Prior to the availability of the Beagle Bone Black, my basic approach was to use 2"x2" boards with PIC microcontrollers and a USB interface. In some of the posts there are references to a Prj114. This was a simple ADF4351 with PIC control interface. All together it costs about $30 (depending on how you count the PCB cost). It uses the Analog Devices reference design as a starting point. You can see the pads were not pulled out on the QFN part which caused me a great deal of trouble. It is still useful as a quick and flexible standalone source.
|Simple synthesizer using a PIC and ADF4351|