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function moddemo(action,s,ss);
%MODDEMO Demonstrates modulation and demodulation.
%
% See also CZTDEMO, FILTDEMO, SOSDEMO.
% Copyright (c) 1988-98 by The MathWorks, Inc.
% $Revision: 1.1 $ $Date: 1998/05/20 14:57:14 $
% Possible actions:
% initialize
% window
% lowpass
% operation
% cutoff
% order
% button callbacks:
% radio
% apply
% info
% close
if nargin<1,
action='initialize';
end;
if strcmp(action,'initialize'),
shh = get(0,'ShowHiddenHandles');
set(0,'ShowHiddenHandles','on')
figNumber=figure( ...
'Name','Modulation/Demodulation Demo', ...
'handlevisibility','callback',...
'IntegerHandle','off',...
'NumberTitle','off');
%==================================
% Set up the axes
origHndl = axes( ...
'Units','normalized', ...
'Position',[0.10 0.80 0.60 0.18], ...
'XTick',[],'YTick',[], ...
'Box','on');
modHndl = axes( ...
'Units','normalized', ...
'Position',[0.10 0.3 0.60 0.45], ...
'XTick',[],'YTick',[], ...
'Box','on');
demodHndl = axes( ...
'Units','normalized', ...
'Position',[0.10 0.07 .60 0.18], ...
'XTick',[],'YTick',[], ...
'Box','on');
%====================================
% Information for all buttons (and menus)
labelColor=[0.8 0.8 0.8];
yInitPos=0.90;
menutop=0.95;
btnTop = 0.6;
top=0.75;
left=0.785;
btnWid=0.175;
btnHt=0.06;
textHeight = 0.05;
textWidth = 0.12;
% Spacing between the button and the next command's label
spacing=0.012;
%====================================
% The CONSOLE frame
frmBorder=0.019; frmBottom=0.04;
frmHeight = 0.92; frmWidth = btnWid;
yPos=frmBottom-frmBorder;
frmPos=[left-frmBorder yPos frmWidth+2*frmBorder frmHeight+2*frmBorder];
h=uicontrol( ...
'Style','frame', ...
'Units','normalized', ...
'Position',frmPos, ...
'BackgroundColor',[0.5 0.5 0.5]);
%====================================
% The DISPLAY Menu
menuNumber=1;
yPos=menutop-(menuNumber-1)*(btnHt+spacing);
if ~isstudent
labelStr='time|psd|specgram';
else
labelStr='time|psd';
end
callbackStr='moddemo(''modulate'');';
% Generic button information
btnPos=[left yPos-btnHt btnWid btnHt];
dispHndl=uicontrol( ...
'Style','popupmenu', ...
'Units','normalized', ...
'Position',btnPos, ...
'String',labelStr, ...
'Interruptible','on', ...
'Callback',callbackStr);
%====================================
% The WAVEFORM Menu
menuNumber=2;
yPos=menutop-(menuNumber-1)*(btnHt+spacing);
labelStr='speech|sine|square|triangle';
callbackStr='moddemo(''changewave'');';
% Generic button information
btnPos=[left yPos-btnHt btnWid btnHt];
waveHndl=uicontrol( ...
'Style','popupmenu', ...
'Units','normalized', ...
'Position',btnPos, ...
'String',labelStr, ...
'Interruptible','on', ...
'Callback',callbackStr);
%===================================
% Carrier frequency label and text field
top = yPos - btnHt - spacing;
labelWidth = frmWidth-textWidth-.01;
labelBottom = top-textHeight;
labelLeft = left;
labelPos = [labelLeft labelBottom labelWidth textHeight];
h = uicontrol( ...
'Style','text', ...
'Units','normalized', ...
'Position',labelPos, ...
'HorizontalAlignment','left', ...
'String','Fc', ...
'Interruptible','off', ...
'BackgroundColor',[0.5 0.5 0.5], ...
