jens
5cd7c299e4
git-svn-id: http://moon:8086/svn/matlab/trunk@151 801c6759-fa7c-4059-a304-17956f83a07c
112 lines
2.6 KiB
Objective-C
112 lines
2.6 KiB
Objective-C
## Copyright (C) 2021 Jens
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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, but
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## 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
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## <https://www.gnu.org/licenses/>.
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## -*- texinfo -*-
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## @deftypefn {} {@var{retval} =} iridium (@var{input1}, @var{input2})
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##
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## @seealso{}
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## @end deftypefn
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## Author: Jens <jens@orion>
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## Created: 2021-01-16
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function iridium (name)
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[x, fs] = audioread(name);
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xc = (x(:,1) + i*x(:,2))';
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close all;
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N = length(x);
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phi = angle(xc);
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phi_uw = phi_unwrap(phi);
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dphi = [0 diff(phi_uw)];
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[lo] = losc(dphi);
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xc_cfo = xc .* lo;
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#xc_cfo = xc_cfo .* conj(xc_cfo);
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phi_cfo_uw = phi_unwrap(angle(xc_cfo));
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dphi_cfo = [0 diff(phi_cfo_uw)];
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foff = dphi_cfo*48000;
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found = find_preamble(dphi_cfo)
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alpha_mean = 0.1;
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dphi_mean = filter([0 alpha_mean], [1 -(1-alpha_mean)], dphi_cfo);
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#plot(1:N, abs(xc), 1:N, atan(xc)); grid;
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#plot(1:N, dphi, 1:N, phi_uw, 1:N, real(lo)); grid;
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subplot(3,1,1)
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#plot(1:N, dphi, 1:N, dphi_cfo); legend('dphi','dphi_{cfo}'); grid;
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plot(1:N, real(xc_cfo), 1:N, imag(xc_cfo)); legend('xc_cfo_{re}','xc_cfo_{im}'); grid;
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subplot(3,1,2)
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plot(1:N, phi_cfo_uw, "-o"); legend('phi'); grid;
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subplot(3,1,3)
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plot(1:N, dphi_cfo, "-o", 1:N, dphi_mean, 'r-'); legend('dphi'); grid;
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start=found(1)
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ende=start + 128
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step=2
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figure
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plot(real(xc_cfo(start:step:ende)), imag(xc_cfo(start:step:ende)), 'x'); grid;
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function found = find_preamble(phi)
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thr = 0.5;
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nsmp = 16;
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last = phi(1);
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count = 0;
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found = [];
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for n=1:length(phi)
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count = count + 1;
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if abs(phi(n) - last) > thr;
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count = 0;
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endif
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if count == nsmp
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found = [found n - nsmp];
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endif
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last = phi(n);
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endfor
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endfunction
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function [res] = losc(dphi)
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alpha_sm = 0.995;
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dphi_sm = dphi(1);
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phi = 0;
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for n=1:length(dphi)
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res(n) = exp(-j*phi);
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phi = phi + dphi_sm;
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dphi_sm = (1-alpha_sm)*dphi_sm + alpha_sm*dphi(n);
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endfor
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endfunction
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function res = phi_unwrap(phi)
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offset = 0;
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last = phi(1);
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for n=1:length(phi)
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if (phi(n) - last) > pi
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offset = offset - 2*pi;
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end
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if (phi(n) - last) < -pi
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offset = offset + 2*pi;
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end
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res(n) = phi(n) + offset;
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last = phi(n);
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endfor
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endfunction
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endfunction
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