just to stick my oar in... Quoting Brian Padalino <[EMAIL PROTECTED]> on Sun 04 Mar 2007 22:47:36 GMT:
> On 3/4/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > Oh yes! Sorry, forgot to mention that part. > > I'd like to have an ADC with 65 to 105 Msps at 16 bits. This should > > allow me to sample up to 30 or 50MHz respectively. I was inspired to > > this from the Mercury project of the HPSDR, but that project relies on > > a whole lot of other hardware, running at a total cost of some $500, > > and it still relies on USB for the interface. > > Just wondering - any reason why you want 16-bits of resolution? That > gives you ~96dB of dynamic range which is great, but do you really > need it? 12-bits should actually give you a really good amount of > dynamic range while keeping everything within budget. Even a 10-bit > solution would probably give you enough to be really good while > keeping everything on the cheap. I believe even those really > expensive Agilent or Tektronix oscilloscopes just use 8-bit > converters. this is a good idea, you will probably find that the analogue receive chain introduces so to much noise to make anything over 6 or 7 bits resolution (at best) meaningful anyway > > Maxim has a pretty decent selection of high speed ADCs. Which ones > did you have in mind that you were looking at? > > > 0 to 30MHz would allow me to sample the entire shortwave band and > > below simultaneously, so I could for example have code in place to > > automatically decode and display every data transmission taking place, > > if my CPU is up for it. Tuning would be instant; I could automagically > > jump to new transmissions in the amateur bands, or click and drag on a > > waterfall display to tune. If I can code that... > > > > The ADCs I've been looking at can apparently somehow sample > > frequencies above their sampling rate aswell. I'm not really sure how > > this works, but I don't think it's an issue I must bother with right > > now. Added value for later, I think. Right now I'm only interested in > > shortwave transmissions, but the bandwidth of the ADC could surely be > > used for other things aswell. > > Those ADCs probably have a really wide analog bandwidth and allow for > "high IF" sampling - where the desired signal is located somewhere > higher than your sample rate, but the bandwidth of the signal is much > lower than your actual sampling rate. You then sample at a lower rate > than the IF and get an "image" of that actual signal - exploiting the > aliasing instead of trying to filter it out. > you said earlier that this is a home project, do you mean you have no intention of (low volume) production? for a single board $100 is a very ambitious target. BGA packages usually need multilayer to escape the signals, and PCIe needs controlled impedance. you might find that the PCB tooling costs alone exceed your budget > > -- > > Nos > > Brian > if you can reduce your data rate so that gigE will do, it's probably worth having a look for FPGA gigE development boards with an versatile i/o header, then designing a single layer (cheap) daughter board for the ADC. otherwise you're probably best to wait for the gigE usrp. (you might have to offer to do someones washing/cooking/cleaning to get them to sell it to you for $100 :) Jon _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