'ForegroundColor','white');
% Text field
textPos = [labelLeft+labelWidth labelBottom textWidth textHeight];
callbackStr = 'moddemo(''setFc'')';
FcHndl = uicontrol( ...
'Style','edit', ...
'Units','normalized', ...
'Position',textPos, ...
'HorizontalAlignment','center', ...
'Background','white', ...
'Foreground','black', ...
'String','400','Userdata',400, ...
'callback',callbackStr);
%===================================
% Sampling frequency label and text field
labelBottom=top-2*textHeight-spacing;
labelLeft = left;
labelPos = [labelLeft labelBottom labelWidth textHeight];
h = uicontrol( ...
'Style','text', ...
'Units','normalized', ...
'Position',labelPos, ...
'String','Fs', ...
'HorizontalAlignment','left', ...
'Interruptible','off', ...
'Background',[0.5 0.5 0.5], ...
'Foreground','white');
% Text field
textPos = [labelLeft+labelWidth labelBottom textWidth textHeight];
callbackStr = 'moddemo(''setFs'')';
FsHndl = uicontrol( ...
'Style','edit', ...
'Units','normalized', ...
'Position',textPos, ...
'HorizontalAlignment','center', ...
'Background','white', ...
'Foreground','black', ...
'String','2000','Userdata',2000, ...
'Callback',callbackStr);
%====================================
% AM radio button
btnTop = labelBottom-spacing;
btnNumber=1;
yPos=btnTop-(btnNumber-1)*(btnHt+spacing);
labelStr='AM';
callbackStr='moddemo(''radio'',1,''am'');';
% Generic button information
btnPos=[left yPos-btnHt btnWid btnHt];
btn1Hndl=uicontrol( ...
'Style','radiobutton', ...
'Units','normalized', ...
'Position',btnPos, ...
'String',labelStr, ...
'value',1,'Userdata','am', ...
'Callback',callbackStr);
%====================================
% AMSSB radio button
btnTop = labelBottom-spacing;
btnNumber=2;
yPos=btnTop-(btnNumber-1)*(btnHt+spacing);
labelStr='AMSSB';
callbackStr='moddemo(''radio'',2,''amssb'');';
% Generic button information
btnPos=[left yPos-btnHt btnWid btnHt];
btn2Hndl=uicontrol( ...
'Style','radiobutton', ...
'Units','normalized', ...
'Position',btnPos, ...
'String',labelStr, ...
'value',0, ...
'Callback',callbackStr);
%====================================
% FM radio button
btnNumber=3;
yPos=btnTop-(btnNumber-1)*(btnHt+spacing);
labelStr='FM';
callbackStr='moddemo(''radio'',3,''fm'');';
% Generic button information
btnPos=[left yPos-btnHt btnWid btnHt];
btn3Hndl=uicontrol( ...
'Style','radiobutton', ...
'Units','normalized', ...
'Position',btnPos, ...
'String',labelStr, ...
'Callback',callbackStr);
%====================================
% PM radio button
btnNumber=4;
yPos=btnTop-(btnNumber-1)*(btnHt+spacing);
labelStr='PM';
callbackStr='moddemo(''radio'',4,''pm'');';
% Generic button information
btnPos=[left yPos-btnHt btnWid btnHt];
btn4Hndl=uicontrol( ...
'Style','radiobutton', ...
'Units','normalized', ...
'Position',btnPos, ...
'String',labelStr, ...
'Callback',callbackStr);
%====================================
% "Play original" button
btnNumber=5;
yPos=btnTop-(btnNumber-1)*(btnHt+spacing);
labelStr='Play orig';
callbackStr='moddemo(''playsound'',1);';
% Generic button information
btnPos=[left yPos-btnHt btnWid btnHt];
playorigHandl=uicontrol( ...
'Style','pushbutton', ...
'Units','normalized', ...
'Position',btnPos, ...
'String',labelStr, ...
