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git-svn-id: http://moon:8086/svn/matlab/trunk@100 801c6759-fa7c-4059-a304-17956f83a07c

qdemod_eval.m

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+## Copyright (C) 2018 Jens Ahrensfeld
+## 
+## This program is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or
+## (at your option) any later version.
+## 
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+## 
+## You should have received a copy of the GNU General Public License
+## along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*- 
+## @deftypefn {Function File} {@var{retval} =} qdemod_eval (@var{input1}, @var{input2})
+##
+## @seealso{}
+## @end deftypefn
+
+## Author: Jens Ahrensfeld <ahrensfeld@w2ess001vm>
+## Created: 2018-11-16
+
+function qdemod_eval
+
+fa = 1000;
+T = 1/fa;
+N = 1000
+
+t = (0:N-1)*T;
+
+omega_x_0 = 100.0;
+omega_x_1 = 200.0;
+phi_x = pi/8*0;
+
+omega_lo = 150.0;
+
+
+lo_r = cos(2*pi*omega_lo*t);
+lo_i = sin(2*pi*omega_lo*t);
+
+x = cos(2*pi*omega_x_0*t + phi_x) + cos(2*pi*omega_x_1*t + phi_x);
+y = x.*lo_r + x.*lo_i*i;
+
+subplot(2,1,1);
+plot(t, y, t, x); grid;
+subplot(2,1,2);
+Y = fftshift(fft(y, N))/N;
+X = fftshift(fft(x, N))/N;
+f = (-length(X)/2:length(X)/2-1)/N*fa;
+plot(f, abs(X), f, abs(Y)); grid;
+
+endfunction