Sorry Jishnu, I didn't see the mixer question. If the mixer has a poorer dynamic range than the ADC, then the chain's DR is limited by that. So, as far as the mixer's DR is better than a 14 bit ADCs, it should be fine.
Mugundhan On Mon, Feb 10, 2020 at 1:38 PM Mugundhan vijayaraghavan < v.vaishnav151...@gmail.com> wrote: > 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> >> . >> > -- V. 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