'Callback',callbackStr);
%====================================
% "Play mod" button
btnNumber=6;
yPos=btnTop-(btnNumber-1)*(btnHt+spacing);
labelStr='Play mod';
callbackStr='moddemo(''playsound'',2);';
% Generic button information
btnPos=[left yPos-btnHt btnWid btnHt];
playmodHndl=uicontrol( ...
'Style','pushbutton', ...
'Units','normalized', ...
'Position',btnPos, ...
'String',labelStr, ...
'Callback',callbackStr);
%====================================
% "Play demod" button
btnNumber=7;
yPos=btnTop-(btnNumber-1)*(btnHt+spacing);
labelStr='Play demod';
callbackStr='moddemo(''playsound'',3);';
% Generic button information
btnPos=[left yPos-btnHt btnWid btnHt];
playdemodHndl=uicontrol( ...
'Style','pushbutton', ...
'Units','normalized', ...
'Position',btnPos, ...
'String',labelStr, ...
'Callback',callbackStr);
%====================================
% Message box in center of figure - usually invisible
messageHndl = uicontrol('style','edit',...
'string','Resampling speech waveform ...',...
'units','normalized',...
'position',[.15 .45 .5 .15],...
'max',2,...
'visible','off');
%====================================
% The INFO button
labelStr='Info';
callbackStr='moddemo(''info'')';
helpHndl=uicontrol( ...
'Style','pushbutton', ...
'Units','normalized', ...
'Position',[left frmBottom+btnHt+spacing btnWid btnHt], ...
'String',labelStr, ...
'Callback',callbackStr);
%====================================
% The CLOSE button
labelStr='Close';
callbackStr='close(gcf)';
closeHndl=uicontrol( ...
'Style','pushbutton', ...
'Units','normalized', ...
'Position',[left frmBottom btnWid btnHt], ...
'String',labelStr, ...
'Callback',callbackStr);
hndlList=[origHndl modHndl demodHndl waveHndl ...
FcHndl FsHndl dispHndl btn1Hndl btn2Hndl btn3Hndl ...
btn4Hndl messageHndl helpHndl closeHndl];
set(figNumber, ...
'Visible','on', ...
'UserData',hndlList);
set(gcf,'Pointer','watch');
drawnow
moddemo('changewave')
set(gcf,'Pointer','arrow');
set(0,'ShowHiddenHandles',shh)
return
elseif strcmp(action,'setFc'),
hndlList=get(gcf,'Userdata');
filtHndl = hndlList(6);
v = get(gco,'Userdata');
s = get(gco,'String');
vv = eval(s,num2str(v));
Fs = get(filtHndl,'UserData');
if vv<0, vv = v; end
vv = round(vv);
if vv>Fs/2
waitfor(msgbox({'Sorry, the carrier frequency Fc must be at most'...
'half the sampling frequency Fs.'},...
'Moddemo Error','error','modal'))
vv = v;
end
set(gco,'Userdata',vv,'String',num2str(vv))
if vv == v
return
end
moddemo('modulate')
elseif strcmp(action,'setFs'),
fig = gcf;
set(fig,'Pointer','watch');
hndlList=get(fig,'Userdata');
waveHndl = hndlList(4);
FcHndl = hndlList(5);
FsHndl = hndlList(6);
messageHndl = hndlList(12);
v = get(gco,'Userdata');
s = get(gco,'String');
vv = eval(s,num2str(v));
if vv<=0, vv = v; end
Fc = get(FcHndl,'UserData'); % Carrier frequency
vv = round(vv*10)/10;
if Fc>vv/2
waitfor(msgbox({'Sorry, the sampling frequency Fs must be at least'...
'twice the carrier frequency Fc.'},...
'Moddemo Error','error','modal'))
vv = v;
end
if vv<30
waitfor(msgbox(['Sorry, the sampling frequency Fs' ...
' must be at least 30.'],...
