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Link Power Budgetting

4.Calculation of uplink to noise ratio

1.Up link rain attenuation (dB)   Rain fall results in attenuation of radio waves by scattering , and by absorption , of energy from the wave. Rain attenuation increases with increasing frequency and in worse at Ku band compared to C band. Studies have shown that the rain attenuation for horizontal polarization is considerably greater than for vertical polarization.

2.Satellite G/T (dB/k)   G/T ratio indicates figure of merit. G/T ratio is the ratio of gain of the satellite to the thermal noise temperature of the satellite. G/T ratio depends on the satellite components. 

3.Uplink C/No(dB Hz)   The up link of a satellite circuit is the link in which the earth station is transmitting the signal and the satellite is receiving it .
Carrier to noise ratio of up link is given as

                            [C/No]U = [EIRP]U + [G/T]U -[losses] U + 228.6
                                          =Transmitter EIRP- (Up link path losses + Up link rain attenuation) + Satellite G/T + 228.6 (dB)..[6]

Example : calculate power rating of ground transmitter operating at following conditions Transmitter EIRP37.97 dB W, Up link rain attenuation-0.0 dB, Up link path loss 199.62 dB, satellite G/T(dB/K)-5.00
                          [C/No]U = 37.97 5.00-199.92+228.6
                                          = 61.65 dB

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