112 lines
2.2 KiB
Matlab
112 lines
2.2 KiB
Matlab
## Copyright (C) 2016 Valentin Gehrke
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##
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## This program is free software; you can redistribute it and/or modify it
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## under the terms of the GNU General Public License as published by
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## the Free Software Foundation; either version 3 of the License, or
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## (at your option) any later version.
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##
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## This program is distributed in the hope that it will be useful,
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## but WITHOUT ANY WARRANTY; without even the implied warranty of
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## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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## GNU General Public License for more details.
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##
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## You should have received a copy of the GNU General Public License
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## along with this program. If not, see <http://www.gnu.org/licenses/>.
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## -*- texinfo -*-
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## @deftypefn {Function File} {@var{retval} =} phasenmodulation (@var{input1}, @var{input2})
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##
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## @seealso{}
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## @end deftypefn
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## Author: Valentin Gehrke <s7745593@e03101>
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## Created: 2016-07-28
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datalen = 20;
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pilot = [ 1 0 1 0 ];
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dr = rand(1,datalen) > 0.5;
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signallen = datalen + size(pilot,2);
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d = [ pilot dr ];
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n = 0:signallen-1;
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phases = [ -pi/2 pi/2 ];
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Tb = 0.1;
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fc = 100;
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fa = 1000;
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subplot(6,1,1)
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stem(n,d)
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timelen = (signallen*Tb - 1/fa);
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t = 0:(1/fa):timelen;
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phi = phases( d( floor(t/Tb) + 1) + 1);
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subplot(6,1,2)
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plot(t,phi)
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axis([0 timelen -pi pi])
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s = cos(2*pi*fc*t + phi);
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[bs,as] = butter(5,2*1.5*fc/fa);
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slow = filter(bs,as,s);
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subplot(6,1,3);
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plot(t,slow);
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axis([0 timelen -1.5 1.5])
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noise = 1 * randn(size(slow));
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sn = slow + noise;
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subplot(6,1,4);
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[bbp,abp] = butter(5,[2*0.5*fc/fa , 2*1.5*fc/fa]);
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sbp = filter(bbp,abp,sn);
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plot(t,sn);
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axis([0 timelen -3 3])
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sr = sbp .* cos(2*pi*fc*t);
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si = sbp .* sin(2*pi*fc*t);
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[b,a] = butter(5,2*0.7*fc/fa);
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srlow = filter(b,a,sr);
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silow = filter(b,a,si);
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cmplxs = srlow + j*silow;
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phase = angle(cmplxs);
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m = zeros(size(phase));
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for i = 1:size(t,2)
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[tmp, idx] = min(abs(phase(i) - phases));
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m(i) = idx-1;
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endfor
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subplot(6,1,5);
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plot(t,phase,t,phases(m+1));
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axis([0 timelen -pi pi])
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ds = zeros(1,signallen);
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for i = 1:signallen;
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ts = (i-1) * Tb;
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te = i * Tb;
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q = t > ts & t < te;
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ds(i) = mean(m(q)) > 0.5;
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endfor
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subplot(6,1,6)
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err = (ds != d);
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cla
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stem(n(~err),ds(~err))
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hold on;
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stem(n(err),ds(err),'rx')
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hold off;
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