Hi jishnu, With red pitaya, you have to down convert 20-80 to 0-60 baseband to use the band fully. As such, it has a cutoff at 65MHz.
Thanks, Mugundhan On Mon, 10 Feb 2020, 13:30 Jishnu Nambissan T, <jis...@rri.res.in> wrote: > Hi Mugundhan, > > With red pitaya, can you sample 20-80 MHz without downconversion ? And if > analog down conversion is required, wouldn't that restrict the usable > dynamic range (unless a high level mixer is used) ? > > Jishnu > > ------------------------------ > *From: *"Mugundhan vijayaraghavan" <v.vaishnav151...@gmail.com> > *To: *"casper" <casper@lists.berkeley.edu> > *Sent: *Thursday, February 6, 2020 1:06:09 AM > *Subject: *Re: [casper] Solar Spectrometer Channeliser > > Hi Dan, > > We have done integration times from 20ms upto a second. There are bursts > that last for hours, minutes and a few ms to seconds as well. > > We have not tried AGC on these bursts since we were aiming to study them > only. In the 8 bit design, we had 3 bits for background and remaining 5 to > accommodate bursts. > > The red pitaya can still be used if Colm can restrict the band to 20-80 > mhz, because the ionosphere starts cutting of anything below 20mhz > mostly(depending on the location of course). Then this can be down > converted to fit into 0-62.5 mhz base band of the red pitaya. > > Thanks, > > Mugundhan > > > > > On Wed, 5 Feb 2020, 22:23 Dan Werthimer, <d...@ssl.berkeley.edu> wrote: > >> >> hi mugundhan, >> >> what's the time scale for these bursts? >> rise and fall times? >> can you use a AGC circuit (automatic gain control), >> eg: computer controlled attenuator >> to turn down the power going into the ADC during the bursts, >> so you could keep the levels going into the ADC relatively constant? >> if the rise and fall times are longer than 1ms (the integration time of >> the spectrometer), >> then you could adjust the power level for each spectrum, and write down >> where >> you set the attenuator for that spectrum, so you could still know the >> absolute power. >> >> if not, there are some 14 bit 200 Msps ADC boards, and i think the new >> RFSOC boards/chips have 14 bit ADC's, >> but you'll have to write a casper yellow interface block for this ADC, >> as we don't have a 14 bit 200 Msps ADC in the casper library. >> >> another possiblity is to multiplex your 80 MHz band, 40 MHz at a time >> into a red pitaya board, >> ping ponging back and forth between bands: 0 to 40 MHz for 1 ms, then 40 >> to 80 MHz for the next ms. >> >> >> best wishes, >> >> dan >> >> >> >> >> On Wed, Feb 5, 2020 at 8:33 AM Mugundhan vijayaraghavan < >> v.vaishnav151...@gmail.com> wrote: >> >>> Hi Dan, >>> >>> Usually quiet sun doesn't show such abrupt changes, but bursts do >>> (easily 40-50dB or more) for bright bursts. We have built 8 bit >>> spectrometers in 40-80Mhz, but have found then when the burst is pretty >>> strong, saturation effects starts kicking in. >>> >>> >>> Thanks, >>> Mugundhan >>> >>> >>> On Wed, 5 Feb 2020, 21:52 Dan Werthimer, <d...@ssl.berkeley.edu> wrote: >>> >>>> >>>> hi colm, >>>> regarding dynamic range >>>> --------------------------------- >>>> for your solar spectrometer, do you need 14 bits of ADC dynamic range? >>>> it's very unusual in radio astronomy to need that much instantaneous >>>> dynamic range on the input. >>>> does the sun vary on short time scales in the radio band by factor of >>>> 1000 in voltage (1,000,000 in power) ? >>>> or do you have very strong bursting RFI that is 1000 times the average >>>> noise voltage (1M in power) in the whole band? >>>> >>>> as you probably know, you'll have lots more dynamic range in the output >>>> power spectrum than the dynamic range of the ADC: >>>> if you are building a 1024 channel spectrometer with 1 ms integration, >>>> you'll get about 8 bits more bits of dynamic range above your ADC >>>> dynamic range in frequency domain voltage, >>>> which is 16 bits more of dynamic range above your ADC dynamic range in >>>> power spectra. >>>> so you'll have about 20 bits of spectral dynamic range if you use an 8 >>>> bit ADC, >>>> (power spectrum dynamic range of about 1 million in 1 ms with an 8 bit >>>> ADC, setting noise at 3 bit RMS). >>>> and 24 bits of spectrral dynamic range for a 10 bit ADC, 28 bits for 12 >>>> bit ADC, and 32 bits for for 14 bit ADC). >>>> >>>> regarding boards for your spectrometer >>>> --------------------------------------------------- >>>> >>>> 1) as adam pointed out, the red pitaya is cheap, but sample rate and >>>> bandwidth don't quite get the specs you need. >>>> >>>> 2) another possibility is to use a snap board, which costs more, but >>>> can sample 3 inputs at 950 Msps, >>>> or 6 inputs at 500 Msps, or 12 inputs at 250 Msps with 8 bit ADC's. >>>> most people populate the snap board with 8 bit