Re: [Discuss-gnuradio] Can threading disturb sensing continuety

[kaleem ahmad]

Thanks Ed,

ADC sampling rate = 64MHz
it gives resulution time = 1/64MHz = 156 ns
if we choose N=512 for FFT then total observation time for one scan(one
complete FFT) is = 156ns x 512 = 8 micro sec
if the maximum possible (expected) cycle time is 200ms then:
it needs 200ms/8microsec = 2500 continues FFT scans to cover the range of
frequencies that correspond to 200ms cycle time.

Is above calculation correct?

The other possibility to increase the observation time is to increase the
FFT size, but to cover entire 200ms would need 200ms/1/64MHz = 12800000 =
FFT size (Which is not possible! Is it ???)

Now please comment if my above calculations are correct or not and secondaly
if my calculations are correct then how can I process (using GNURadio) 2500
cosective FFT's (with surety that no FFT in between these 2500 FFT's is
missing due to slow processing or thread switching) to find two peaks in a
single array (availability of two peaks will give me the oppertunity to
calculate the time distance between them).

Thanks and Best Regards

Ed Criscuolo-2 wrote:
> 
> 
> 
> kaleem ahmad wrote:
>> 
>> 3- Can you suggest some different way to solve this problem, The problem
>> is
>> simply to calculate the cycle time of some system which is already
>> working
>> in the environment 
>> 
> 
> 
> Since your unknown FSK signal has a regular cycle time, it should be
> relatively easy to detect.  For example, if your signal has a 1 ms
> cycle time, the low frequency spectrum should exhibit a large spike
> at 1 KHz.  It seems that all you would need is an fft that covers
> the range of frequencies that correspond to your possible cycle
> times.
> 
> @(^.^)@  Ed
> 
> 
> 
> 
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