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Link Budget Calculation

Understand the link budget calculation and parameters between the VINASAT satellite and Earth station at Tam Ky, Quang Nam, including satellite and Earth station specifications, antenna gains, power calculations, uplink and downlink budget calculations.

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Link Budget Calculation

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  1. Link Budget Calculation

  2. Introduction • A satellite communication link is defined as an Earth station - satellite - Earth station connection. • The Earth station - satellite segment is called the uplink. • The satellite - Earth station segment is called the downlink.

  3. Introduction • The Earth station design consists of the Transmission Link Design (Link Budget) and the Transmission System Design. • Link Budget establishes the resources needed for a given service to achieve the performance objectives.

  4. Link Budget Calculation betweenthe VINASAT satellite and the Earth Station at Tam Ky, Quang Nam

  5. LinkParameters * Operation Bandwidth Link design at Ku-Band, using frequency of 14GHz for the uplink and 11GHz for the downlink.

  6. LinkParameters * Earth Station - Located at 15,20N latitude and 108,30E longitude. - The diameter of the antenna (D) is 13m, the aperture efficiency (η) is 65% - Transmission power of Earth Station is 300W. - Earth station antenna height of 7m above sea level.

  7. LinkParameters * Satellite - Located at 1320E longtitude. - EIRPs = 50dBW. - Transponder Bandwidth is 36MHz. - Receiver noise figure F = 4dB. - Receiver figure of merit (G/T)s = 1dB/0K

  8. LinkParameters * Other suppositions - Feeder loss LF = 1dB - Polarization mismatch loss LPOL = 0.5dB - Antenna misalignment loss 0.9dB - Rain loss figure ɣ= 3.96dB/km, rain height hR = 3.208Km - Tropospheric loss figure 0.02dB/Km - Ambient temperature TX = 3000K

  9. Link Budget - Slant range distance is where + Earth station latitudeat Tam Ky= 15.20 N + Ls = 1320E , Le = 108.30N → Difference in longitude between the earth station and the satellite is ΔLe = 1320 – 108.30 = 23,70 → → β0 = 27.920

  10. Link Budget Distance between VINASAT satellite and Earth station at Tam Ky is d=36629.4 km - Elevation angle of satellite from the Earth station θe where Re = 6378 [km] r = 35768 + 6378 = 42146 [km] → tgθe = 1.565 →θe = 57.420

  11. Link Budget • Azimuth of the satellite φa → A = -59.150 → φa = 1800 – (–59.150) = 239.150 - Earth station transmit antenna gain where η= 0.65 ; D = 20m ; fU= 14GHz ; c=3.108m/s → GTe =67.473 [dB]

  12. Uplink Budget - Earth station transmit power (300W) in dB is PTe = 24.77 [dBW] - Equivalent Isotropic Radiated Power of the transmitting Earth station is EIRPe = GTe+ PTe = 92.244 [dBW] - Uplink total loss is LU = LSPU + LFU + LOU

  13. Uplink Budget + Free-space loss is + Rain loss is (LR)U = ɣU.LS [dB] where LS is the effective path length of the signal through the rain At 15,20N latitude, rain height (adapted from CCIR Recommendation 564) is hR = 3+ 0.028 =3,028 [km] hS = 7m = 0,007km ; sinθe = sin57.420

  14. Uplink Budget → Ls = 3.585km ɣU = 3.96dB/km → Uplink rain loss is (LR)U= 14.197dB + Antenna misalignment losses are LTe = 0.9dB ; LRs = 0.9dB +Polarization mismatch loss is LPOL = 0.5dB + Loss due to tropospheric effects is Ltr=0.02 x 15 = 0.3[dB/Km] (assuming troposphere height at Tam Ky is 15km)

  15. Uplink Budget Hence, uplink total loss is LU = LSPU + LFU + LOU = LSPU + LFU + (LRU + LTe + LRs + LPOL + Ltr) = 206.641 + 1 + (14.197 + 0.9 + 0.9 + 0.5 + 0.3) = 224.438 [dB] - Satellite receiver noise temperature với F = 4dB ; T0 = 2900K → TRS = 4380K

  16. Uplink Budget - Uplink noise temperature is TU = TRS + TAS where TRS = 4380K ; TAS = 2900K → TU = 4380 + 2900 = 7280K - Satellite receive antenna gain is GRS= (G/T)S + 10lgTU [dB] where (G/T)S = 1 dB/0K → GRS= 1 + 10lg728 = 29.62 [dB]

  17. Uplink Budget - Satellite received carrier power is CRS = EIRPe – LU + GRS= - 102.574 [dBW] - Uplink noise power is NU = 10lgkTUB where k is Boltzmann’s constant (1,38.10-23 [J/K]) TU equivalent noise temperature (7280K) B is the noise bandwidth of the carrier 36MHz → NU = - 124.4 [dBW] - Uplink carrier-to-noise ratio (C/N)U = - 102.574 + 124.4 = 21.826 [dBW]

  18. Downlink budget - Downlink total loss LD + Free-space loss is (Ltd)D= 20lg(4πfDd) – 20lgc = 20lg(4πx11.109x36629.4x103)-20lg3.108 = 204.55 dB + Downlink rain loss is (LR)D= 14.197dB + Polarization mismatch loss is LPOL= 0.5 dB + Antenna misalignment losses are LTs = 0.9 dB ; LRe = 0.9 dB

  19. Downlink budget → Downlink total loss is LD = (Ltd)D + (LR)D + LPOL+ LTs + LRe = 204.55 + 14.197 + 0.5 + 0.9 + 0.9 = 221.05 dB - Earth station receive antenna gain is where η= 0.65; D = 20m; fD= 11GHz; c=3.108m/s → GRe =65.38 dB

  20. Downlink budget * Downlink noise calculation - Space noise temperature is TS = 52.760K - Rain noise temperature TM Wave attenuation caused by rain is →

  21. Downlink budget - Noise temperature introduced by the loss of the feeder line is - Receiver noise temperature TR ~T1 ,where T1 is noise temperature of the first module of earth station receiver Let’s give TR = 150oK - System noise temperature = 4720K

  22. Downlink budget - System noise power - Downlink carrier-to-noise ratio (C/N)D →

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