ADCs, >>>> but a few people have populated it with 12 bit ADC's, although the >>>> sample rate goes down by 8/12. >>>> >>>> 3) another possibility is to use a xilinx RFSOC board. the first gen >>>> has a bank of 12 bit ADC's (8 inputs at 4 Gsps, or 16 inputs at 2 Gsps), >>>> but i think the new generation has 14 bit ADC's ? the RFSOC boards >>>> cost more than snaps, but RFSOC was designed >>>> in dublin, so you can probably get one from xilinx dublin.... the >>>> ZCU111 board has not been fully casperized yet though. >>>> >>>> best wishes, >>>> >>>> dan >>>> >>>> >>>> >>>> >>>> >>>> Dan Werthimer >>>> Marilyn and Watson Alberts Chair >>>> Astronomy Dept and Space Sciences Lab >>>> University of California, Berkeley >>>> >>>> >>>> On Wed, Feb 5, 2020 at 5:06 AM Colm Bracken <colmbrac...@gmail.com> >>>> wrote: >>>> >>>>> Hello CASPER people, >>>>> >>>>> We are looking to build a spectrometer with not too demanding >>>>> requirements. >>>>> Based on the specs below, would the Red Pitaya be up to the job do you >>>>> think? >>>>> Or, is there another, better suited (but similarly affordable) >>>>> solution? >>>>> >>>>> Chanel widths: ~< 100 kHz >>>>> Time sampling: ~< millisecond >>>>> Polarisation: 2 channels >>>>> Antenna freq range: 10-85 MHz (total bandwidth of 75 MHz) >>>>> Digitisation: 14 bit >>>>> >>>>> Any advice on this would be great! >>>>> >>>>> Thanks in advance, >>>>> Colm >>>>> -- >>>>> >>>>> *Dr Colm Bracken* >>>>> Lecturer >>>>> Maynooth University Experimental Physics >>>>> >>>>> >>>>> Maynooth University, Maynooth, Co. Kildare, Ireland. >>>>> >>>>> T: +353 1 708 3641 >>>>> E: colm.brac...@mu.ie 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: cbrac...@cp.dias.ie 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 "casper@lists.berkeley.edu" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>> an email to casper+unsubscr...@lists.berkeley.edu. >>>>> To view this discussion on the web visit >>>>> https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAEx9wh8jNxeUnPGaSvwwuAtPCRsnNoCbOFnhbpU9EDb%2BPKh-Bg%40mail.gmail.com >>>>> <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAEx9wh8jNxeUnPGaSvwwuAtPCRsnNoCbOFnhbpU9EDb%2BPKh-Bg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>>> . >>>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "casper@lists.berkeley.edu" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to casper+unsubscr...@lists.berkeley.edu. >>>> To view this discussion on the web visit >>>> https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAGHS_vH-6MvNUAxsZVs8KOW%2BUhOB5tUAZQdmu3_%3D9A24RL1Fqw%40mail.gmail.com >>>> <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAGHS_vH-6MvNUAxsZVs8KOW%2BUhOB5tUAZQdmu3_%3D9A24RL1Fqw%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "casper@lists.berkeley.edu" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to casper+unsubscr...@lists.berkeley.edu. >>> To view this discussion on the web visit >>> https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAD560xkZtMmYT0huZPM-mR6z22Je00DVd7sSsEsDGwHP42KHGg%40mail.gmail.com >>> <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAD560xkZtMmYT0huZPM-mR6z22Je00DVd7sSsEsDGwHP42KHGg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "casper@lists.berkeley.edu" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to casper+unsubscr...@lists.berkeley.edu. >> To view this discussion on the web visit >> https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAGHS_vHPmfPup6dY-CwvwdOnk62W0DobD62V5StCaOJyv3fJ0g%40mail.gmail.com >> <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAGHS_vHPmfPup6dY-CwvwdOnk62W0DobD62V5StCaOJyv3fJ0g%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups " > casper@lists.berkeley.edu" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to casper+unsubscr...@lists.berkeley.edu. > To view this discussion on the web visit > https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAD560xkvm2SxZtiDu2OLUy3JW%2BUnj-wdEV5rG2G1m-Sp3cLmyQ%40mail.gmail.com > <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAD560xkvm2SxZtiDu2OLUy3JW%2BUnj-wdEV5rG2G1m-Sp3cLmyQ%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > > -- > You received this message because you are subscribed to the Google Groups " > casper@lists.berkeley.edu" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to casper+unsubscr...@lists.berkeley.edu. > To view this discussion on the web visit > https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/1753239181.40603.1581321602856.JavaMail.zimbra%40rri.res.in > <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/1753239181.40603.1581321602856.JavaMail.zimbra%40rri.res.in?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "casper@lists.berkeley.edu" group. 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