3D surface plot from for loop

Hi all,

The following is my code, which calculates RF path loss between a satellite and a ground station, factoring in altitude and trajectory.

 % code
f=5*10^6; %must be *10^3 less than given f. For example if f=5GHz, use 5MHz
h=700;
Gt=0;
Gr=0;
Nf=-100;
for i = 1:181   
    ang(i)=i-1
    d(i)=sqrt(((6371+h)^2)-(6371^2)*(cos(ang(i)*(pi/180)).^2))-6371*sin(ang(i)*(pi/180));
    Lp(i)=20*log10((4*pi()*d(i)*f)/(300000));
    Pt=10*log10(57.27*0.193)+30; %convert to dbm
    Pr(i)=Pt+Gt+Gr-Lp(i);
    SNR(i)=Pr(i)-Nf
end

I can easily create 2D plots from this such as plot(ang,Lp) etc.. But I want to create a 3D plot using the surf command, which plots (ang,Lp,d).

How is this possible ?

Thanks in advance.

[John BG]

there are satellite comms examples readily available at the MATLAB file exchange.

For instance

available from

https://uk.mathworks.com/help/comm/examples/rf-satellite-link.html?s_tid=srchtitle

the channel is already modelled in some of the blocks.

John BG

<mailto:[e-mail] [e-mail]>

Answer 1

[Massimo Zanetti]

Most probably you don't want to plot a surface, instead a plot of a line in a 3D space. Try this:

plot3(ang,Lp,d); grid on;

Is that what you need?

[MATLABmet]

Hi Massimo,

That looks more like what I want. However, I now want to bring the h value into the loop and make it range from 700:800Km. So really I need a 3 dimensional plot that represents distance, angle, and pathloss.

thanks again,

[Massimo Zanetti]

Ok, so what you need is more likely a family of curves. Consider that there is no need of any loop, thanks to Matlab implicit expansion. See here:

f=5*10^6; %must be *10^3 less than given f. For example if f=5GHz, use 5MHz
Gt=0;
Gr=0;
Nf=-100;

h = (700:5:800)';
ang = 0:180;
d = sqrt(((6371+h).^2)-(6371^2)*(cos(ang*(pi/180)).^2))-6371*sin(ang*(pi/180));
Lp = 20*log10((4*pi*d*f)/(300000));
Pt = 10*log10(57.27*0.193)+30; %convert to dbm
Pr = Pt+Gt+Gr-Lp;
SNR =Pr-Nf;

plot3(ang,Lp,d); grid on;

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