westocl wrote:
>> westocl wrote:
>>>> westocl wrote:
>>>>>> westocl wrote:
>>>>>>> Hello all.
>>>>>>>
>>>>>>> Is it feasable to do an fft in 'real time' on different 'blocks'
> of
>>>>> data?
>>>>>>> (i understand the nomenclature real time may be inappropriate).
>>>>>>>
>>>>>>>
>>>>>>> Im thinking, in general usage of an FFT, some x[n] comes in one
>>> sample
>>>>> at
>>>>>>> a time and fills up a buffer and when that buffer (lets call it
> 128
>>>>> time
>>>>>>> domain samples) is filled a FFT is taken and the 'output' is 128
>>> points
>>>>> of
>>>>>>> frequncy domain data.
>>>>>>>
>>>>>>> Now.. instad of somthing like a sliding DFT where a window
> evaluates
>>>>> the
>>>>>>> previous 127 samples along with one new one, i have a situation
>>> where
>>>>> i
>>>>>>> want to give the 'fft buffer' 128 NEW data points... so every
> single
>>>>> 'time
>>>>>>> instant'...128 new x[n] data are available.
>>>>>>>
>>>>>>> If this were done would I get a new FFT output at every time
>>> instant?
>>>>>> You confused me. 128 new instances of x[n] for every n? How?
>>>>>>
>>>>>> Jerry
>>>>>> --
>>>>>> Engineering is the art of making what you want from things you can
>>> get.
>>>>> You are right...My notation is somewhat confusing by using x[n].
> But
>>>>> imagine we had a switch that will switch to an already full buffer
> at
>>>>> every 'sample interval'. Then at the next instant we go to the next
>>> 128
>>>>> buffer and we call that x[n] and so on..
>>>> What fills these nearly full buffers? When? You seem to want 128 new
>>>> samples per sampling instant. That can't be sustained.
>>>>
>>>> Jerry
>>>> --
>>>> Engineering is the art of making what you want from things you can
> get.
>>>
>>> It seems thats exactly the case i will have... What i want to do is
>>> analagous to having 128 antennas and a situation where i have to take
> the
>>> FFT for each antenna. So some kind of rotary switch gives me the new
>>> antenna input data at every sample... and will keep spinning.
>> There's nothing unusual about simultaneously processing multiple
>> streams. But each stream would have it's own FT. There could be 128
>> samples collected at each sample interval, but probably not via a
>> multiplexer (rotary switch). One of us is still confused.
>>
>> Jerry
>> --
>> Engineering is the art of making what you want from things you can get.
>
>
> Ok, so are you saying i would need 128 different FFT blocks to do what i
> would like to do?

Of course. You can't smudge data from different sources into one grand
transform. (Caveat: you haven't yet explained what you want to accomplish.)

Jerry
--
Engineering is the art of making what you want from things you can get.