Calculation of a SatCom Doppler Frequency

The plot below shows the analysis of the Doppler frequency for a satellite passing overhead.

Script - Doppler frequency of satellite
1. % Demo: Doppler frequency of satellite
2. %
3. % This demo sets up a satellite passing overhead and
4. % computes and displays the doppler frequency
5. %
6.
7. removeAll;
8. setSimEpoch(2002,3,26,12,0,0);
9.
10. % Start time for simulation
11. setSimStepSize(1);
13.
14. % Epoch group of satellite
16.
17. % Define satellite
18. setSimTime(0)
19.
20. % Initialize simulation
21. g = GeoPosition(3);
22.
23. % Get geographic position of satellite
24. g(1:2) = g(1:2)*r2d;
25.
26. % Convert from radians to degrees
28.
29. % Add station 7.5 deg north of satellite
30. t = 0:1:600;
31.
32. % Define simulation time vector
33. rvec=zeros(size(t));
34.
35. % Initialize vector of relative velocities
36. j = 0;
37. for i = t,
38.     j = j+1;
39.     stepSim;
40.
41.     % Advance simulation by 1 sec
42.     [d,r,a,e,v] = RelPosition('E1');   % Get distance, rel velocity, ...
43.     rvec(j) = r(2);                    % Store rel velocity in array
44. endfor
45.
46. erase
47.
48. window('111');
49. plot(t,rvec*19.3e9/cLight, 'grid');
50.
51. % plot rel velocity, converted to doppler f
52. title('Doppler Frequency: h=1450km, f=19.3GHz')
53. ylabel('df (Hz)',
54.        'Fl s ls');
55. xlabel('t [sec]')