Hi Bill, Can you clarify: when you say you need an ADC "clocked at 2048 MHz" do you mean a sampling rate of 4096 MS/s or 2048 MS/s? (The ADC sample rate for some parts is twice the clock rate.) I'm a bit confused as to what you are after, looking back at your original framing of your problem, and some of the responses to it.
You said: > I need to sample two Nyquist zones at 1024-2048 MHz. Can you clarify which two Nyquist zones you mean? May have some more to say depending on your clarification. This application has a VLBI-recorder-like look . . . (apologies to all for spamming multiple copies on my last response will try not to do it again). Jonathan On May 30, 2012, at 9:18 AM, Francois Kapp wrote: > Hi Bill, > > Not quite yet, but we are working on a board that could do 2.2 GSPS > non-interleaved. It is called the adc1x2200-10 which indicates 1 channel, 10 > bits, 2200 MSPS. It is based on the e2v AT84AS008 part with associated DMUX > and the status is that we have a PCB design, PCB's and components ordered and > assembly booked. If all goes well we should be able to get some measurement > results out within the next two months. > > This may be an option depending on your schedule? > > Regards, > Francois > > On Wed, May 30, 2012 at 2:57 PM, Bill Petrachenko <[email protected]> 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 <[email protected]> > To: Bill Petrachenko <[email protected]> > 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 <[email protected]> wrote: > > Thanks Dan. It sounds like the Kat-ADC is probably best for us. > > > > -Bill. > > > > ________________________________ > > From: Dan Werthimer <[email protected]> > > To: Bill Petrachenko <[email protected]> > > Cc: Casper <[email protected]> > > 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 <[email protected]> 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. > > > > > > > > > > -- > Francois Kapp > > Sub-system Manager > Digital Back End > meerKAT > > SKA South Africa > Third Floor > The Park > Park Road (off Alexandra Road) > Pinelands > 7405 > Western Cape > South Africa > > Latitude: -33.94329 (South); Longitude: 18.48945 (East). > > (p) +27 (0)21 506 7300 > (p) +27 (0)21 506 7360 (direct) > (f) +27 (0)21 506 7375 > (m) +27 (0)82 787 8407
