time   calls  line
                  1 function d = calibrate_linearity(d)
                  2 % d = calibrate_linearity(d)
                  3 %
                  4 % This function uses the measured detector diode curves to correct for the
                  5 % non-linearity of the detector diodes.
                  6 %
                  7 % To look at the linearity of the data --> convert switchData to Volts then
                  8 % into power using the measured diode response. Then convert back to
                  9 % digital units, because some functions (namely passband functions) expect
                 10 % units in digital units.
                 11 %
                 12 % OGK and ACT, July 2011
                 13 %
                 14 
                 15 
                 16 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
                 17 % Diode curves as measured by Oliver
                 18 % Best fit quadratics:
                 19 %
                 20 % Input power (mW) = D(1).*x^2 + D(2)*x + D(3)  
                 21 %
                 22 %  where x is ouput voltage in V
                 23 %
                 24 %  D is the array of polynomial coefficaient D[12,1:3]
                 25 %  For diodes 1 to 12  with 3 coefficients each
                 26 %
                 27 %%%%%%%%%%%%%%%%%%%%%%%%%%
                 28 
             1   29 D(1,1:3) = [ 18.480 1.285 0.000]; 
             1   30 D(2,1:3) = [ 17.395 1.244 0.000]; 
             1   31 D(3,1:3) = [ 17.954 1.252 0.000]; 
             1   32 D(4,1:3) = [ 17.501 1.251 0.000]; 
             1   33 D(5,1:3) = [ 19.851 1.391 0.000]; 
             1   34 D(6,1:3) = [ 17.264 1.236 0.000]; 
             1   35 D(7,1:3) = [ 18.786 1.309 0.000]; 
             1   36 D(8,1:3) = [ 17.384 1.251 0.000]; 
             1   37 D(9,1:3) = [ 18.208 1.266 0.000]; 
             1   38 D(10,1:3) = [ 17.357 1.211 0.000]; 
             1   39 D(11,1:3) = [ 17.444 1.217 0.000]; 
             1   40 D(12,1:3) = [ 16.289 1.258 0.000]; 
                 41 
                 42 % The average diode has linear slope, used to convert the non-linearity
                 43 % corrected power back to a voltage.
                 44 % See wiki page http://astrowiki.physics.ox.ac.uk/CBass/DetectorDiode
             1   45 V2mW = 1.289; % mW/V 
                 46 
                 47 % Convert switchData from Backend units to Volts
                 48 % To account of the gain of readout and filter board we have a factor of
                 49 % 6.5 in the equation, which is the gain of the backend board.
                 50 % 4999 digital units corresponds to an input voltage of +1.25V
                 51 % Therefore the conversion factor is:
             1   52 BU2V = 1.25./((10^4)/2)/6.5; % V/DU 
                 53 
  0.10       1   54 d.antenna0.receiver.switchData = d.antenna0.receiver.switchData*BU2V; 
                 55 
                 56 % Now use diode calibration curves to go from V to mW input power
                 57 % Diodes are in pairs for the 24 channels
                 58 % Preallocate power array
  0.09       1   59 P = ones(size(d.antenna0.receiver.switchData)); 
                 60 
             1   61 for i=1:12 
                 62     %first channel with this diode
  0.04      12   63     V = d.antenna0.receiver.switchData(:,(2*i)-1); 
  0.08      12   64     P(:,(2*i)-1) = ( (D(i,1)*V.^2) + (D(i,2)*V) + D(i,3) ); 
  0.01      12   65     clear V 
                 66     % second channel with this diode
  0.04      12   67     V = d.antenna0.receiver.switchData(:,(2*i)); 
  0.08      12   68     P(:,(2*i)) = ( (D(i,1)*V.^2) + (D(i,2)*V) + D(i,3)); 
  0.01      12   69     clear V 
            12   70 end 
                 71 
                 72 % go back to digital units
  0.27       1   73 P = P/V2mW/BU2V; 
             1   74 d.antenna0.receiver.switchData = P; 
                 75 
  0.01       1   76 clear P 
                 77 
             1   78 end