function p=convertparosfreqpress( Dc, F, T );
% CONVERTPAROSFREQPRESS - Converts ext paros freq to  pressure
% p=convertparosfreqpress( Dc, F, T );
%
% Input:  Dc - Structure w/ conversion coefficients
%              (see loaddruckcalfile.m)
%         F  - Array of frequencies to convert (note that these
%              are 0.001*(1e6*PressFreqOffset*+LextPress), where
%              LextPress is the value recorded on the ADV. Valid
%              LextPress numbers are in the range of 35000 KHz, and
%              valid PressFreqOffset numbers are normally around 21, but
%              should sometimes be higher to prevent overflow as they
%              are stored by the logger.
%         T  - Temperature (scalar value) [deg C]
%
% Output: p -  Array of pressures [decibars]
%
% Based on Sontek advdata.c, Version 7.71
% with corrections for T calibration files.

% Chris Sherwood, USGS
% Last revised August 18, 2003

[m,n]=size(F);
if(m==1 & n>1), F=F'; end
nf = max(m,n);

Psi_To_mbar=68.947573;

% Infer temperature period from temperature
% (invert quadratic equation used to calc temp from temp freq by
% Paros)
if( Dc.Y(3)~=0 ),error('This only works when Dc.Y(3) is zero'),end
if(Dc.Y(2)~=0),
  u  = ones(nf,1)*(-Dc.Y(1)-sqrt(Dc.Y(1)*Dc.Y(1)+4*T*Dc.Y(2))) ./ (2*Dc.Y(2));
else
  u = T;
  fprintf(1,'No Y coefficients.\n')
end
u2 = u .* u;
%/* Pressure period in microsec  */
tau = 1.0e6 ./ F;
c  = Dc.C(1) + Dc.C(2) * u + Dc.C(3) * u2;
d  = Dc.D(1) + Dc.D(2) * u;
t0 = Dc.T(1) + Dc.T(2) * u + Dc.T(3) * u2 ...
     + Dc.T(4) * u .* u2 + Dc.T(5) * u2 .* u2;

delta = (t0 ./ tau);
delta = (1 - delta .* delta);
p = 0.01*Psi_To_mbar*( c.*delta.*(1-d.*delta) );