Questions tagged [radar]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
0
votes
1answer
16 views

Through-metal-wall Ultrasound sensor imaging?

A while ago, MIT published a paper that used a radar sensor to take a low-res image, and then they trained an AI model to convert the image into a human skeleton for through-wall human pose detection. ...
1
vote
4answers
86 views

Is there an alternative to radio waves that can go through metallic objects?

Radar can pass through materials such as paper, wood, glass, brick, and concrete, but it reflects off of metal. Is there an alternative to radar that can pass through metal substances? If not, is it ...
0
votes
0answers
9 views

Expression for covariance matrix as a function of distance

I am studying a tracking problem in which the measurement noise, assumed to be Gaussian, increases as a function of the distance to the target. I am seeking an expression for the covariance of this ...
0
votes
0answers
18 views

Doubt in radar question

This is a question(2.25) from introduction to radar systems by Merrill Skolnik 3rd edition. Plot the single-scan probability of detection as function of range, assuming a constant cross-section target ...
1
vote
1answer
71 views

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 ...
0
votes
2answers
33 views

Radar lobes vs forever propagating waves

I'm trying to learn some more about radar and I'm confused about "lobes". My understanding of EM radiation is that it radiates forever or until something physical blocks it, but directional ...
0
votes
0answers
11 views

Required Optical Fiber Bandwidth from (Radar) Signal Bandwidth

I have a radar background and am currently struggling to understand even basic photonics because I feel the terms used are quite similar, but not identical and additionally very confusing. Let's say I ...
3
votes
2answers
1k views

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 ...
0
votes
0answers
24 views

How is the synthetic aperture of a radar done?

In the case of SAR (synthetic aperture radar), the Doppler effect is used to simulate an antenna (syntetic) whose resolution is better. What I would like to know is how this is done in detail, what ...
0
votes
0answers
17 views

How to compute the signal propagation loss from each position in a map to one particular receiver location?

I have read up on signal propagation models and RF simulation software. Most software I found computes the path loss for a transmitter at a particular position to each position in the map. I now want ...
0
votes
0answers
52 views

Doppler effect and Lorentz transformation

At time $t_0 = 0$ someone on earth sends a (frequency modulated) signal to a spacecraft, which is at distance $R$ and moves with speed $v \geqslant 0$ along the $x$-axis. Suppose the signal is ...
0
votes
1answer
16 views

FMCW radar scattering direction from a special case of a rough dielectric surface

I have some misunderstandings about radar backscatter from rough dielectric surfaces and was hoping somebody could enlighten me. I have one specific question first concerning a thought experiment. A ...
0
votes
0answers
7 views

Are rough dielectric surfaces (for purposes of scattering) always a collection of specular surfaces?

When an EM-wave (e.g. radar $\lambda$=1cm) is incident on an extended specular surface (e.g. glass), the angular distribution of the scattering is a delta-function. That is to say, angle of reflection ...
-1
votes
1answer
37 views

Will a sheet of carbon atoms reflect radio waves?

I am working out some details in a SciFi novel. I'm thinking of having spec ops who would use a device that could manipulate carbon atoms to form and maintain large, rigid, one-atom thick carbon ...
0
votes
0answers
41 views

What is the radar cross-section of a Romanesco broccoli?

The Romanesco broccoli is an interesting vegetable that exhibits a fractal pattern on its surface : Image link Regarding physics, I was wondering what is the radar cross-section of this pattern ? Can ...
1
vote
2answers
50 views

How did early radar determine range/ distance precisely?

Wikipedia talks about precise timing of the returned radar pulse, with an animation of a clock. But they didn't have atomic clocks and such before or during WWII. So how did they determine distances ...
0
votes
1answer
31 views

Radar Wave Reflection — How can we justify coherent radar?

How can we model a radar wave's reflection from a target? Will the phase of the return be different from the signal that gets sent out? For instance, suppose our radar was transmitting the following ...
0
votes
1answer
72 views

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 \...
0
votes
1answer
55 views

Is Sentinel able to obtain wave spectrum by interferometric Data?

I have recently read many articles on recovering wave spectrum from the AT-INSAR image spectrum (through interferometric images). However, it is not clear to me whether Sentinel is a viable option, ...
0
votes
2answers
286 views

Painting a vehicle black to avoid radar detecion: a bad idea?

A lot of people on the Radar Detector & Laser Jammer Forum are trying to paint their cars in the deepest black to avoid getting a speed ticket by making their vehicle stealthier for incoming radar ...
1
vote
3answers
2k views

Why does this radar speed sign show a decreasing speed, despite the fact that I'm accelerating? [closed]

Everyday when I'm going back home from college, I pass by this big radar speed sign and I've noticed that it does a peculiar thing. The sign is placed on a downward slope of the street. So say I'm ...
0
votes
1answer
155 views

Why aren't extremely-low-frequency (ELF) radio waves used for underwater radar?

Since extremely-low-frequency radio waves are used by submarines for some simple, low-transmission-rate communications, why can't those same wavelengths be used for submarine radar? It may not be ...
1
vote
1answer
38 views

Loss of beam power over astronomical distances

pardon my choice of words, but English isn't my native language, so I might use the wrong terms at some places. Beside this, I do have a hypothetical situation which might be a bit off reality (...
1
vote
2answers
51 views

Why does a sonar or radar's frequency correlate with its resolution?

