MLDesign Technologies, Inc.

Mainnavigation

Subnavigation

BORDER

 
 
 

Pagecontent

Calculation of a SatCom Doppler Frequency

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

Figure 1: Doppler analysis output
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);
  12. addEpoch('Teledesic',2002,3,26,12,0,0);
  13.  
  14. % Epoch group of satellite
  15. addSatellite('S1a',7728,0,90,9,0,0,'Teledesic');
  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
  27. addStation('E1',I_earth,45,g(1)+7.5,g(2),0);
  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]')