'Moddemo Error','error','modal'))
vv = v;
end
set(gco,'Userdata',vv,'String',num2str(vv))
if vv == v
set(fig,'Pointer','arrow');
return
end
waveform = get(waveHndl,'value');
if waveform==1, % speech waveform - have to use resample
modHndl = hndlList(2);
w = get(waveHndl,'userdata');
[p,q] = rat(vv/7418,.0001);
makeinvislist = [modHndl get(modHndl,'children')' get(modHndl,'ylabel')];
set(messageHndl,'string',...
sprintf('Resampling waveform at %g/%g\ntimes original rate ...',p,q));
set(makeinvislist,'visible','off')
set(messageHndl,'visible','on')
drawnow
load mtlb
yy = resample(mtlb,p,q);
tt = (0:length(yy)-1)'/vv;
set(waveHndl,'userdata',[tt yy]);
set(messageHndl,'visible','off')
set(makeinvislist,'visible','on')
moddemo('modulate')
else
Fs = get(FsHndl,'UserData'); % Sampling frequency
Fc = get(FcHndl,'UserData'); % Carrier frequency
moddemo('changewave',Fc,Fs)
end
return
elseif strcmp(action,'changewave')
% create new waveform and stuff it into userdata of popup,
% then call moddemo('modulate')
set(gcf,'Pointer','watch');
axHndl=gca;
hndlList=get(gcf,'Userdata');
origHndl = hndlList(1);
modHndl = hndlList(2);
demodHndl = hndlList(3);
waveHndl = hndlList(4);
FcHndl = hndlList(5);
FsHndl = hndlList(6);
waveform = get(waveHndl,'value');
if waveform==2,
if nargin<2
Fc = 400;
Fs = 2000;
else
Fc = s;
Fs = ss;
end
t = (0:1/Fs:2)';
y = sin(2*pi*t);
elseif waveform==3,
if nargin<2
Fc = 400;
Fs = 2000;
else
Fc = s;
Fs = ss;
end
t = (0:1/Fs:2)';
y = square(2*pi*t);
elseif waveform==4,
if nargin<2
Fc = 400;
Fs = 2000;
else
Fc = s;
Fs = ss;
end
t = (0:1/Fs:2)';
y = sawtooth(2*pi*t,.5);
elseif waveform==1,
load mtlb
Fc = 2000;
Fs = 7418;
y = mtlb;
t = (0:length(y)-1)'/Fs;
end
set(FcHndl,'string',num2str(Fc),'userdata',Fc);
set(FsHndl,'string',num2str(Fs),'userdata',Fs);
set(waveHndl,'userdata',[t y])
moddemo('modulate')
return
elseif strcmp(action,'playsound'),
set(gcf,'Pointer','watch');
hndlList=get(gcf,'Userdata');
modHndl = hndlList(2);
waveHndl = hndlList(4);
FcHndl = hndlList(5);
FsHndl = hndlList(6);
btn1Hndl = hndlList(8);
messageHndl = hndlList(12);
Fc = get(FcHndl,'UserData'); % carrier frequency
Fs = get(FsHndl,'UserData'); % Sampling frequency
method = get(btn1Hndl,'Userdata');
y = get(waveHndl,'userdata');
y = y(:,2);
if s == 1, % original
sstr = 'original';
elseif s == 2, % modulated
sstr = 'modulated';
elseif s == 3, % demodulated
sstr = 'demodulated';
end
c = computer;
if (strcmp(c,'SUN4') | strcmp(c,'HP700') | strcmp(c,'SOL2'))
play_Fs = 8192;
else
play_Fs = Fs;
end
str = sprintf('Playing %s waveform \nat %g Hz ...',sstr,play_Fs);
set(messageHndl,'string',str)
makeinvislist = [modHndl get(modHndl,'children')' get(modHndl,'ylabel')];
set(makeinvislist,'visible','off')
set(messageHndl,'visible','on')
