# Doppler Cone: What exactly is it?

I'm trying to understand Synthetic Aperture Radar (SAR). It appears that it makes use of what's called a "Doppler cone". I understand Doppler frequency shifts of light, but I'm not sure what the cone is. It seems like it's some kind of locus, but I can't exactly tell for what. Does anyone have the answer?

• Welcome Adil to Physics SE. A google search on "Doppler cone" provides an impressive list of results and nice pictures, are none of them satisfying?
– user130529
Dec 10 '16 at 14:33
• Tried that. They show how it's used, not what it is. So yes, they're unsatisfying. Dec 10 '16 at 15:00
• From page 9 in this paper: The Doppler cone has its axis in flight direction and its corner at the antennas phase center, the cone angle $\alpha$ is related to the radial velocity by $v_r = -V \cos \alpha$ (see definitions page 4). I'm afraid I won't be able to help you more.
– user130529
Dec 10 '16 at 15:24
• @Adil SAR radar is not that hard but you have to visualize it and analyze it to undestand first the basics (which starts with the cross range measurement done by synthesizing a measurement along the flight direction, using google Doppler shift as function of distance ahead or behind). Get a good book on radar and it'll have a SAR section. The Doppler cone are the iOS-Doppler curves. Too hat to explain in words only, and probably worse in a figures only presentation Dec 11 '16 at 7:16