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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} =} garage (@var{input1}, @var{input2})
+##
+## @seealso{}
+## @end deftypefn
+
+## Author: Jens Ahrensfeld <ahrensfeld@w2ess001vm>
+## Created: 2018-12-06
+
+function [bits, x] = garage_ip (numSamplesPerSym)
+
+k_n = 0.00;	% NOise
+k_s = 1.0;		% Sym
+
+baud_init = 9600;
+fs = baud_init * numSamplesPerSym;
+
+numSyms = 100;
+numBursts = 3;
+numSymsPauseBetweenBurst = 50;
+
+syms = rand(numSyms, 1) > 0.5;
+
+bit = 0;
+% Line coding
+syms_m = manchester(syms);
+
+% Upconvert
+x = [];
+
+for k=1:numBursts
+	for n=1:2*numSyms,
+		for m=1:numSamplesPerSym,
+			x = [x syms_m(n)];
+		end
+	end
+	x = [x zeros(1, numSymsPauseBetweenBurst*numSamplesPerSym)];
+end
+
+% Channel
+[b,a] = butter(2, numSamplesPerSym/4*baud_init/fs);
+y = resample (x, 131, 121);
+%y = x;
+y = k_s*filter(b, a, y) + k_n*randn(1, length(y));
+
+N = length(y);
+
+baud = baud_init;
+bit = 0;
+
+% The master clock counter
+countReload = numSamplesPerSym-1;
+count = countReload;
+smp = [];
+smp_n = [];
+bits = [];
+
+v_min = 0;					% Threshold max
+v_max = 0;					% Threshold min
+hyst_thr = 0.5;				% Threshold hysteresis
+rho_thr = 1e-5;				% Threshold forgetting factor
+alpha_lead = 0.016;			% Symbol syncronizer loop filter lead 
+alpha_lag = 0.000008;		% Symbol syncronizer loop filter lag 
+lag_accu = 1;				% Symbol syncronizer loop filter
+ns = 1;						% Start sample source
+n = 1;						% Start sample sink
+err = 0;					% Error
+while ns < N
+	% Get next interpolated sample
+	is = fix(ns);
+	mu = ns - is;
+	ys = (1-mu).*y(is) + mu.*y(is+1);
+
+	% Calculate threshold
+	v_thr = (v_max - v_min) / 2;
+	if ys < v_min
+		v_min = ys;
+	elseif ys > v_max
+		v_max = ys;
+	end
+	v_min = v_min + rho_thr*(v_thr - v_min);
+	v_max = v_max - rho_thr*v_max;
+
+	% Detect bit change
+	bitChg = 0;
+	if (bit == 1)
+		if ys < (hyst_thr*v_thr)
+			bit = 0;
+			bitChg = 1;
+		end
+	else
+		if ys > (hyst_thr*v_thr)
+			bit = 1;
+			bitChg = 1;
+		end
+	end
+	
+	% Calc error
+	if (bitChg)
+		err = -(count - fix(numSamplesPerSym/2));
+	end
+	
+	% Sample bit at baud rate = fs/numSamplesPerSym
+	if count == 0
+		smp = [smp ys];
+		smp_n = [smp_n n];
+		bits = [bits bit];
+	end;
+	if count > 0
+		count = count - 1;
+	else
+		count = countReload;
+	end
+	vcorr = alpha_lead*err + lag_accu;
+	lag_accu = lag_accu + alpha_lag*err;
+	baud = vcorr*fs/numSamplesPerSym;
+	_err(n) = err;
+	_baud(n) = baud;
+	_cnt(n) = vcorr;
+	_v_tr(n) = v_thr;
+	_ys(n) = ys;
+	n = n + 1;
+	ns = ns + vcorr;
+end
+bits = bits';
+
+n = 1:length(_ys);
+
+% Plot
+subplot(3, 1, 1)
+plot(n, _ys, smp_n, smp, 'ro', n, _v_tr, 'y'); grid;
+subplot(3, 1, 2)
+plot(n, _err); grid;
+subplot(3, 1, 3)
+plot(n, _baud); grid;
+
+endfunction