What is Radar: Definition and 155 Discussions

Radar (properly R.A.D.A.R. or RADAR, for Radio Detection and Ranging) is a detection system that uses radio waves to determine the distance (range), angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the object(s). Radio waves (pulsed or continuous) from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed.
Radar was developed secretly for military use by several nations in the period before and during World War II. A key development was the cavity magnetron in the United Kingdom, which allowed the creation of relatively small systems with sub-meter resolution. The term RADAR was coined in 1940 by the United States Navy as an acronym for "radio detection and ranging". The term radar has since entered English and other languages as a common noun, losing all capitalization. During RAF RADAR courses in 1954/5 at Yatesbury Training Camp "radio azimuth direction and ranging" was suggested. The modern uses of radar are highly diverse, including air and terrestrial traffic control, radar astronomy, air-defense systems, antimissile systems, marine radars to locate landmarks and other ships, aircraft anticollision systems, ocean surveillance systems, outer space surveillance and rendezvous systems, meteorological precipitation monitoring, altimetry and flight control systems, guided missile target locating systems, self-driving cars, and ground-penetrating radar for geological observations. High tech radar systems are associated with digital signal processing, machine learning and are capable of extracting useful information from very high noise levels.
Other systems similar to radar make use of other parts of the electromagnetic spectrum. One example is LIDAR, which uses predominantly infrared light from lasers rather than radio waves. With the emergence of driverless vehicles, radar is expected to assist the automated platform to monitor its environment, thus preventing unwanted incidents.

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  1. Tracy Rose

    Can We Create a Visual Radio Camera?

    Radio is usually used as RADAR blips but has anyone tried to make a visual DSLR type camera and producing images? I'm not talking about a waveform showing the frequency placement but a real image of objects the radio bounced off of? We have tons of radio stations as the 'light' source here in...
  2. O

    Radar antenna: measuring H or E?

    Hi there, Maybe this is a stupid question. Maybe not. I want to make a statement in my thesis that says that all radar antennas on satellites derive the EM field by: receiving the time-varying H field, and from the induced current derive the EM field. Am I correct in saying that? Or are there...
  3. S

    Radar systems in cars - health hazard?

    Many modern cars now employ radar systems for intelligent cruise control as well as blind spot monitoring. Can the radar waves that are reflected back to the vehicle for these applications pose a health hazard to the vehicle occupants?
  4. D

    Can Coax Handle 10 GHz RADAR Power?

    I am under the impression that a person might be able to use a short (10 foot) piece of coax to run 10 GHz microwave RADAR energy down instead of using WR90 waveguide. Is this even remotely possible? Is there any such coax that can handle the RF peak pulse or AVG power form an old RADAR set...
  5. G

    Question about RF absorbers and radar

    Hi everyone , new to forum, but not new to forums. I am a radar detector hobbyist and have some knowledge of how radar works. Specifically and to be on point and productive, here's my question(s): First, are there any materials readily available to general consumers that will readily absorb...
  6. J

    Calculating Radar Cross Section for a Spherical Object in GHz Frequency

    How do I calculate radar cross section given the diameter of a spherical object and the radar's frequency in GHz? Thanks
  7. M

    Radar Cross Section (RCS) problem

    As we know RCS is measure of how detectable an object is with a radar. But I don't understand one thing. If we take a sphere as an example, we can see that RCS is the largest in forward direction (forward scattering). If the sphere is to big (radius>>lambda), still this forward scattering is...
  8. Jorrie

    Radar distance on DrGreg's Rindler chart?

    In an old (2008) thread, DrGreg posted this transformation from a Minkowski chart to a Rindler chart He also wrote: My question: using these photon worldlines, does a two-way radar measurement give a valid radar distance between two points in the Rindler frame, as per this zoomed...
  9. U

    What is the maximum distance a radar can detect objects on the Earth's surface?

    Homework Statement A radar has power 1kW and is operating at a frequency of 10GHz. It is located on a mountain top of height 500m. The maximum distance upto which it can detect object located on the surface of the earth(Radius of Earth = 6.4*10^6 m) is Homework Equations The Attempt at...
  10. A

    Transparent Materials to Radar between 4-8 GHz

    If I am using radar to determine the distance of an object from my transmission source by reflecting my radio waves off of the surface of the object and recording the time at which they return and, I want to encase my detector to protect it from the elements, how do I select the material with...
  11. G

    Electrical Building an Electronics Project: Radar Device Ideas

    Hi all, For an applied electronics class I'm currently taking, we have to come up with and build an electronics project of our choosing from scratch. I think it would be cool to build some sort of radar device. I have been looking into phased array radars, radar speed detectors, etc., but a lot...
  12. WannabeNewton

    Radar distance Rindler observer

    Hey guys. I have a question regarding exercise 6.5 in MTW ("Radar Distance Indicator"). The exercise asks the following: http://postimg.org/image/lkn2oujc5/; I did the problem several different ways and I always end up at the same final equation relating ##L_0## to ##L##, an equation which...
  13. MarkFL

    MHB Rate of Change of Plane's Distance from Radar Station - Gina's Question

    Here is the question: I have posted a link there to this topic so the OP can see my work.
  14. J

    Calculating Speed with a Radar Gun: Exploring Doppler Shifts

    Radar Guns are used to measure the speed of a moving object. The wave it emits experiences two Doppler shifts. How does the radar gun then use the difference in frequency of the initial wave it emits and the frequency of the final wave it receives to calculate the speed of the object...
  15. Y

    Is ruler or radar measurement more accurate in defining length in relativity?

