Questions tagged [radar]
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Aliasing in Pulse Wave Doppler/Radar
There are many pictures on the Internet showing sampling of the output wave and then showing the phenomenon of aliasing, e.g.:
But on the other hand, I find information that in the pulse (Pulse Wave ...
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What are the reflective properties for 77 GHz electromagnetic waves (automotive RADAR)?
Automotive radar uses electromagnetic waves around 77 GHz frequency. Is there some data, tables available about the reflectivity of such waves for various materials, like water, stone, people, metal ...
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- The minimum distance at which a radar can detect a target is 270 m. Determine the wavelength at which the radar operates if it emits pulses, [closed]
The minimum distance at which the radar can detect a target is 270 m. Determine the length of the waves at which the radar operates if it emits pulses, each of which contains 6,000 electromagnetic ...
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Why does radar have a much longer range than infrared sensors? (in the context of military aircraft)
In the context of military aircraft and missiles, radars often have ranges of hundreds of kilometers, while thermal infrared sensors can only barely reach 100 km in the best of circumstances. But ...
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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 ...
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Is it possible for a pulse doppler radar(full coherent) to integrate multiple pulse with different carrier frequencies (during an integration)?
Especially for digital (modern) radar?
Also is it possible (in the same configuration to integrate multiple pulses with the same carrier frequency with intrapulse modulation (each pulse has a ...
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How to calculate relative permittivity from the following chart
So basically, I was using HFSS to run some simulation on a MnZn absorber https://www.researchgate.net/figure/a-Real-and-b-imaginary-dielectric-permittivity-curves-for-RAM-based-on-MnZn-...
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Single-Antenna-Single-Pass SAR interferometry
As I understand, for elevation mapping using InSAR, one typically requires an out-of-plane baseline to create the required phase difference between images to detect objects at height. This usually ...
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How to solve for the intensity of a plane wave through an aperture
The commonly cited equations for the intensity of light intensity through an aperture express the intensity as proportional to a solution rather than absolutely equal to a value.
For example, in ...
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What is the explanation that the same material could receives and reflects EM wave signal while another absorbs?
Here is B-2 Spirit, a stealth bomber by Northrop Grumman. Another one is a depiction of a parabolic dish antenna receiver. As we knew, the B-2 is a stealth aircraft, which is not reflects the received ...
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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?
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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 ...
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Time difference of arrival between radar pulses
Consider the following geometry:
Where $\bar{s} = (s_x,s_y)$ is an object of interest, and $\bar{r_c}$ is the location of the radar.
Let the echo delay time of a radar pulse to the scene center be $...
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How distance is determined between two inertial frames in empty space using Bondi’s radar method?
I have read how Bondi’s radar method can be used between two vessels in empty space to determine their relative distance and also if their distance is increasing or decreasing.
Can Bondi's radar ...
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Is Terahertz SAR imaging of Earth possible?
The Terahertz band is at the Wavelength range of 1 mm to 100 μm, which is very good for synthetic aperture radar aka SAR since the shorter the wavelength the better angular resolution you get. ...
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Mechanisms responsible for absorption loss in the Ionosphere
I have been given a task at my university of helping with calculating some link budgets for satelites. The work I usually do limits to transmitters and receivers located within the troposphere, while ...
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What is the difference between radar cross section and intensity/amplitude?
I've been tasked with simulating a radar system, and I think I understand the problem, except I'm supposed to be providing the outputs in both radar cross section and amplitude.
What's the difference? ...
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Can radar detect electrical fields?
Can we create a radar image of electrical fields, or this is even possible?
Do we need a detector opposite the emitter or does reflection work?
(see figure.1)
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Can I track hypersonic missiles with heat sensors? [closed]
On a video, it is said that hypersonic missiles create an plasma layer that scatters radar waves, therefore hard to detect
And then, on another video, it demonstrates anti-ballistic missile system ...
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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. ...
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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 ...
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Radar pulse width, peak power and relation to maximum range
The textbook I'm using to understand radar is explaining the 'pulse width dilemma'. It says that shorter pulse widths can resolve targets that are close together; however, because there is a limit to ...
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Location of first null off boresight, in ant pattern of 2 element phased array antenna, in radians as a function of wavelength and distance?
Does it make sense that the first null off boresight of a 2-element phased array antenna, where each element is isotropic, in-phase, and separated by a distance $d$ (where $d$ is much greater than the ...
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Is there any kind of "radar" system That can detect electrical fields / electricity
I may be using improper terms here, but Is there any kind of "radar" / non-contact system That can detect electrical fields / electricity? see fig for clarification to what I'm talking about....
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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.
...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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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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 detection: 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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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