNA GLNA GIPA TLNA LD/C SatComms A - part 3 - B G Evans

  26. Earth station antenna noise temperatureExamples (clear sky conditions) SatComms A - part 3 - B G Evans

  27. Exercise (3) - Noise Contribution Budget • Operating frequency = 12 GHz • LNA: TLNA = 150K, GLNA = 50dB • MIXER: TMX = 850K, GMX = -10dB • IF AMP: TIF = 400K, GIF = 30dB • Calculate • Receiver effective input noise temperature TR • Receiver noise figure SatComms A - part 3 - B G Evans

  28. D/C Feeder if IPA LNA Exercise (4) - G/T of C-band earth station • Dish=15m, n=70% • Ta=30K • Tf=290K • Loss f=0.5dB • TLNA=35K • GLNA=30dB • FIPA=3dB • GIPA=20dB • TD/C=1000K • Loss D/C=-10dB • Calculate the earth station G/T • What are the advantages of trading off dish size and LNA temp.? SatComms A - part 3 - B G Evans

  29. Propagation-Effects to be considered- • Radio noise • Ionospheric effects • Absorption • Total electron content effects (group delay, refraction, polarisation rotation) • Scintillation • Tropospheric effects • Attenuation by rain • Depolarisation • Refraction effects • Shadowing and multipath effects SatComms A - part 3 - B G Evans

  30. Clear Sky Noise Temperature • Any ATTENUATION process which involves energy absorption is associated with THERMAL NOISE GENERATION from the medium • Absorption by atmospheric gases is frequency dependent, hence clear sky noise temperature exhibits similar variations with frequency SatComms A - part 3 - B G Evans

  31. Attenuation by atmospheric gases • See CCIR Rep.719 for a detailed description of practical techniques of calculation for LAG. The following curve displays AAG(E) versus frequency; E is the elevation angle. SatComms A - part 3 - B G Evans

  32. Noise temperature of the sun SatComms A - part 3 - B G Evans

  33. Ionospheric effects SatComms A - part 3 - B G Evans

  34. Attenuation due to rain, etc. • Mist • Clouds • Snow • Ice SatComms A - part 3 - B G Evans

  35. SatComms A - part 3 - B G Evans

  36. References for calculation methodology • Course notes or chapter 8 of the book • ITU-R PN 618-3 splant path rain induced attenuation and depolarisation and scintillatin (available from lending libraries or ITU, Geneva) SatComms A - part 3 - B G Evans

  37. Attenuation due to precipitation and cloudsRelevant techniques described in CCIR (see rep.563, 564, 721, 723) SatComms A - part 3 - B G Evans

  38. SatComms A - part 3 - B G Evans

  39. SatComms A - part 3 - B G Evans

  40. Maps of rainfall contours (1/3) Contours of RAINFALL RATE R₀․₀₁(mm/h) exceeded for 0.01% OF AN AVERAGE YEAR: SatComms A - part 3 - B G Evans

  41. Maps of rainfall contours (2/3) Contours of RAINFALL RATE R₀․₀₁(mm/h) exceeded for 0.01% OF AN AVERAGE YEAR: SatComms A - part 3 - B G Evans

  42. Maps of rainfall contours (3/3) Contours of RAINFALL RATE R₀․₀₁(mm/h) exceeded for 0.01% OF AN AVERAGE YEAR: SatComms A - part 3 - B G Evans

  43. Nomogram for determination of specific attenuation  with circular polarization use the arithmetic mean of attenuation with horizontal and vertical polarization SatComms A - part 3 - B G Evans

  44. Typical values of rain attenuation Comments: 30/20 GHz systems face a problem, especially in tropical regions where rainfall rate is very high during small percentage of time. Performance objective must be achieved when rain occurs. The link will probably be over dimensioned during most of the time (margin). SatComms A - part 3 - B G Evans

  45. SatComms A - part 3 - B G Evans

  46. SatComms A - part 3 - B G Evans

  47. SatComms A - part 3 - B G Evans

  48. SatComms A - part 3 - B G Evans

  49. DEPOLARISATION • Rain and ice cause this due to shape of particles • Need to know shape and orientation of particles • Linear and circular POLN different • Circular POLN is worst case • Can form a model linking depolarisation (XPD) and attenuation SatComms A - part 3 - B G Evans

  50. SatComms A - part 3 - B G Evans

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