Questions tagged [radar]
71 questions
19
votes
2 answers
How do they measure the rotational speed of cricket balls?
The 2013 Ashes series (a cricket thing between England and Australia) are underway as of today and it seems they have a new (to me) gimmick. It appears that they are now able to measure almost instantaneously (within a few seconds) the rotational…
Řídící
- 6,847
12
votes
3 answers
Avoiding radar detection using active noise control instead of a stealth fuselage
was reading about different stealth technologies used by modern aircrafts to avoid radar detection.
Wouldn't it be easier to have a receiver on the airplane listening on the radar frequencies and then re-transmit that same signal but phase shifted…
Henry Skoglund
- 131
8
votes
1 answer
Is radar-style 'pulse coding' (stretch, amplify, interact, and then compress) used in the optical domain?
Chirped Pulse Amplification (CPA) is an optics technique for producing short laser pulses at intensities which are high enough that the gain medium would destroy itself through nonlinear phenomena like self-focusing and laser filamentation if it…
Emilio Pisanty
- 137,480
6
votes
3 answers
Why can we not measure the distance to the Sun directly using Radar?
My question is specifically WHY CAN WE NOT USE Radar to measure the distance to the Sun? What is the reason for that?
Sorry if this is a lame question, I'm not an expert on these things and just occurred to me why not use radar to measure the…
Andy Zee
- 61
5
votes
0 answers
What happens to a radar signal when it meets with a superconductor?
A radar system has a transmitter that emits radio waves called a radar signal, consisting of electromagnetic radiation. What happens when it meets with a strong superconductor, considering the fact that a superconductor expels magnetic fields. Will…
Fasasi Tosin
- 51
- 3
4
votes
2 answers
Can low lying clouds increase the distance of the radar reach from 18 to 120 km?
I have seen an article (sorry its Russian) claiming that low lying clouds have increased the distance of the radar reach from the normal 18 km till as far as 120 km. This allowed the military ship to be detected and sunk.
The source claims that the…
Nightrider
- 419
4
votes
1 answer
Does weather obstruct microwaves and radiowaves?
I read an article ('How airplanes use radar' at Bright Hub.com) that stated that airplanes use radio waves for communication because they aren't obstructed by weather.
Is this true?
DarkLightA
- 1,442
3
votes
2 answers
LIDAR vs. RADAR
Our TV news today said the cops have switched from radar to lidar because it is more accurate in fog. But isn't light absorbed by fog more than radar frequencies?
WGroleau
- 369
3
votes
1 answer
Why do pulsed signals have a bandwidth but continuous wave signals do not?
A continuous wave signal of 'f' kHz will appear on a receiver plot tuned in at f kHz and nothing else, ie it is 1 Hz wide. However, apparently this is not the case with pulsed signals and I'm struggling to understand why. Apparently, even if the…
VeryCommonName
- 289
3
votes
3 answers
Why do sensors that emit higher frequency signals give more accurate data?
I am doing a technical presentation about RADAR and LiDAR. I understand that LiDAR is several times more accurate and capable of producing really detailed 3-D maps of their surroundings, while RADARs tend to lag behind in accuracy.
Several sources…
2
votes
1 answer
Why do metallic objects reflect radar?
We learn that EM waves cause the electrons in a conductor to move around. For example, air to ground radar shows the ocean as having few returns compared to land. Water molecules absorb the energy. Doesn't the induced motion of electrons in the…
aquagremlin
- 1,729
2
votes
1 answer
Doppler Effect and Radar Sensors
Radar sensors make use of the Doppler effect to measure the radial velocity of an object.
The radar's Tx antennas emit an electromagnetic wave which travels to the moving objects, is reflected and the radar's Rx antennas detect the incident…
Merlin1896
- 769
2
votes
2 answers
Energy in radar equation
In the book Skolnik, Introduction to Radar Systems, ed. 2, pag. 52 (sec. Transmitter Power) the radar equation in its simplest form is initially cited:
$$R_{\max}=\left[\frac{P_t G A_e \sigma }{(4 \pi )^2 S_{\min}} \right]^{1/4}$$
where $P_t$ is the…
Nameless
- 107
2
votes
0 answers
Radar Antenna Quantity and functional performance
Millimeter wave radar SoC (system on a chip) are evolving from 4 to 72 antennas on a single chip. Is there a simple (ELI5) explanation as to why 72 antennas (vs 4) are desirable?
My intuition says it improves either / both resolution and…
gatorback
- 121
2
votes
0 answers
Doppler radar electric field expressions
Consider the right handed coordinate system $(x,y,z)$ in which a stationnary radar is positioned at the origin and a metallic plate (initial position $z_0$) that is moving along the $z$ axis with speed $v$ (the plate is perpendicular to the $z$…
Corvinus
- 109