Hi Cedric, Great, thanks for confirming that. One more question, if you don't mind?
If a narrow band signal is off-centre relative to one of my frequency bins, will the measured amplitude change each time I run the FFT? For example, if my FFT frequency bins are exactly 1 MHz wide (1024 pt FFT applied to 1 GSPS ADC data), and I am trying to measure a sinusoid with a frequency of 5.1 MHz, will the measured amplitude oscillate at a frequency of 0.1 MHz (5.1 MHz - 5 MHz)? Basically, my sampling (in terms of how often I sample the full time stream for the FFT) is out of phase with the signal to be measured? I probably didn't explain that very well, apologies. Best wishes, Colm On Fri, 28 Aug 2020 at 11:17, 'Cedric Viou' via [email protected] < [email protected]> wrote: > Hi Colm, > > You are right. > > PFB is a great way to reduce frequency smearing but the down-side is time > smearing. > > A brief event will be convolved with at least one of your PFB 8-tap > filters that end up feeding several FFT computations in a row. > So, you get time smearing for that short event... > > Regards, > > Cedric > > > Le 28/08/2020 à 11:56, Colm Bracken a écrit : > > Hi All, > > > > I have a question, which is probably DSP 101 basics, but I just wasn't > 100% sure. > > > > If I am applying a 1024 point FFT to a continuous time-stream from an > ADC with sampling ~ 1 GSPS, I will have a time resolution ~ 1 microsecond > (and frequency res. of ~ 1 MHz). > > > > But, if I instead apply an 8 tap PFB, am I essentially smearing out my > time resolution by a factor of 8, since I am now summing 8 rows of my 1024 > point time streams? > > I can't see how the number of PFB taps wouldn't affect my time > resolution. Or am I missing something? > > > > Thanks in advance, > > Colm > > > > -- > > > > *Dr Colm Bracken* > > Lecturer > > Maynooth University Experimental Physics > > > > > > Maynooth University, Maynooth, Co. Kildare, Ireland. > > > > T: +353 1 708 3641 > > E: [email protected] <mailto:[email protected]> W: > www.maynoothuniversity.ie <http://www.maynoothuniversity.ie> > > > > Follow my work on https://nuim.academia.edu/ColmBracken > > > > > > > > And > > > > > > Research Associate > > > > Astronomy & Astrophysics Section > > School of Cosmic Physics > > Dublin Institute for Advanced Studies > > 31 Fitzwilliam Place > > Dublin 2, D02 XF86 > > > > > > > > T: +353 1 440 6656 ext 352 > > E: [email protected] <mailto:[email protected]> W: > www.dias.ie/2017/06/22/dr-colm-bracken < > https://www.dias.ie/2017/06/22/dr-colm-bracken> > > > > Follow my work on https://nuim.academia.edu/ColmBracken > > > > -- > > You received this message because you are subscribed to the Google > Groups "[email protected]" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to [email protected] <mailto: > [email protected]>. > > To view this discussion on the web visit > https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAEx9wh9GmrYZ7_uLkXwSKqOp3GYm1Ei_0Bq-TPg9pt8LgQdprw%40mail.gmail.com > < > https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAEx9wh9GmrYZ7_uLkXwSKqOp3GYm1Ei_0Bq-TPg9pt8LgQdprw%40mail.gmail.com?utm_medium=email&utm_source=footer > >. > > -- > Cedric Viou <[email protected]> > > Ingénieur de recherche > > Station de Radioastronomie de Nançay, > Observatoire de Paris, PSL Research University, CNRS, Univ. Orléans, OSUC, > 18330 Nançay, France > http://www.obs-nancay.fr/ > > phone : +33 (0) 248 51 8609 > fax : +33 (0) 248 51 8318 > > www.openstreetmap.org/?mlat=47.381848&mlon=2.194415&zoom=18 > > -- > You received this message because you are subscribed to the Google Groups " > [email protected]" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/68a23cbf-5320-8b50-7a4f-52379c4a2ad7%40obs-nancay.fr > . > -- *Dr Colm Bracken* Lecturer Maynooth University Experimental Physics Maynooth University, Maynooth, Co. Kildare, Ireland. T: +353 1 708 3641 E: [email protected] W: www.maynoothuniversity.ie Follow my work on https://nuim.academia.edu/ColmBracken And Research Associate Astronomy & Astrophysics Section School of Cosmic Physics Dublin Institute for Advanced Studies 31 Fitzwilliam Place Dublin 2, D02 XF86 T: +353 1 440 6656 ext 352 E: [email protected] W: www.dias.ie/2017/06/22/dr-colm-bracken Follow my work on https://nuim.academia.edu/ColmBracken -- You received this message because you are subscribed to the Google Groups "[email protected]" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAEx9wh_2SWV5ahQ7x4bCegn9WkZ%3DPket18wO0QnLb%2BZx8JD7Lw%40mail.gmail.com.
