Hello Jason, This board sounds interesting although a full 1-GHz would be preferred. Is it the same board that Francois described or a different board? Thanks, -Bill.
________________________________ From: Jason Manley <jman...@ska.ac.za> To: Bill Petrachenko <wtpe...@yahoo.ca> Cc: Dan Werthimer <d...@ssl.berkeley.edu>; Casper <Casper@lists.berkeley.edu> Sent: Wednesday, May 30, 2012 9:19:48 AM Subject: Re: [casper] 1-2 GHz sampler MeerKAT's going to be using a 10-bit 1.8Gsps monolithic part. You won't quite get 1GHz bandwidth, but 900 is close. The ADC itself will do 2.2Gsps, but the external DMUX chip limits us to 1.8Gsps. There's another part with the DMUX integrated that will go faster, but then you'll have to layout your own ADC board. We're expecting the MeerKAT L-band ADC to be in production in a couple of months. This part gives some pretty impressive performance. Attached are some plots kindly provided by a non-CASPER collaborator who's played with it (Klasie Olivier from CSIR) for the integrated ADC/DMUX version. But as you've pointed out, this card won't run at full speed on ROACH-1 due to clocking limitations on the LVDS pins so we're using ROACH2s for full speed. Jason On 30 May 2012, at 14:57, Bill Petrachenko wrote: > OK, so it looks like I'll need to pay more attention to interleaving than I > had hoped. I assume there are no ROACH-compatible boards that use chips that > clock at 2048-MHz but without interleaving. > > Also, we're using a flexible down-converter to select 1-GHz bands anywhere in > the 2-14-GHz range. At many sites RFI at S-band will be a problem so dynamic > range is an issue. The chips on the ASIAA, ADC1x3000, and Kat-ADC all seem to > drop to about ENOB = 6-bits at 2-GHz which is less than ideal. Using a 10- or > 12-bit sampler would be preferred but it seems no ROACH-compatible sampler > boards have been designed with 10- or 12-bit capability and the interface > won't handle the extra bits anyway. Having said that though I seem to recall > that you implied in your initial email that the ASIAA card could be used in > the dual sampler mode (assuming a 1-GHz bandwidth) if interaced to the ROACH2 > and yet the ZDOK connection for both ROACH1 and ROACH2 both use a 40 > differential pair interface. How do you get the extra bandwith with the > ROACH2? > > Yes, I did pick up that we would need the higher bandwidth filter. However, I > also noticed that there were some plans to implement shields and heat sinks > for the Kat-ADC. Has this come to pass or has it become apparent that neither > are required? > > Many thanks, > -Bill. > > From: Dan Werthimer <d...@ssl.berkeley.edu> > To: Bill Petrachenko <wtpe...@yahoo.ca> > Sent: Monday, May 28, 2012 11:21:40 PM > Subject: Re: [casper] 1-2 GHz sampler > > the kat-adc has two different front end fiilter options. > make sure to order the filter option for high frequency. > > dan > > On Mon, May 28, 2012 at 7:19 PM, Bill Petrachenko <wtpe...@yahoo.ca> wrote: > > Thanks Dan. It sounds like the Kat-ADC is probably best for us. > > > > -Bill. > > > > ________________________________ > > From: Dan Werthimer <d...@ssl.berkeley.edu> > > To: Bill Petrachenko <wtpe...@yahoo.ca> > > Cc: Casper <Casper@lists.berkeley.edu> > > Sent: Monday, May 28, 2012 8:47:45 PM > > Subject: Re: [casper] 1-2 GHz sampler > > > > hi bill, > > > > i think all the boards you mention have analog bandwidth out to 2 GHz, > > so they should work well for your 1-2 GHz band. > > > > the asiaa board is the least expensive, but this board does not have > > programmable > > attenuators like the Kat-ADC. the asiaa board can be used as a single > > 5 Gsps ADC, or as a dual 2.5 GHz ADC. > > we have used the asiaa board as a single 5 gsps adc, and it works quite > > well. > > but we have never tested it as a dual adc - perhaps others reading > > this email can > > give you advice about using it in dual mode. if you are using roach > > I, you can't > > get the 8 bit version of the asiaa board working at the full 5 gsps. > > if you are using > > roach II, you can use it at 5 Gsps. > > > > best wishes, > > > > dan > > > > > > > > > > On Thu, May 24, 2012 at 11:30 AM, Bill Petrachenko <wtpe...@yahoo.ca> wrote: > >> I'm designing a digital data acquisition system using a ROACH1 board. I > >> need > >> to sample two Nyquist zones at 1024-2048 MHz. It appears that in the > >> Casper > >> group of products, a pair of ASIAA, ADC1x3000-8, or KatADC boards would > >> work > >> well and nicely interfaced to a single ROACH1 board (although the ASIAA > >> board is not mention explicitly on the web-site). Is there any reason to > >> choose one board over another? The gain adjustment stage is attractive on > >> the KatADC but the performance of the ADC1x3000-8 chip seems marginally > >> better at 2-GHz input frequency. The e2v chip seems less established than > >> the National chips. Is interleaving or calibration an issue for any of the > >> chips? > >> > >> I'd be grateful for any opinions on this. > >> Thanks, -Bill. > > > > > >
