Sine signal with varied frequency in a matlab M-file

"Umutesi Faith" schrieb
> 
> The idea using the for loop was to get these
> frequencies at different time, i did not have any 
> other way on how to get these frequencies. 
>

Does the result of:

t1=(   0        : Ts :(N-200)*Ts );
t2=( (N-200)*Ts : Ts :(N-100)*Ts );
t3=( (N-100)*Ts : Ts :  (N-1)*Ts );
x1 = [sin(2*pi*f1*t1), 0.0*t2, 0.0*t3];
x2 = [0.0*t1, sin(2*pi*f2*t2), 0.0*t3];
x3 = [0.0*t1, 0.0*t2, sin(2*pi*f3*t3)];

look more like what you wanted?

HTH
Martin

PS: Please, don't top-post.

"Umutesi Faith" <ma_nz1@yahoo.com> wrote in message 
news:tu2dndyh14Z2vYHZnZ2dnUVZ_sadnZ2d@giganews.com...
> hi
>
> The idea using the for loop was to get these frequencies at different
> time, i did not have any other way on how to get these frequencies. Using
> the following code
> t=(0:Ts:(N-1)*Ts);
> x1 = sin(2*pi*f1*t);
> x2 = sin(2*pi*f2*t);
> x3 = sin(2*pi*f3*t);
> x = x1+x2+x3;
> figure, plot(x)
>
> i will just get these 3 frequencies but they exist at all time in the
> signal. This is the reason why i was trying to use t1, t2 and t3 and
> unfortunatly it seems no to do the work!
>
> Any suggestions
> thanks
>

% try this

Tone1_sampnum=112;

Tone2_sampnum=55;

nsample=256;

phi=zeros(nsample,1);

Tone3_sampnum=nsample-Tone2_sampnum-Tone1_sampnum; % should not be -ve so 
have a bit of sense eh?

Tone1_freq= 1188; % Hz

Tone2_freq=444; % Hz

Tone3_freq=777; % Hz

Fs=4000; % samples per second

start_time=0

end_time=(nsample-1)/Fs

deltaphaseT1=2*pi*Tone1_freq/Fs;

deltaphaseT2=2*pi*Tone2_freq/Fs;

deltaphaseT3=2*pi*Tone3_freq/Fs;

phi(1:Tone1_sampnum)=[0:Tone1_sampnum-1]*deltaphaseT1;

phi(Tone1_sampnum+(1:Tone2_sampnum))=phi(Tone1_sampnum)+[1:Tone2_sampnum]*deltaphaseT2;

phi(Tone2_sampnum+Tone1_sampnum+(1:Tone3_sampnum))=phi(Tone2_sampnum+Tone1_sampnum)+[1:Tone3_sampnum]*deltaphaseT3;

plot(sin(phi)),xlabel('sample number (starts at 1)')

figure

plot([0:nsample-1]/Fs,sin(phi)),xlabel('time axis (starts at 0)')

% your reader may reformat the lines by breaking long lines into shorter 
ones that matlab will not recognise unless you correct

Best of Luck - Mike

>Does the result of:---
>look more like what you wanted?

Yes, thanks a lot finally i could see the 3 frequencies at different time
along the signal which was exactly what i wanted. the idea here was that
when the first wave is generated so the other ones should be cancelled
(0.0*t2,0.0*t3)and so on. Did i understand this correctly? Anyway this
does the right thing!

x1 = [sin(2*pi*f1*t1), 0.0*t2, 0.0*t3];
>x2 = [0.0*t1, sin(2*pi*f2*t2), 0.0*t3];
>x3 = [0.0*t1, 0.0*t2, sin(2*pi*f3*t3)];

>
>HTH
>Martin
>
>PS: Please, don't top-post.
>
>
>
Thanks for the other suggestion, i could try it some other time.....

% your reader may reformat the lines by breaking long lines into shorter 
ones that matlab will not recognise unless you correct

Best of Luck - Mike


>

"Umutesi Faith" schrieb 
> 
> Yes, thanks a lot finally i could see the 3
> frequencies at different time along the signal which 
> was exactly what i wanted. 
Yes, I thought so from looking at the code.

> the idea here was that when the first wave is 
> generated so the other ones should be cancelled
> (0.0*t2,0.0*t3)and so on. 
> Did i understand this correctly? 
I don't quite understand the sentence, 
so I can't answer that one. 

The idea is that you generate a signal x composed
of three signals x1, x2, x3, each one only active during
a certain amount of time. 

The important thing to realize is (and this is were 
you probably went wrong) that the arrays x1,x2,x3 are
not indexed by ***time***, but are sequentially numbered
starting from 0 (just as plain C arrays are).

HTH
Martin

Ok thanks it helps it understand it this way!

>The idea is that you generate a signal x composed
>of three signals x1, x2, x3, each one only active during
>a certain amount of time. 
>
>>HTH
>Martin
>
>
>
>
>