hi neil, regarding how big an FPGA you need:
let's assume 512 complex signals at 1 Gbit/sec real, 1 Gbit/sec imag: you'll need ~512^2 / 2 = 2^17 complex multipliers, which can be made from 2^18 four bit look up tables, assuming a 500 MHz FPGA clock. for the accumulators, you need 2^18 adders, 2^18 counters, and you'll also need 2^18 registers (for readout), assuming a 500 MHz clock. i think that will all fit into a giant FPGA, but it will be tight. i suggest you compile it and see. best wishes, dan Dan Werthimer Astronomy Dept and Space Sciences Lab University of California, Berkeley 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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