3 ms·

I suspect that a little bit of modulation cleverness goes a long way towards eliminating crosstalk.

dogma1138 11y ago
Not sure if you look at military applications then when a group of aircraft will fly in formation only 1 of them would have the radar on in active scan mode and the data is usually going to be shared over the data link. With phase shift due to movement and the uncertainty of how many cars are there around you modulation might not be enough to prevent cross talk.
- jjoonathan 11y ago
  Yes, overload is real, you can never eliminate crosstalk only suppress it, and degenerate cases will probably pop up as the tehcnology scales. But coming to a compromise that allows every car to generate a map of the road should easily be possible. Well, "easily" in the technological sense, perhaps not the political sense. For military applications it's more useful to have one radar at high range/power than to have n radars at low range/power, while it's just the opposite for civilian lidar applications. So I don't see military radar SOP as evidence that this is inherently difficult.
- Symmetry 11y ago
  Do they still do that? If so it's because they don't want to have frequency agility turned on all the time so potential adversaries get less opportunity to figure out the relevant algorithms. The degree by which radars adjust their pulse frequencies is way larger than the doppler shift of anything you're likely to run into traveling in the atmosphere. You will occasionally have a conflict by chance but radars by their very nature have to deal with a certain amount of noise. With lidars you won't be able to adjust frequency because that's not how lasers work. Well, you can with free electron lasers but nobody is going to be putting those in lidars. But a laser is directional in a way that a laser isn't. You will occasionally get some false returns but real objects persist from scan to scan in a way that noise doesn't. I've worked with a small fleet of lidar equipped robots and lidar cross talk never caused us any problems. Sunlight on the other hand could be a big problem but automotive lidars are all rated for the outdoors.
  - Schwolop 11y ago
    Ah yes - the ol' "facing west near sunset" bug... I lost a few nights sleep to that one. :-)

Not sure if you look at military applications then when a group of aircraft will fly in formation only 1 of them would have the radar on in active scan mode and the data is usually going to be shared over the data link. With phase shift due to movement and the uncertainty of how many cars are there around you modulation might not be enough to prevent cross talk.

jjoonathan 11y ago
Yes, overload is real, you can never eliminate crosstalk only suppress it, and degenerate cases will probably pop up as the tehcnology scales. But coming to a compromise that allows every car to generate a map of the road should easily be possible. Well, "easily" in the technological sense, perhaps not the political sense. For military applications it's more useful to have one radar at high range/power than to have n radars at low range/power, while it's just the opposite for civilian lidar applications. So I don't see military radar SOP as evidence that this is inherently difficult.
Symmetry 11y ago
Do they still do that? If so it's because they don't want to have frequency agility turned on all the time so potential adversaries get less opportunity to figure out the relevant algorithms. The degree by which radars adjust their pulse frequencies is way larger than the doppler shift of anything you're likely to run into traveling in the atmosphere. You will occasionally have a conflict by chance but radars by their very nature have to deal with a certain amount of noise. With lidars you won't be able to adjust frequency because that's not how lasers work. Well, you can with free electron lasers but nobody is going to be putting those in lidars. But a laser is directional in a way that a laser isn't. You will occasionally get some false returns but real objects persist from scan to scan in a way that noise doesn't. I've worked with a small fleet of lidar equipped robots and lidar cross talk never caused us any problems. Sunlight on the other hand could be a big problem but automotive lidars are all rated for the outdoors.
- Schwolop 11y ago
  Ah yes - the ol' "facing west near sunset" bug... I lost a few nights sleep to that one. :-)