2
votes
How do "Your Speed" Signs work, and how do vehicles know when it's the sign's turn to display their speed?
These are almost certainly Doppler systems (addressing some comments). The transmitted beam, be it radar or lidar, is focussed and aimed to cover the approaching lane at a decent distance. If it's ...
- 4,259
1
vote
Accepted
Optimal frequency for penetrating 1 meter of water using radio waves?
Underwater radio transmission at VLF frequencies has been used for many years by the US Navy to send signals to submerged submarines. Wikipedia has a good article on this which will answer all your ...
- 15.3k
1
vote
can I extend the the antenna of a magnetron with a cable?
Yes, but at microwave frequencies most cable connections are lossy. So instead, a waveguide is used which is a hollow metal pipe that exhibits low losses, confines the microwaves, conducts them to ...
- 15.3k
1
vote
Can a piece of conductor be made invisible to radar by overdamping?
this can be done my matching the electromagnetic impedance of the material to that of free air. By using dissipative elements (ohmic resistance) in the material to match impedances, the radar waves ...
- 15.3k
1
vote
Radar/Lidar for detection of humans in an indoor room
Technically, there are multiple options for detecting people in rooms such as LIDAR, RADAR or Ultrasound sensors (at head level). However, it is important to also consider the ethical and professional ...
- 906
1
vote
Radar/Lidar for detection of humans in an indoor room
Any reason why you want to use radar? Why not use image processing from a visible-light camera, or even an IR camera?
Edit in response to the additional details you provided:
I have done some work on ...
1
vote
A radar that is not an OTH detection distance
No. Stating the obvious, a line of sight (LOS) system won't detect things below the horizon.
Now, if atmospheric conditions cause a waveguide effect, signals could propogate farther (and back), but ...
- 4,259
Only top scored, non community-wiki answers of a minimum length are eligible