%
% Carrier to noise ratio computation
% for a satellite receiver.
% Assumes loses between satellite transmitter and its
% antenna are negligible
%


% Transmitter carrier frequency in Megahertz 
f = 4e3;
% The minimum transmitter power in watts;
Ptmin = 10;
% The maximum transmitter power in watts;
Ptmax = 50;
% The transmitter antenna gain in dBi  ');
Gt = 40;
% The receiver antenna gain in dBi  ');
Gr = 30;
% Path length in km
d = 4e4;
% receiver bandwidth in hertz
B = 1e6; 
% figure of merit for receiving system in dB
G_T = 21;


%
% Compute the overall loss in dB
% 
%
fsl = 32.44+20*log10(d)+20*log10(f);



Ptstep = (Ptmax-Ptmin)/100;

Pt = Ptmin:Ptstep:Ptmax;

% Transmitter power in dbW

Ptw = 10*log10(Pt);
% Effective isotropic radiated power in dBW
EIRP = Ptw + Gt;
%
% Boltzmann constant expressed in dBW
kdbW = -228.6;

%
% Compute carrier-to-noise ratio in dB
%

C_N = EIRP - fsl + G_T - kdbW - (10*log10(B))

%
% Plot carrier-to-noise ratio over the transmitter power range
%
clf
figure(1)

plot(Pt,C_N);
title('Carrier-to-noise ratio over the transmitter power range')
ylabel('Carrier-to-noise ratio in dB')
xlabel('transmitter power in watts')
grid
%