I wouldn't be surprised if Ryan has a more clever way to do it, but one option is to use an extension of the method that Matt Morgan and Rick Fisher (i.e. http://www.gb.nrao.edu/electronics/edir/edir320.pdf) developed for I/Q imbalance compensation. Basically you make a filterbank with each of the cores separately, then multiply by a complex correction coefficient for each frequency channel of the filterbank and form the sum and difference to recover the whole corrected spectrum. This works for filterbank (including, I think, coherent filterbank) applications. In the IQ case this is analogous to Gram-Schmidt orthoginalization. I made a CASPER implementation of the IQ version a few years ago, but never developed it further than a demonstration. I think this idea should naturally extend to more than two ADC cores, but I haven't tried.
Glenn On Tue, May 29, 2012 at 6:44 AM, Paul Demorest <[email protected]> wrote: > Hi Ryan, > > We'd be interested in learning more about your interleave-fixing technique > as well. If JPL will let you tell us about it that would be great. If you > can't release detailed code/etc, even a high-level description of the > approach would be nice. > > Cheers, > Paul > > > On Mon, 28 May 2012, Ryan Monroe wrote: > >> I've used the ADC083000s before and the interleave can be pretty bad-- as >> much as 15% difference across their 3GHz spectrum! You should expect better >> performance because you only need to tune for 1GHz of bandwidth however. I >> can't speak for the other parts. >> >> I have a technique I've developed which cancels out all cross-board ADC >> interleaving issues. I've been trying to get JPL to let me release it to >> the public domain: I'll see what I can do, and please tell me if you have >> issues. >> >> --Ryan Monroe >> >> >> >> >> On 5/28/2012 5:47 PM, Dan Werthimer wrote: >>> >>> 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. >> >> >> >
