Questions tagged [radar]

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How to calculate the RCS (Radar Cross Section) of a sensor tag?

The equation for finding the RCS of sensor tags is given in the following paper. where $S_{21}^{tag}$ stands for the $S_{21}$ measurement taken for the tag in front of a reader. $S_{21}^{isolation}$ ...
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34 views

Speed between two cars with radar

I found a programming problem that calculated the speed between two cars as below and I would like to know how the calculation is done. It is about determining the speed of lead car. The coordinate ...
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1answer
37 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 \...
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51 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, ...
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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 ...
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180 views

Radar waves all waves not working under water

was just wondering why all waves don't work under water for? I know they work for 10 meters "but" after that they don't. Does it have anything to do with it's wavelength? Or is it just that the ...
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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 ...
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6 views

Signal's phase change requirement for benefiting from coherent integration

Maximizing the potential of coherent integration requires that the signal’s phase vary by less than 90deg over the entire integration interval. What exactly does that mean in a FMCW radar application ...
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1answer
72 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 ...
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1answer
30 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 (...
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2answers
29 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 ...
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775 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, ...
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51 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 ...
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322 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 ...
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3answers
65 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 ...
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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?
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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 ...
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561 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,...
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3answers
126 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 ...
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211 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 ...
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1k 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 ...
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2answers
83 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 ...
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1answer
28 views

reading radar / waves changing after hitting each other

Can you read a radar or any wave when it hits another wave...it changes? So say a radar wave hits another wave changing it miles away, can you get info of that hit happening miles away from the radar ...
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1answer
72 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 ...
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397 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 ...
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573 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 ...
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17 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 ...
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123 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 ...
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91 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 ...
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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 ...
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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 ...
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76 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 ...
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1answer
489 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?
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343 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 ...
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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?
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1answer
393 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 ...
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10k 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 ...
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234 views

Looking for full equation for radar cross section of corner reflector

There's a well-known formula for the RCS of a corner reflector (aka corner cube), to wit $ \sigma \varpropto \frac{L^4}{\lambda^2} $ . I've found several sources which cheerfully say "...valid for $ ...
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1answer
3k 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 ...
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2answers
109 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?
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Conjugated-Phase Matching

I am working on imaging applications of phase-conjugation in optics, in particular phase-conjugation imaging from recorded holograms. I have found several useful sources, but I cannot find a book ...
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575 views

Scale-down modeling for radar cross-section measurement

Scale-down models for targets are used for radar cross-section measurements of huge-size objects. Is there any upper limit to the scaling factor on downscale modeling as a $100~\text{m}$ length of ...
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1answer
2k views

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?
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222 views

Can natural predators detect human stealth technology?

Just a thought experiment since bats are probably not swift enough to take evasive action in the scenario described. If a cloud of bats were to encounter a B-2, or F-35, or F-117 or any of the other ...