Hello,
You may be interest by this project from Tipok:
http://tipok.org.ua/node/41
It's a simplified and low cost SDR transmission interface using an FX2 USB controller
and an AD9957 modulator/DAC.
Here he's using it to create a DAB digital radio transmission using CRC mmbtools DAB
multiplexer/modulator.
Mathias
opendigitalradio.org