DesignSpark files and the Gerber files, in the <VanSlyke-LTC5598xmitBVS-QEXfiles.zip> folder.  

Here is a brief description of the contents:

DacPostFilter.sch - Schematic of the audio filters that filter the I and Q signals prior to going to the LTC5598 transmitter
LTC5598xmit.sch - Schematic of the circuit that drives the LTC5598
xmit5598.pcb - PCB file of the entire LTC5598 transmitter
xmit5598.prj - DesignSpark project file of the LTC5598 transmitter
xmit5598.mop - DesignSpark intermediate output file
Gerber plots (folder) - contains the Gerber files of the xmit5598.pcb.  The board has two layers, with silkscreen on top.


basebandIQ.pdf is a pdf of the Octave code.
basebandIQ.m is the Octave code text file.