drawnow
if s >= 2 % need to compute modulated or demodulated wave
if strcmp(method,'fm')
kf = (Fc/Fs)*pi/2;
y1 = modulate(y,Fc,Fs,method,kf);
if s == 3
y2 = (1/kf)*demod(y1,Fc,Fs,method);
end
elseif strcmp(method,'pm')
kp = pi/2/max(max(abs(y)));
y1 = modulate(y,Fc,Fs,method,kp);
if s == 3
y2 = (1/kp)*demod(y1,Fc,Fs,method);
end
else
y1 = modulate(y,Fc,Fs,method);
if s == 3
y2 = demod(y1,Fc,Fs,method);
end
end
end
if s == 1
soundStr = 'soundsc(y,play_Fs)';
elseif s == 2
soundStr = 'soundsc(y1,play_Fs)';
elseif s == 3
soundStr = 'soundsc(y2,play_Fs)';
end
eval(soundStr,'') % catch errors in case no sound capabilities
set(messageHndl,'visible','off')
set(makeinvislist,'visible','on')
set(gcf,'Pointer','arrow');
return
elseif strcmp(action,'radio'),
axHndl=gca;
hndlList=get(gcf,'Userdata');
for i=8:11,
set(hndlList(i),'value',0) % Disable all the buttons
end
set(hndlList(s+7),'value',1) % Enable selected button
set(hndlList(8),'Userdata',ss) % Remember selected button
moddemo('modulate')
return
elseif strcmp(action,'modulate'), % modulate, demodulate, and update display
set(gcf,'Pointer','watch');
axHndl=gca;
hndlList=get(gcf,'Userdata');
origHndl = hndlList(1);
modHndl = hndlList(2);
demodHndl = hndlList(3);
waveHndl = hndlList(4);
FcHndl = hndlList(5);
FsHndl = hndlList(6);
dispHndl = hndlList(7);
btn1Hndl = hndlList(8);
btn2Hndl = hndlList(9);
btn3Hndl = hndlList(10);
btn4Hndl = hndlList(11);
set(gcf,'nextplot','add')
edgecolor = get(gca,'colororder'); edgecolor = edgecolor(1,:);
Fs = get(FsHndl,'UserData'); % Sampling frequency
Fc = get(FcHndl,'UserData'); % Carrier frequency
w = get(waveHndl,'userdata');
t = w(:,1); y = w(:,2);
method = get(btn1Hndl,'Userdata');
if strcmp(method,'fm')
% kf = (Fc/Fs)*2*pi/max(abs(y));
kf = (Fc/Fs)*pi/2;
y1 = modulate(y,Fc,Fs,method,kf);
y2 = (1/kf)*demod(y1,Fc,Fs,method);
elseif strcmp(method,'pm')
kp = pi/2/max(max(abs(y)));
y1 = modulate(y,Fc,Fs,method,kp);
y2 = (1/kp)*demod(y1,Fc,Fs,method);
else
y1 = modulate(y,Fc,Fs,method);
y2 = demod(y1,Fc,Fs,method);
end
if get(dispHndl,'value')==1, % time waveform
axes(origHndl), plot(t,y), grid on
ylabel('Original')
axes(modHndl), strips(y1,(length(y1)-1)/8/Fs,Fs), grid on
ylabel('Modulated')
axes(demodHndl), plot(t,y2), grid on
ylabel('Demodulated')
xlabel('Time (Seconds)')
elseif get(dispHndl,'value')==2, % psd
[Y,f] = psd(y,1024,Fs,500,0,'none');
[Y1,f] = psd(y1,1024,Fs,500,0,'none');
[Y2,f] = psd(y2,1024,Fs,500,0,'none');
Y = 10*log10(Y);
Y1 = 10*log10(Y1);
Y2 = 10*log10(Y2);
axes(origHndl), plot(f,Y), grid on, ylabel('Original')
axes(modHndl), plot(f,Y1), grid on, ylabel('Modulated')
axes(demodHndl), plot(f,Y2), grid on, ylabel('Demodulated')
xlabel('Frequency (Hz)')
set(hndlList(1:3),'ylim', ...
