Need roughly 10ns or better ramp to drive a VCO

I'm looking for some product such as the AD9956 in an evaluation board form for quick setup. In our application we are looking to generate a ramp that can go from 0V to (8V or 10V) in less than a 10ns time period. We want to use this ramp to drive a VCO that will give us 1GHz of BW over 10ns (chirp). It sounds like a DDS might be able to give a ramp necessary to drive a VCO or it can do the chirp directly. Can the AD9956 do a ramp with these requirements? If not, what are the limits it can meet? Also might a different DDS be able to do this? Thanks, John