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FSK modulation

Started by John ●November 15, 2002
I'tyring to generate a bit stream that will be modulated using an FSK
signal. So far what I have is when I plotted the graph what I have
is not an FSK signal but a bit stream....

bit = round(rand(1,10)); % bit stream of random 1's and 0's
bitperiod = 0.1; %bit period
fs = 11025; %sampling frequency
fc = [1000 5000]; % carrier frequency
% create the FSK signal
transmitted = zeros(1,bit);
for k = 1:length(bit)
f = fc(bit(k) + 1);
transmitted(floor((k-1)*bitperiod*fs)+1: floor(k*bitperiod*fs)) =
cos(2*pi*f*(0:(bitperiod/fs):bitperiod)); % here's the trouble
% I'm having.
plot(transmitted)
end

Thanks guys for your help



Reply by navaneetha krishnan ●November 18, 20022002-11-18
The code you gave gives an assignment error. Is that
your problem. You have to rework the indices for
transmitted and time values for cos(x). They both
should be of same size which in your case is 1102.
After that I got something which looks like a cosine
wave.

Navan

--- John <> wrote:
> I'tyring to generate a bit stream that will be
> modulated using an FSK
> signal. So far what I have is when I plotted the
> graph what I have
> is not an FSK signal but a bit stream....
>
> bit = round(rand(1,10)); % bit stream of random 1's
> and 0's
> bitperiod = 0.1; %bit period
> fs = 11025; %sampling frequency
> fc = [1000 5000]; % carrier frequency
> % create the FSK signal
> transmitted = zeros(1,bit);
> for k = 1:length(bit)
> f = fc(bit(k) + 1);
> transmitted(floor((k-1)*bitperiod*fs)+1:
> floor(k*bitperiod*fs)) =
> cos(2*pi*f*(0:(bitperiod/fs):bitperiod)); % here's
> the trouble
> % I'm
> having.
> plot(transmitted)
> end
>
> Thanks guys for your help


__________________________________________________

Reply by ●November 18, 20022002-11-18
Hi John, in your code, you change the frequency f once a period.

This is much too often.

You better increase the sampling rate by x20 or so
and create more samples, or in other words, vary the
carrier frequency f much slower (linear interpolation or so)

Servus

Martin ----- Original Message -----
From: "John" <>
To: <>
Sent: Friday, November 15, 2002 1:58 PM
Subject: [matlab] FSK modulation > I'tyring to generate a bit stream that will be modulated using an FSK
> signal. So far what I have is when I plotted the graph what I have
> is not an FSK signal but a bit stream....
>
> bit = round(rand(1,10)); % bit stream of random 1's and 0's
> bitperiod = 0.1; %bit period
> fs = 11025; %sampling frequency
> fc = [1000 5000]; % carrier frequency
> % create the FSK signal
> transmitted = zeros(1,bit);
> for k = 1:length(bit)
> f = fc(bit(k) + 1);
> transmitted(floor((k-1)*bitperiod*fs)+1: floor(k*bitperiod*fs)) =
> cos(2*pi*f*(0:(bitperiod/fs):bitperiod)); % here's the trouble
> % I'm having.
> plot(transmitted)
> end
>
> Thanks guys for your help >
>
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Reply by digicomm ●November 18, 20022002-11-18
Hi John,

Enjoy it!

bit = round(rand(1,10)); % bit stream of random 1's and 0's
bitperiod = 1; %bit period
fs = 20; %sampling frequency
fc = [1 5]; % carrier frequency
% create the FSK signal
L=length(0:(bitperiod/fs):bitperiod);
transmitted = zeros(1,L);
for k = 1:length(bit)
f = fc(bit(k) + 1);
transmitted((k-1)*L+1: k*L) = cos(2*pi*f*(0:(bitperiod/fs):bitperiod));
stem(transmitted);
end

Best regards.

