hi friends
i have a basic doubt in plotting freq response.
i have written a fft computation program (64 point)on BF533 using
Visual DSP++ 5 software. am not able to plot this freq response.
In the sense if my input data is a 1K sine wave which is sampled
at 100K my freq response should give me a spike like at frequencies 1K,101K
etc.The same can be seen using MATLAB software
But in visualDSP++ 5 eventhough there is a plot option (view) i'm unable to
get the exact response. please do let me know.
FFT frequency response
Started by ●February 8, 2009
Reply by ●February 8, 20092009-02-08
On Sun, 8 Feb 2009, a...@rediffmail.com wrote:
> hi friends
> i have a basic doubt in plotting freq response.
> i have written a fft computation program (64 point)on BF533 using
> Visual DSP++ 5 software. am not able to plot this freq response.
> In the sense if my input data is a 1K sine wave which is sampled
> at 100K my freq response should give me a spike like at frequencies
>1K,101K etc.The same can be seen using MATLAB software
> But in visualDSP++ 5 eventhough there is a plot option (view) i'm
>unable to get the exact response. please do let me know.
You can't get a response at 101k if your sampling rate is 100k.
The highest frequency you can see is 50k. You should see 1k, 2k, 3k, 4k,
...depending on how good your sine wave generator is.
Look up Shannon and Nyquist theorems.
Patience, persistence, truth,
Dr. mike
> hi friends
> i have a basic doubt in plotting freq response.
> i have written a fft computation program (64 point)on BF533 using
> Visual DSP++ 5 software. am not able to plot this freq response.
> In the sense if my input data is a 1K sine wave which is sampled
> at 100K my freq response should give me a spike like at frequencies
>1K,101K etc.The same can be seen using MATLAB software
> But in visualDSP++ 5 eventhough there is a plot option (view) i'm
>unable to get the exact response. please do let me know.
You can't get a response at 101k if your sampling rate is 100k.
The highest frequency you can see is 50k. You should see 1k, 2k, 3k, 4k,
...depending on how good your sine wave generator is.
Look up Shannon and Nyquist theorems.
Patience, persistence, truth,
Dr. mike
Reply by ●February 10, 20092009-02-10
I remember that if a signal is sampled at fs, then its freq response
is given by
X(f-nfs)=X(f) where n=0,+/-1,+/-2.....
so if my signal is a 1k sine and i digitize it by sampling it
at 100k then according to the equation i'll get responses at
1k(fundamental), 101k (for n=-1) etc.
hi friends
>i have a basic doubt in plotting freq response.
>i have written a fft computation program (64 point)on BF533 using
>Visual DSP++ 5 software. am not able to plot this freq response.
>In the sense if my input data is a 1K sine wave which is sampled
>at 100K my freq response should give me a spike like at frequencies 1K,101K etc.The same can be seen using MATLAB software
>But in visualDSP++ 5 eventhough there is a plot option (view) i'm unable to get the exact response. please do let me know.
is given by
X(f-nfs)=X(f) where n=0,+/-1,+/-2.....
so if my signal is a 1k sine and i digitize it by sampling it
at 100k then according to the equation i'll get responses at
1k(fundamental), 101k (for n=-1) etc.
hi friends
>i have a basic doubt in plotting freq response.
>i have written a fft computation program (64 point)on BF533 using
>Visual DSP++ 5 software. am not able to plot this freq response.
>In the sense if my input data is a 1K sine wave which is sampled
>at 100K my freq response should give me a spike like at frequencies 1K,101K etc.The same can be seen using MATLAB software
>But in visualDSP++ 5 eventhough there is a plot option (view) i'm unable to get the exact response. please do let me know.