    Ideal rulers in relativity are generally assumed to be consistent with radar measurements. The modern definition of the unit of length is defined in terms of the speed of light. However, here is an a simple example where a ruler measurement does no coincide with the radar measurement. To...
  16. marellasunny

    Radar as range detector between cars-static sender vs dynamic sender

    Say I have a radar transmitter on a car,used to detect its distance from a car in front of it by measuring the doppler shift on the reflected wave. i.e Car 1 is the source, its wave gets reflected by Car 2 in front of it. My book splits the problem of calculating the Doppler shift by computing...
  17. J

    What materials are transparent to radar? Weatherproofing a radar gun

    I’m currently working a project to produce a roadside speed camera which displays vehicle speed to drivers to improve speed awareness. A Doppler radar gun operating at 24.1GHz (1.24cm) is being used as the source and detector. There is a weather tight plastic box (opaque, at least to visible...
  18. M

    Conditions to be Picked Up By Radar

    What are the conditions that must be satisfied for an object to be picked up by radar? For example, what size must objects be in order to be picked up? Do they need to have certain physical/chemical properties in order to be picked up? Can non-metallic or organic substances like humans be...
  19. C

    Looking for An Introduction to Radar Text

    I'm in the market for an intro book covering airborne and ground radar fundamentals. The following two books are the top sellers on Amazon, but top seller doesn't mean best quality (Stewart Calculus, etc.). An Introduction to Airborne Radar by Stimson Principles of Modern Radar: Basic...
  20. Saitama

    Relating Path Difference and Intensity in Radar Signals

    Homework Statement Homework Equations The Attempt at a Solution The path difference between the two rays being received by antenna is ##h/cos(\alpha)## but how to relate the path difference with the intensity?
  21. S

    Advice on building very primitive phased array radar

    Hi, I am interested in building a very primitive phased array radar for short ranges(1m to 100m). I thought it's possible to use a simple 2.4GHz RF ASK transmitter, and by just sending a single '1' bit I could generate a pulse and then use a simple RF receiver for that frequency and analyze the...
  22. A

    Lorentz, simultan, radar finds dust grain, inconsistencies

    Hi all, Here is the problem. I want to try to do some calculations with seeing how much time a relativistic ship has before it can dodge a dust grain. I am having some trouble applying the Lorentz Contraction Equations to get consistent results. Take two frames, the coordinates of the...
  23. I

    Help with Doppler effect radar question.

    Can any of you help. I am trying to fight a speeding ticket with a written declaration. To be honest I feel it was so unfair I was going with the speed of traffic and marked me as going 6mph more. I am sending the court explaining how I believe this was wrong and a radar error. Taking Physics...
  24. G

    Phased Array Radar: Scanning Volumes of Space Accurately Per Second

    Let's say I want to use a phased array detector on a satellite to detect other objects in space. The radar would need to be able to detect objects .5cm or larger, and would have to get an accurate read on their position (within 10-15 m). From there, the goal would be to maximize the volume of...
  25. W

    What's the Meaning Behind the Fish Post on this Forum?

    I am a new member at this forum. You can call me WY. I picked this name because it seems I have lots of questions. I was looking for a forum that can ask and answer various questions of different sorts to those interested in solving answers. I’ve posted mostly at other forums such as new...
  26. A

    Blimps & Radar: Do They Show Up on Radar?

    Do blimps show up on radar? And if so, could somebody explain why? Is it the material they are made from (mylar/nylon)? Is it that their low density somehow gives an odd reflection?
  27. N

    UWB (Impulse) radar advantages over Pulsed radar

    Hi, I was wondering what the advantages are of using an Ultra Wide-Band (UWB) radar system (also known as impulse radar) where you transmit an extremely small pulse (sub-nanosecond), and hence a very large bandwidth, over conventional radar that use continuous waves or larger pulse widths...
  28. W

    Angle Estimation in Non-Doppler Radar Imaging: Exploring the Role of Phase

    Hey all, I am brand new to the world of signal processing and radar, but I am trying to simulate a non-doppler imaging radar using pulses. I understand most of the concepts, including steering vectors and measuring distance by the time delay of a radar pulse. I am using a stationary antenna...
  29. L

    Doppler effect for radar gun

    Homework Statement Radar is used to measure the speed of passing vehicles. A stationary radar gun emits EM radiation, a proportion of which is reflected from the target vehicle which is moving away from the gun at 'u' ms^-1. a)State the frequency at the target vehicle (f.tar) in terms of...
  30. V

    Simple continuous tracking radar system with cantenna - how to get ranging info?