A sonar's (or radar's) frequency determines its limit on the smallest size that it can detect and its resolution. I've heard that it's due to aliasing, if so, please explain the reason behind it a ...
0
votes
0answers
863 views

Radar Vs. Sonar

What is the true difference between radar and sonar? My understanding is that radar uses a reflected EM wave, while sonar uses a compression (shock wave) of the material it's in. (It compresses water, ...
-1
votes
1answer
100 views

Can radar detect dumb bombs in freefall mode? [closed]

Can gravity bombs dropped from an aircraft be detected by radar and intercepted with a missile to prevent detonation on ground impact? Is there currently such a system? Edit: Its a military/defence ...
1
vote
2answers
367 views

Why can't LIDAR be implemented with traditional antennae?

In robotics, LIDAR and RADAR are both used for obstacle detection. The data they produce are very similar, but they do have different qualities (LIDAR is more precise but less robust). There are many ...
2
votes
3answers
244 views

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 ...
0
votes
2answers
1k views

Does radar affect magnetism?

Does radar affect magnetism? Let's say I have two magnets, one is suspending the other. Would radar affect the magnetic field?
2
votes
0answers
33 views

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 ...
0
votes
3answers
840 views

Chaff-RF Relationship?

What is the relationship between chaff length and the frequency it is meant to interfere with? I've read that specific lengths of chaff are more effective as a countermeasure for specific frequencies,...
1
vote
3answers
222 views

L-band for search radars?

I'm making my way through the Linesman-related section's of Gough's Watching the Skies. Linesman was developed to counter the carcinotron jammer. The main solution was the Type 85, which had 12 ...
0
votes
1answer
232 views

Does Radar detect objects or has point cloud

Many times in literature I read that Radar is used to detect objects. How does this work? Are reflections from objects with Radar not point reflections? And how does Radar know that all reflections ...
1
vote
1answer
2k views

Radar: frequency and target size

I am wondering if there is a general rule of thumb in the radar world for what frequency you should pick to detect targets of a certain size. For instance, if one had two radars set up - one for ...
1
vote
2answers
124 views

How does increasing conductivity increases radar cross section?

This is for the context of radar detection. I am trying to figure out exactly why increasing the conductivity of a metallic object increases its radar cross section. I've been directed to looking at ...
1
vote
1answer
80 views

When using radar in space to find asteroids is it helpful to know the distance? Or do you just need the direction?

Couldn't they just send out the largest sounding pulse in a given direction that they could safely generate, and if there is anything in that direction no matter if it's by Jupiter or pluto as long as ...
0
votes
1answer
441 views

Bistatic radar equation for moving objects

From my understanding, and correct me if I'm wrong, the bistatic radar equation assumes that the transmitter and the receiver are separated by a distance $L$, and that the transmitter and receiver are ...
0
votes
1answer
22 views

Is there a way to recalculate radar detection range given the old and new probability of detection and false alarm?

I'm reading through some radar books and I'm trying to find out if there's an easy method or equation to recalculate radar detection range given only the original radar detection range, original ...
1
vote
1answer
151 views

Why is my reasoning to derive the bistatic radar equation wrong?

The ideal effective antenna aperture is calculated from $A_{eff}=G\lambda^2/4\pi$, G being the antenna gain. Why is it that in a bistatic radar setup with a transmitter and receiver fixed on the ...
1
vote
0answers
108 views

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 ...
2
votes
0answers
495 views

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 ...
1
vote
2answers
5k views

Do radio waves interact with electrical wiring?

AFAIK radio waves can be influenced by magnetic fields (when not traveling through a vacuum). Electrical wires create a magnetic field perpendicular to the length of the wire, as a function of the ...
5
votes
0answers
101 views

What happens to a radar signal when it meets with a superconductor? [duplicate]

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 ...
0
votes
1answer
687 views

What exactly is an “instrumentation radar”? [closed]

I am coming across this term "instrumentation radar" without exactly defining it but with adjectives like high performance, mono pulse etc. But what exactly is an instrumentation radar?
0
votes
1answer
353 views

Why would a sweeping LIDAR or RADAR beam not produce an artificial Doppler shift?

Assuming a bi-static Radar or LIDAR with a stationary transmitter and a stationary target and a stationary receiver, with a sweeping RADAR/LIDAR beam reflecting off a stationary target: Why would the ...
2
votes
0answers
61 views

Wavelength, frequency, and radars [closed]

I'm doing a high school paper on the effects of frequency alterations on a radar image. Can someone recommend a book which I can use?
7
votes
1answer
441 views

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 ...
18
votes
2answers
11k views

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 ...
1
vote
1answer
4k views

Simple explanation of Coherent integration radar

I have a physics background, and I'm reading some physics data analysis papers where they keep throwing around the term coherent integration. I've done the google search, but the best answer I could ...
1
vote
2answers
110 views

Radars on Space Ships

If a radar (say, an x-band radar similar in size to that of a modern fighter aircraft) was carried by a spaceship, would the radar have a greater range in vacuum of space than it has in atmosphere?