digicomm

----- 2002-11-15 21:58:00 "John"<> wrote: -----

>I'tyring to generate a bit stream that will be modulated using an FSK
>signal. So far what I have is when I plotted the graph what I have
>is not an FSK signal but a bit stream....
>
>bit = round(rand(1,10)); bit stream of random 1's and 0's
>bitperiod = 0.1; bit period
>fs = 11025; sampling frequency
>fc = [1000 5000]; carrier frequency
> create the FSK signal
>transmitted = zeros(1,bit);
>for k = 1:length(bit)
> f = fc(bit(k) + 1);
> transmitted(floor((k-1)*bitperiod*fs)+1: floor(k*bitperiod*fs)) =
>cos(2*pi*f*(0:(bitperiod/fs):bitperiod)); here's the trouble
> I'm having.
>plot(transmitted)
>end
>
>Thanks guys for your help >
>
>_____________________________________
>Note: If you do a simple "reply" with your email client, only the author of
this message will receive your answer. You need to do a "reply all" if you want
your answer to be distributed to the entire group.
>
>_____________________________________
>About this discussion group:
>
>To Join:
>
>To Post:
>
>To Leave:
>
>Archives: http://www.yahoogroups.com/group/matlab
>
>More DSP-Related Groups: http://www.dsprelated.com/groups.php3
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>">http://docs.yahoo.com/info/terms/
Reply by peter yip ●December 12, 20022002-12-12
Hi digicomm

I need help with my QPSK with a set of data bit to
extract. I am having great difficulties in modulating
and demodulating it. Would highly appreciate it if you
have a sample program for me to learn how to do it.

Your kind help is greatly appreciated.

regards
peter

--- digicomm <> wrote:
> Hi John,
>
> Enjoy it!
>
> bit = round(rand(1,10)); % bit stream of random 1's
> and 0's
> bitperiod = 1; %bit period
> fs = 20; %sampling frequency
> fc = [1 5]; % carrier frequency
> % create the FSK signal
> L=length(0:(bitperiod/fs):bitperiod);
> transmitted = zeros(1,L);
> for k = 1:length(bit)
> f = fc(bit(k) + 1);
> transmitted((k-1)*L+1: k*L) =
> cos(2*pi*f*(0:(bitperiod/fs):bitperiod));
> stem(transmitted);
> end
>
> Best regards.
>
> digicomm
>
> ----- 2002-11-15 21:58:00 "John"<>
> wrote: -----
>
> >I'tyring to generate a bit stream that will be
> modulated using an FSK
> >signal. So far what I have is when I plotted the
> graph what I have
> >is not an FSK signal but a bit stream....
> >
> >bit = round(rand(1,10)); bit stream of random 1's
> and 0's
> >bitperiod = 0.1; bit period
> >fs = 11025; sampling frequency
> >fc = [1000 5000]; carrier frequency
> > create the FSK signal
> >transmitted = zeros(1,bit);
> >for k = 1:length(bit)
> > f = fc(bit(k) + 1);
> > transmitted(floor((k-1)*bitperiod*fs)+1:
> floor(k*bitperiod*fs)) =
> >cos(2*pi*f*(0:(bitperiod/fs):bitperiod)); here's
> the trouble
> > I'm
> having.
> >plot(transmitted)
> >end
> >
> >Thanks guys for your help
> >
> >
> >
> >
> >_____________________________________
> >Note: If you do a simple "reply" with your email
> client, only the author of this message will receive
> your answer. You need to do a "reply all" if you
> want your answer to be distributed to the entire
> group.
> >
> >_____________________________________
> >About this discussion group:
> >
> >To Join:
> >
> >To Post:
> >
> >To Leave:
> >
> >Archives: http://www.yahoogroups.com/group/matlab
> >
> >More DSP-Related Groups:
> http://www.dsprelated.com/groups.php3
> >
> >">http://docs.yahoo.com/info/terms/
>
> >
>


__________________________________________________