Link analysis for an earth orbiting spacecraft.
Includes noise analysis. Computes the link with and without rain. -------------------------------------------------------------------------
Reference: Maral, G. and M. Bousquet. (1998.) Satellite Communications
Systems, Third Edition. John Wiley.
-------------------------------------------------------------------------
See also DBSignal, AntennaGain, Beamwidth3dB, Gain3dB,
LossAtmosphericGas, LossDepointing, LossFreeSpace, LossPrecipitation,
TAntennaGround, TAttenuator, TReceiver, TSky
-------------------------------------------------------------------------Contents
%-------------------------------------------------------------------------- % Copyright (c) 2001 Princeton Satellite Systems, Inc. % All rights reserved. %-------------------------------------------------------------------------- %--------------------------------------------------------------------------
2.5.8 and 2.5.9 Example 1 and 2 pp. 42-46.
%--------------------------------------------------------------------------
Spacecraft
%----------- % diameter of transmit antenna (m) dT = 4; % transmit frequency (GHz) fD = 12; % transmitted power (dBW) pT = DBSignal(10); % loss between the amplifier on the satellite and the antenna (dB) lFTX = 1; % Depointing angle (deg) thetaT = 0.1; % 3 dB Angle (deg) theta3DB = 2; % efficiency effT = 0.55; % distance for free space loss (km) r = 40000; % Elevation angle (deg) E = 10; % link attenuation due to the atmosphere (dB) lA = LossAtmosphericGas( fD, E ); % Illumination factor (deg) fIllumination = 70; % loss being at the 3dB edge of the beam contour (dB) lEdge = 3;
EIRP Satellite - Effective Isotropic Radiated Power
%----------------------------------------------------
gT = Gain3dB( theta3DB, fIllumination, effT );
eIRPSL = pT + gT - lEdge - lFTX;
Downlink attenuation
%---------------------
lFS = LossFreeSpace( fD, r );
lD = lA + lFS;
Ground station
%--------------- f = 1; % loss between the feed and the antenna (dB) lFRX = 0.5; % temperature of the feed tF = 290; % diameter of the receiving antenna (m) dR = 4; % receiver efficiency effR = 0.6; % ambient temperature of the ground tGround = 45;
Downlink system noise temperature
%---------------------------------- tSky = TSky( 12, 10 ); tA = TAntennaGround( tSky, 0, tGround ); tERX = TAttenuator( tF, f ); % downlink system noise temperature (K) tD = TReceiver( tA, lFRX, tF, tERX ); gR = AntennaGain(struct('type','circular aperture','area',pi*dT^2/4,'eff',effR),fD);
Pointing loss
%-------------- theta3DB = Beamwidth3dB( dR, fD, fIllumination ); lP = LossDepointing( thetaT, theta3DB ); gOverT = gR - lP - lFRX - DBSignal(tD); cOverN0 = eIRPSL - lD + gOverT - DBSignal(1.381e-23); fprintf('\n\n2.5.8 Example 1 and 2.5.9 Example 2: Downlink\n-------------------------------------------\n') fprintf('Gain Transmit Antenna = %10.2f (dBW)\n',gT); fprintf('Transmitter Loss = %10.2f (dB)\n',lFTX); fprintf('Theta 3 dB = %10.2f (dB)\n',theta3DB); fprintf('EIRP SL = %10.2f (dBW)\n',eIRPSL); fprintf('Free Space Loss = %10.2f (dB)\n',lFS); fprintf('Atmospheric Loss = %10.2f (dB)\n',lA); fprintf('Downward Path Loss = %10.2f (dB)\n',lD); fprintf('Gain Receive Antenna = %10.2f (dB)\n',gR); fprintf('Receiver Loss = %10.2f (dB)\n',lFRX); fprintf('Noise Temperature Receiver = %10.2f (deg-K)\n',tERX); fprintf('Pointing Loss = %10.2f (dB)\n',lP); disp('---- Clear Sky ----') fprintf('Noise Temperature Ground Antenna = %10.2f (deg-K)\n',tA); fprintf('Noise Temperature Downlink = %10.2f (deg-K)\n',tD); fprintf('(G/T)ES Clear Sky = %10.2f (dB)\n',gOverT); fprintf('C/N0 Clear Sky = %10.2f (dB)\n',cOverN0);
2.5.8 Example 1 and 2.5.9 Example 2: Downlink ------------------------------------------- Gain Transmit Antenna = 38.23 (dBW) Transmitter Loss = 1.00 (dB) Theta 3 dB = 0.44 (dB) EIRP SL = 44.23 (dBW) Free Space Loss = 206.07 (dB) Atmospheric Loss = 0.29 (dB) Downward Path Loss = 206.36 (dB) Gain Receive Antenna = 51.81 (dB) Receiver Loss = 0.50 (dB) Noise Temperature Receiver = 75.09 (deg-K) Pointing Loss = 0.63 (dB) ---- Clear Sky ---- Noise Temperature Ground Antenna = 65.02 (deg-K) Noise Temperature Downlink = 164.57 (deg-K) (G/T)ES Clear Sky = 28.52 (dB) C/N0 Clear Sky = 94.99 (dB)
With rain
%---------- disp('---- Rain ----') lRain = LossPrecipitation( fD, 'e', 0.01, 45, 0, 0, [40000;0;0], 0 ); tA = TAntennaGround( tSky, lRain, tGround ); tD = TReceiver( tA, lFRX, tF, tERX ); lD = lA + lFS + lRain; gOverT = gR - lP - lFRX - DBSignal(tD); cOverN0 = eIRPSL - lD + gOverT - DBSignal(1.381e-23); fprintf('Rain Loss = %10.2f (dB)\n',lRain); fprintf('Downward Path Loss = %10.2f (dB)\n',lD); fprintf('Noise Temperature Ground Antenna = %10.2f (deg-K)\n',tA); fprintf('Noise Temperature Downlink = %10.2f (deg-K)\n',tD); fprintf('(G/T)ES = %10.2f (dB)\n',gOverT); fprintf('C/N0 = %10.2f (dB)\n',cOverN0); %--------------------------------------
---- Rain ---- Rain Loss = 3.63 (dB) Downward Path Loss = 209.99 (dB) Noise Temperature Ground Antenna = 209.44 (deg-K) Noise Temperature Downlink = 293.29 (deg-K) (G/T)ES = 26.01 (dB) C/N0 = 88.85 (dB)