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git-svn-id: http://moon:8086/svn/matlab/trunk@100 801c6759-fa7c-4059-a304-17956f83a07c
2018-12-14 17:16:15 +00:00
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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} =} im_eval (@var{input1}, @var{input2})
+##
+## @seealso{}
+## @end deftypefn
+
+## Author: Jens Ahrensfeld <ahrensfeld@w2ess001vm>
+## Created: 2018-10-22
+
+function s = im_eval ()
+
+s1 = sig_gen('lo', 'sine', [0 500], [0.0 1]);
+s2 = sig_gen('s1', 'sine', [0 100 500 900 1400], [0.0 0.5 1.0 0.5 0.25]);
+
+s = modulate(s1, s2);
+
+close all;
+plotSig(s);
+function s = sig_gen(name, type, freq, amp)
+
+peaks = [];
+switch type
+	case 'sine'
+		f = freq;
+		a = amp;
+	case 'rect'
+		N = 10;
+		f = [];
+		a = [];
+		k = 1;
+		for n=1:N
+			f = [f k*freq];
+			a = [a amp/k];
+			k = k + 2;
+		end
+endswitch
+	
+s = struct('name', name, 'f', f, 'a', a);
+endfunction
+
+function m = modulate(s1, s2)
+
+m = struct('name', sprintf("%s x %s", s1.name, s2.name), 'f', [], 'a', []);
+
+f = [];
+a = [];
+
+for i=1:length(s1.f)
+	for j=1:length(s2.f)
+		f1 = s1.f(i) - s2.f(j);
+		f2 = s1.f(i) + s2.f(j);
+		a = s1.a(i) * s2.a(j);
+		
+		m = addFreq(m, f1, a);
+		m = addFreq(m, f2, a);
+	end
+end
+
+endfunction
+
+function x = addFreq(x, f, a)
+
+found = 0;
+for i=1: length(x.f)
+	if (x.f(i) == f)
+		found = i;
+		break;
+	end
+end
+if (found > 0)
+	x.a(found) = x.a(found) + a;
+elseif a ~= 0
+	x.f = [x.f f];
+	x.a = [x.a a];
+end
+
+endfunction
+
+function plotSig(s)
+	stem(s.f, s.a, 'baseline', -10); grid; legend(s.name)
+endfunction
+	
+endfunction