So, I've been looking at the timing requirements for DDR SDRAM. Given the nature of the 100+MHz frequency domains, I'm starting to think a tiered structure with connecting pins just isn't going to work. So, back to a single card with DDR SDRAM, an FPGA, and the analog conversion equipment I'm working with. Oh well. I was hoping to avoid having to redesign my board to switch ADC and DAC hardware. The DDR I've considered building onto the card from the beginning simply because of the strict timing requirements.
Now, a longer term idea (for the heck of it) is ordering enough samples from Analog to put together a full wireless transciever interface. Just a thought, they do have parts for the whole datapath.
Now, for my NEXT trick...
Analog has a few good references online, for free, for DSP.
The Scientist & Engineer's Guide to Digital Signal Processing
Mixed Signal and DSP Design Techniques
They might be a bit Analog specific, but they're general enough and deep enough to get people going. The first one's over 650 pages printed, and I haven't looked at the second yet.