Super Fast ADC For Computer DSP Work - Page 1
Forum section: electronics / beginners

author: gamozo
author_rank: Regular Contributor
timestamp: August 15, 2013, 08:57:11 pm
content: Heya everyone.I'm interested in a really fast ADC (1Gsps-5Gsps, 8bits+) for doing DSP on my desktop. I don't need an FPGA unit, I just want a way to sample the data and get it on my computer. Ideally it'd be some sort of a PCIE card, but I wouldn't mind if it just gathered a few seconds of data on the card and then offloaded it via USB or something.I've been looking into Casper stuffhttps://casper.berkeley.edu/wiki/Hardware. This looks pretty cheap and in my range of requirements. I've also looked at individual ADCs. TI's ADC08B3000 is 3Gsps at 8 bits and costs $500 per ku. When I see Agilent and other big name brand acquisition stuff of the same speed, it's way beyond $500. I'm curious if anyone knows of open hardware projects similar to what I'm interested in that could help decrease the costs so I get extra bang for my buck.My budget is 1-5k USD.Use case? I just want it around to use for DSP and as an oscilloscope.TL;DR: I want to get a 1Gsps-5Gsps ADC with an ability to offload all the raw data to my computer (not necessarily in real-time). I'm not looking for a board that does DSP on it, I just want it to store the data to be pulled to my computer later.-Brandon

author: marshallh
author_rank: Unknown
timestamp: August 15, 2013, 09:17:10 pm
content: http://www.acquitek.com/news/data-acquisition-systems.html?art=1701http://www.adlinktech.com/Digitizer/index.phphttp://www.signatec.com/products/daq/high-speed-digitizer-board-px1500-2.html

author: fcb
author_rank: Super Contributor
timestamp: August 15, 2013, 09:19:16 pm
content: You could consider using interleaved ADC's to achieve the sample rate (such as the 500M/S AD9286) - this method also lowers the speed of your buffering solution (at the expense of width).

author: branadic
author_rank: Super Contributor
timestamp: August 15, 2013, 09:31:40 pm
content: For the budget you have you can buy more than one Rigol DS2202, so you have your scope with big memory (up to 140Mpt.) and can transfer and save data to your computer.You can also buy one of those USB scope front-ends within your budget (see Picoscope).

author: Christe4nM
author_rank: Unknown
timestamp: August 16, 2013, 12:23:28 pm
content: For that kind of speeds you are automatically limited to a flash ADC architecture. Those can be really fast, but are typically limited to 8-bits due to the amount of precision comparators needed. (Ever wondered why most oscilloscope are limited to 8-bits vertical resolution?) It might be possible to get a 10-bit flash ADC, but prepare to pay premium prices. The difference between commercially available high speed ADCs and those of say Agilent is that the latter spend a lot on R&D to design the best custom high speed ADC specific for the job. They can, because they are going to sell many in their instruments.When choosing an ADC spend some time reading on its possible errors. Flash architectures can suffer internally from metastability issues resulting in what's called sparkle codes. Some data sheets display a Bit-Error-Rate, which could be used to indicate the chance for an erroneous output code. For more information about those subjects I can recommend theData Converter Handbook by Analog Devices

author: gamozo
author_rank: Regular Contributor
timestamp: August 16, 2013, 03:39:04 pm
content: Thanks for all the advice guys!I'm currently looking at the Agilent InfiniiVision 2000 or 4000 series scopes. My budget is about 1-2k for low-end gear, however 4-5k for high-end stuff like Agilent (I'm okay shelling out more money for good quality gear). I really love the update rates on the InfiniiVision scopes, however they do have really low amounts of storage which is not great for my DSP stuff... ugh.-B

author: Lukas
author_rank: Frequent Contributor
timestamp: August 16, 2013, 04:25:11 pm
content: Quote from: Christe4nM on August 16, 2013, 12:23:28 pmThere are ways to get around this:- Pipelining: The first stage only digitizes 4 bits, the error voltage is amplified an digitized by another 4 bit adc. You need only 2x16=32 comparators- Folding: By placing a folder circuit in front of the ADC you can reuse some of the comparators.http://enpub.fulton.asu.edu/jalali/week12.pdf

author: Christe4nM
author_rank: Unknown
timestamp: August 18, 2013, 12:30:43 pm
content: Quote from: Lukas on August 16, 2013, 04:25:11 pmThanks for the supplemental comments and that lecture note. The folding technique is new to me. I knew about pipelining already, but AFAIK pipelined ADCs only go up to about 100 MSPS. At the speeds the TS requires, flash is basically the only option, and you'd probably need to interleave multiple ADCs too. Again, that is as far as I know, so correct me if I'm wrong.