step FMCW signal generator by PLL

with a 16_divider 24GHz VCO, I want to setup a PLL to give a 2KHz step triangle frequeny FMCW. It is only an idea ,and i find it is too hard to meet the 2KHz frequency. If there are 16*2 steps in a cycle, one step is 15.625us ,there must some time to process the radar data, so lock time should less than 10us.

And phase noise performance is bad because of the large divide ratio

Anybody give me some ideas?