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. 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