While reading the datasheet of the ADF4159 I came upon a section describing how to create an FMCW ramp with FSK superimposed to "enable unambiguous (distance and velocity) multitarget detection". While this sounds like a wonderful radar technique, I do not understand how it works. There does not seem to be a lot of online documentation on it.
Page of the section: 29
I am especially confused with the picture they provide of the frequency domain:
What are the dashed lines supposed represent? Why does each step seem so "uneven" with each other? What exactly is the smaller dimension arrows/line measuring?
I already understand the concepts that drive FMCW radar using a linear sawtooth or triangular ramp, so could anybody explain how LFM-FSK radar works, possibly in a visual way? How exactly does it interact with the target? What does it look like on the frequency and/or time domain? And is this method of measurement worthwhile (in terms of complexity vs functionality) compared to other alternatives?
I simply seek knowledge here, I don't plan to try to detect missiles anytime soon :)