Hi Ross, Just to add, we can also have the lo at 80mhz, and use the lower side band. 80 will be at 0, 20 will be at 60. But the band can be flipped offline. We can have a strong lpf at 60mhz, which can cut the lo off before downstream processing.
Mugundhan On Mon, 10 Feb 2020, 15:18 Mugundhan vijayaraghavan, < v.vaishnav151...@gmail.com> wrote: > Hi Ross, > > I'm not working with Colm on this. So I don't know about the resources > available to him. > > What you're saying is true. Doing it with a single stage may be > problematic as with 20 MHz LO, the there will be overlap of the side bands. > So, minimally, we need to have two stages. where the 20-80 MHz can be > up-converted to outside the band and then down-converted into the base band > of 0-60 MHz. > > Sorry for not being clear earlier. > > But anyway, for the RedPitaya, due to the sampling restrictions, 20-80 MHz > band has to be got into 0-60 MHz for getting the full band with the board. > > Thank you, > > Mugundhan > > On Mon, Feb 10, 2020 at 2:32 PM Ross Martin <ross.mar...@ieee.org> wrote: > >> Hi Mugundhan, >> >> Could you say a little more about how you're downconverting 20-80MHz to >> 0-60MHz? My understanding is that this is not easy to do while retaining >> signal quality. The band overlap of the input and output bands means >> simple conversion methods with normal mixers don't work. >> >> Ross >> >> >> On Mon, Feb 10, 2020, 1:09 AM 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> >>>> . >>>> >>> -- >>> 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/CAD560xm_P9M%3DaWWxuW47ZexoX4URR6as9egJaoL9%2BMK55_HJVA%40mail.gmail.com >>> <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAD560xm_P9M%3DaWWxuW47ZexoX4URR6as9egJaoL9%2BMK55_HJVA%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/CAG4nf71Ft-GeapgVxDLqhbkLC0cwkjy9KYna1zmbcDwSg_ZGRQ%40mail.gmail.com >> <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAG4nf71Ft-GeapgVxDLqhbkLC0cwkjy9KYna1zmbcDwSg_ZGRQ%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > > > -- > V. Mugundhan > > -- 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/CAD560xmKL6ca3v0mf_9hPjEHGZo6VRDt7PxY7C9WzqtsO0PS9Q%40mail.gmail.com.
