hi neil, for a single frequency channel correlator (continuum correlator), an XF architecture (lag correlator) is the way to go, the number of antennas in your correlator will likely be limited by the number of signals you can get into the FPGA. (the correlator will be I/O bound, not compute bound, assuming you have a large FPGA).
i haven't looked at the number of LVDS inputs available on a large FPGA recently, but i think for a ~1800 pin package, there might be up to ~~512 LVDS pairs (1024 pins). if so, you can have 512 digitizers, which is 256 complex digitizers, which is 128 antennas dual pol, or 256 antenna single pol. as david hawkins suggested, could also use the high speed serdes on the FPGA. the new pricy FPGAs have serdes that can work at >100 Gbps. and the larger pricy FPGAs have 32 of these serdes, which means you can send 3.2 Tbits/sec into those FGPAs. that data rate is 3200 real 1Gsps bit streams, or 1600 complex streams at 1Gcomplexsamples/sec, or 800 antennas dual pol. but it would take a lot of electronics to convert 100 1Gbit/sec signals into a 100Gbit/sec signal - the easiest way to convert 100 signals into a single 100Gsps signal would be to use an FPGA, and that would defeat your goal of using a single FPGA for your correlator. best wishes, dan On Sat, Nov 11, 2023 at 12:43 PM salmon.na via casper@lists.berkeley.edu < casper@lists.berkeley.edu> wrote: > Thanks Dan, > > > > Yes, one antenna for one receiver, and there is only one frequency > channel, and a single polarisation, so quite a simple configuration. > > > > A good idea to use differential inputs as single bit ADCs. > > > > So the FX correlator looks the better architecture. > > > > So are you saying the FPGA FX correlator would manage making the > cross-correlations of 512 single bit channels at 1 GbpS, on say a single > FPGA, Xilinx or Altera ? > > > > Cheers, > > Neil > > > > *From:* casper@lists.berkeley.edu <casper@lists.berkeley.edu> *On Behalf > Of *Dan Werthimer > *Sent:* 11 November 2023 20:23 > *To:* casper@lists.berkeley.edu > *Subject:* Re: [casper] state of the art single bit correlators > > > > > > hi neil, > > > > by number of receiver channels, i presume you mean number of antennas? > > are these single or dual polarization? > > > > how many spectral channels do you need in your correlator ? > > > > for a large number of spectral channels, > > you'll likely want to use an FX architecture correlator (not XF). > > in an FX correlator the number of ADC bits doesn't change the FPGA > utilization for the DSP very much. > > > > one fun thing you can do with a 1 bit correlator, is use the LVDS > differential inputs on the FPGA as 1 Gsps digitizers. on a large FPGA > with a lot of pins you can get about 512 ADC's > > (256 antennas, dual pol) built into the FPGA, so the FPGA can be your > digitizer and your correlator... > > > > if you only need a small number of spectral channels, you could build an > XF correlator > > with ~512 inputs... (~256 antennas, dual pol, or ~512 antennas single > pol) in a large FPGA. > > > > with an XF architecture, the FPGA utilization is J x > number_of_spectral_channels. > > for FX, the utilization goes as K x log_base_2(spectral_channels). > > > > but constant K >> constant J, > > so sometimes (rarely) it is better to use XF, depending on the number of > spectral channels. > > > > > > best wishes, > > > > dan > > > > > > > > On Sat, Nov 11, 2023 at 11:47 AM salmon.na via casper@lists.berkeley.edu < > casper@lists.berkeley.edu> wrote: > > For a paper on non-radioastronomy aperture synthesis technology I need to > know how many receiver channels can run into an almost top of the range > FPGA optimally designed single-bit cross-correlator running a 2 Gbps. So > each receiver is digitised (sine and cosine) in single bits 1 Gbps. I’m > wondering if there are scaling laws for this and I only need to have a ball > park figure, ie a precision of say a factor of three or thereabouts. Any > associate papers related to that which might have clues to the capabilities > would be helpful. > > > > Many thanks, > > Neil Salmon > > -- > 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/005601da14d7%24ede171b0%24c9a45510%24%40tiscali.co.uk > <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/005601da14d7%24ede171b0%24c9a45510%24%40tiscali.co.uk?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_vEdvQAJ9Q5-JOAS1QfJ%3DW8AfQMU9D48cnt_gQ56GA%3DqiA%40mail.gmail.com > <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAGHS_vEdvQAJ9Q5-JOAS1QfJ%3DW8AfQMU9D48cnt_gQ56GA%3DqiA%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/007b01da14df%24a643ba90%24f2cb2fb0%24%40tiscali.co.uk > <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/007b01da14df%24a643ba90%24f2cb2fb0%24%40tiscali.co.uk?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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