[max(max(min([Y Y1 Y2])),-120) max(max([Y Y1 Y2]))],'xlim',[0 Fs/2])
else % specgram
k = 150;
wind = kaiser(128,5);
nwind = length(wind);
noverlap = max(fix((length(y) - k*nwind) / (1-k)),0);
[b,f,t] = specgram(y,128,Fs,wind,noverlap);
[b1,f,t] = specgram(y1,256,Fs,wind,noverlap);
[b2,f,t] = specgram(y2,128,Fs,wind,noverlap);
Y1 = 10*log10(abs(b1+eps));
clims = [min(min(Y1)) max(max(Y1))];
axes(modHndl), imagesc(t,f,Y1), axis xy, colormap(jet)
ylabel('Modulated')
axes(origHndl), imagesc(t,f,10*log10(abs(b+eps)),clims)
axis xy, colormap(jet)
ylabel('Original')
axes(demodHndl), imagesc(t,f,10*log10(abs(b2+eps)),clims)
axis xy, colormap(jet)
ylabel('Demodulated')
xlabel('Time (Seconds)')
end
set(gcf,'Pointer', 'arrow')
return
elseif strcmp(action,'info'),
set(gcf,'pointer','arrow')
ttlStr = get(gcf,'Name');
hlpStr1= [...
' This demo lets you experiment with 4 different '
' modulation schemes. They are: '
' '
' AM - amplitude modulation '
' AMSSB - amplitude modulation, single side- '
' band '
' FM - frequency modulation '
' PM - phase modulation '
' '
' The demo uses MODULATE and DEMOD in the '
' Signal Processing Toolbox to implement '
' these schemes. '
' '
' The message signal is displayed in the top left '
' plot. Its modulated version is displayed in the '
' middle left plot. The demodulated version of '
' the modulated signal (the "reconstructed" '
' waveform) is displayed in the bottom left plot. ' ];
hlpStr2 = [...
' The popup menus on the upper right of the '
' figure control: '
' '
' - how to display the signals (upper popup) '
' CHOICES: '
' time - time domain waveform '
' psd - power spectral density (frequency '
' domain) '
' specgram - spectrogram (time AND '
' frequency domain) [NOT AVAILABLE '
' IN STUDENT EDITION] '
' - which message signal to use (lower popup) '
' CHOICES: '
' speech - digitized speech waveform, '
' originally sampled at 7418 Hz. '
' sine, square, triangle - 2 seconds worth '
' of 1 Hertz basic waveforms. '];
hlpStr3 = [...
' Fc and Fs are the carrier and sampling '
' frequencies, respectively, in Hertz. '
' '
' In each modulation scheme, a "carrier signal" '
' (cosine) of frequency Fc is altered in some '
' way by the message signal: '
' AM - amplitude of carrier is message signal '
' AMSSB - two carriers (one cosine, one sine) '
' are modulated by the message signal and '
' its Hilbert transform respectively, and '
' added together '
' FM - instantaneous frequency of carrier is '
' message signal '
' PM - instantaneous phase of carrier is '
' message signal '
' '
' The "Play ..." buttons let you listen to the '
' signals on most computers. '];
myFig = gcf;
helpfun(ttlStr,hlpStr1,hlpStr2,hlpStr3);
elseif strcmp(action,'closehelp'),
% Restore close button help behind helpfun's back
ch = get(gcf,'ch');
for i=1:length(ch),
if strcmp(get(ch(i),'type'),'uicontrol'),
if strcmp(lower(get(ch(i),'String')),'close'),
callbackStr = get(ch(i),'callback');
k = findstr('; moddemo(',callbackStr);
callbackStr = callbackStr(1:k-1);
set(ch(i),'callback',callbackStr)
break;
end
end
end
ch = get(0,'ch');
if ~isempty(find(ch==s)), figure(s), end % Make sure figure exists
end % if strcmp(action, ...lose all