Hi Dale, I’ll offer a few bullets on SWARM, the new SMA system.
1. SWARM is all open source and shared via CASPER and you are welcome to use it as is, or develop it further to adapt it to a new application, indeed it would be very pleasing to see the design used in some other instrument. 2. There is a paper which is worth reading to understand what SWARM is and what it does. Take a careful look if you are contemplating using the design. http://www.worldscientific.com/doi/pdf/10.1142/S2251171716410063 <http://www.worldscientific.com/doi/pdf/10.1142/S2251171716410063> You can get insight the paper without looking at the gory details of source codes, both bitcodes and associated software, but if you want to dig even deeper, sources are all shared here: http://www.github.com/sma-wideband. 3. You are correct SWARM processes 2 GHz blocks of *usable” bandwidth. The Nyquist band is somewhat wider, 2.288 GHz. That Nyquist band is divided into 16,384 channels (not 1024), so in fact it exceeds (rather than falls short of) your requirement for at least 4096 channels. 4. With all of the above the positive aspects, now comes the cautionary remark: it is by no means trivial to expand SWARM from 8 dual polarization antennas to 16 antennas. The X-engine would then have to process roughly 4x the number of baselines as for SWARM. This may well push the ROACH2 too far—we struggled to meet timing on the highly utilized ROACH2 for SWARM (286 MHz FPGA fabric clock). We are also looking at porting SWARM to newer platforms, primarily to expand bandwidth in the SMA’s case, rather than number of antennas. We have also studied application of CASPER-like methods to ALMA, which of course has far more than 8 antennas, but those studies were on paper, we have yet to reduce to real design. Taking SWARM as-is (8 antennas 2 GHz 16384 channels on ROACH2) is fairly simple. Expanding SWARM to 16 antennas and/or porting to a new FPGA platform will be a significant project—the SWARM design may be an excellent starting point, but even so. SKARAB is an interesting platform but doesn’t presently support the appropriate ADC. Not sure about SNAP2 I’ll leave that assessment to others. Best wishes. Jonathan > On Nov 7, 2017, at 12:29 PM, Gary, Dale E. <dale.e.g...@njit.edu> wrote: > > Dear Jonathan (and the rest of the CASPER list, in case anyone has additional > comments), > > I am looking into a new project that would require processing around 2 GHz of > bandwidth on of-order 10 (but more than 8) dual-polarization antennas. Our > science case calls for at least 4096 frequency channels. My understanding is > that the SMA correlator design is for a similar bandwidth, for 8 dual-pol > antennas, but 1024 channels or something similar. We do not want to spend a > lot of resources on correlator design, so my question is whether it is > possible and would it make sense to adapt the SMA design to a 16-antenna, > dual-pol, 4096-channel system, or whether it is better (or necessary) to > leave the ROACH-2 designs behind and move to one of the newer platforms? If > the latter, what digitizer bandwidths are available, and which board (SNAP2, > Scarab, others?) would be most appropriate to a new project of this scope? > > Thanks, > Dale -- 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 post to this group, send email to casper@lists.berkeley.edu.
