Added psk31_sigmodel.m

grc_tests/psk31_sigmodel.m

@@ -0,0 +1,50 @@
+#!/usr/bin/octave
+
+global Tb=20
+
+function g=gbb(t) %impulse response of pulse shaping filter
+	global Tb
+	g=t;
+	for i = 1:size(t)(2)
+		if (t(i)>1*Tb || t(i)<=-1*Tb)
+			g(i) = 0;
+		else
+			g(i) = 0.5+cos((t(i)/(Tb*1))*pi)/2; %this is not RRC, rather a sinusoidal pulse shape
+		end
+	end
+end
+
+function [toreturny, plotrange]=y(s)
+	global Tb
+	slen=size(s)(2)
+	plotrange=(-3*Tb):(slen+2)*Tb-1;
+	plotlen=size(plotrange)(2)
+	toreturny=zeros(1,plotlen);
+	for i=1:slen %sum of (symbol[i] * filter impulse response) for all symbols
+		toreturny+=s(i)*gbb(plotrange.-(i-1)*Tb); 
+	end
+end
+
+function fmtplot(h)
+    FN = findall(h,'-property','FontName');
+    set(FN,'FontName','/usr/share/fonts/truetype/ttf-dejavu/DejaVuSerifCondensed.ttf');
+    set(FN,'FontName','times');
+    FS = findall(h,'-property','FontSize');
+    set(FS,'FontSize',18);
+    set(FS,'FontSize',18);
+end
+
+h=figure(1);
+subplot(2, 1, 1);
+plot(y([1]), 'linewidth', 2)
+title(sprintf("Impulse response of pulse shaping filter\n(1 symbol = %d samples)", Tb))
+xlabel('t [1/Ts]')
+ylabel('h(t)')
+
+subplot(2, 1, 2);
+plot(y([1 1 -1 -1 1 1 1 -1 1 -1 1 1]), 'linewidth', 2)
+title("Baseband signal for modulator input\nbit sequence: 110011101011") %assuming that differential encoding has already been performed
+xlabel('t [1/Ts]')
+ylabel('s(t)')
+fmtplot(h);
+pause