If you're interested in software, you might be wondering how much software I have for this project, or where you can check it out. I've just put some code up on GitHub, you can check it out by following the sidebar link.
Truth be told, there isn't much software right now.
Part of the reason for this is that I'm focussing on the relatively tricky microwave electronics first, and getting the RF hardware platform working. Another reason is that some people (Greg Charvat, for example) have already created some fantastic signal processing software tools and shared their contributions with the world.
I've put up my quick SPI test code, using an Arduino to drive a Microchip SPI DAC to generate a triange-wave modulation signal (this is amplified, as previously discussed, into an 0-10V signal.) However, this was just a quick experiment and it is unlikely that the finished product will use an ATmega328 microcontroller or Arduino-compatible bootloader. I'll continue to share any quick little software tests, tools or scripts as they come along.
Another thing I'm currently working on is to take the MATLAB signal processing and visualisation scripts provided by Greg Charvat and the MIT/Lincoln Lab folks, and to tweak these for the best match to my hardware characteristics - and to replace the use of MATLAB with free software tools, since MATLAB isn't really the cheapest, most accessible choice. As work progresses, I'll continue to share these changes and new code that is written.