mSatComLinkBudget.m

% A satellite at a distance of of 40,000 km from a point on the earth's
%surface radiates a power 10 W from an antenna with a gain of 17 dB in the 
% direction of the observer. Find the flux density at the receiving point and the power
% received by the antenna at this point with an effective area of 10 m^2

%% Parameters (Example 4.2.1)
Pt=10; %transmitted power in watts
Gt=50; %Gain of the antenna with an effective area collecting area of 10 m^2
Gr=52.3; %Gain of the receiving antenna
R=40000e3; %distance from a point on the earth's surface
Ae=10; %Effective Area in meters^2
c=2.99e8; %speed of light
f=11e9; %operational frequency

%% Power flux density
F=(Pt*Gt)/(4*pi*(4e7)^2); 
EIRP=10*log10(Pt*Gt); 

%% Power Received
Pr=F/Ae; % Power received at the antenna 

%% Calculations in dB
FdB=10*log10(Pt*Gt)-20*log10(R)-10*log10(4*pi); %Power Flux Density in dB
PrdB=FdB+10; % Power received at the antenna in dB

%% Alternate method (Example 4.2.2)
lambda=c/f;
pathL=20*log10((4*pi*R)/lambda); %Path Loss from satellite to antenna
Pr2=EIRP+Gr-pathL; %Power received by the Earth Station in dB