    Simple continuous tracking radar system with cantenna We are in need of a simple radar target tracking signal processing method. It's to be very short range, less than 5 meters. It needs to track a single target that can be moving or stationary at any time. We are using 2.4 GHz ISM band...
  31. 4

    Radar Question About Doppler Frequency

    Homework Statement How to find the radar resolution? Homework Equations Doppler frequency = 2v/wavelength f = 2B R = ct/2 The Attempt at a Solution I don't know how to take the length of the aircraft into consideration. I only know how to calculate the doppler frequency but not the range...
  32. V

    Can Radar Be Used to Map Distant Planets?

    Would it be possible to use a very powerful k band radar signal to bounce off one of the rocky planets discovered orbiting other stars? If that is possible could we use it to build a radar map of the planet?
  33. C

    How does a radar gun determine velocity?

    Homework Statement Radar guns emit radio waves. The radar gun measures the beat frequency between the returning waves. How does the radar gun determine velocity? A. By measuring beat frequency between two consecutive reflected waves. B. By measuring the beat frequency between a wave...
  34. C

    Acoustic radar project for students

    I came across an article in American Journal of Physics recently that describes how to build an acoustic radar by transmitting a carrier modulated with pseudo-noise code through a speaker and simultaneously receiving the reflection with a directional microphone. One then does some signal...
  35. C

    Projection of meteorology radar images onto a sphere

    Hello everybody, I am working on a project for merging the images of multiple meteorology radars covering a large area. I would like to project each of the images onto a spherical surface and merge them. Do you know if there is a piece of software that can help me with that? I can develop in...
  36. H

    Radar Doppler Effect: What Does the "V" Stand For?

    in the equation at: http://en.wikipedia.org/wiki/Radar#Doppler_effect what does the v stand for? it is not explained, only vobs and vs are explained. Thanks.
  37. K

    Pulse doppler radar: resolution of speed measurements

    Homework Statement Pulse radar: Parameters: Carrier frequency: 5.3*10^9 Hz Pulse length: 20*10^-6s PRF: 30*10^6Hz Homework Equations The question is this: "100 pulses are reflected from a moving target and received by the radar. -What is the resolution of a speed...
  38. J

    What is the purpose and design of wire mesh on radar antennas?

    Hi, I havn't posted for quite some time yet I have been reading through from time to time. I would like to ask about Radars. I wish to be able to look at a radar antena and be able to say as possible. Such as frequency ranges from the antenna size etc... Does the size of the 'Ball' in which...
  39. T

    Radar received field no spreading

    Consider a received radar signal of the form s(t) = \frac{p e^{i 2 \pi f ( \frac{2 R(t)}{c} )}}{ [4 \pi R(t)]^2} where p is the reflectivity value, f is the carrier frequency, and R(t) is the range. In some cases I have seen this written as s(t) = p e^{ i 2 \pi f ( \frac{2 R(t)}{c} )}...
  40. M

    Radar Camera for Large Format Photography

    Large Format Photograph Machines usually uses 8x10 inches size negative. Can I make a radar large format camera with using similar or bigger size plate as antenna and when transmitter was a cw radio transmitter ? I know only need of mixing transmitted to received. If this does not work , can...
  41. G

    Solar panels and radar in Earth's orbit

    Hello, I am planning to design, and maybe build, a CubeSat, or a satellite that is 10cm x 10cm x 10cm, and weighs less than about 1.5 kg. I am looking to have 6 solar panels on the cube, one on each face, and also have a full 360º in all directions radar, along with a GPS and some radio...
  42. M

    Electrical Build a DIY Doppler Radar for Short-Range Tracking: Tips and Techniques

    I'd like to know how to build a short-rang (maybe 30-100 ft) Doppler radar. I will use the radar to pinpoint any object it sees on a map. This radar will be used with a PC or iPhone, so the unit does not make any calculations whatsoever. Also, I'd like the unit to be as small as possible.
  43. Q

    Solving the Car's Speed: Radar Velocity and Reflection

    Homework Statement A car is driving west and a patrol officer is driving east at 23.50 m/s. The officer's radar gun indicates that the car is speeding. If the radar gun sends out a frequency of 24.15GHz and receives a reflected signal of 24.20GHz, what is the velocity of the car? (Assume radar...
  44. E

    Relative Motion- Airplane vs radar station and tracking the displacement

    Relative Motion-- Airplane vs radar station and tracking the displacement In Figure 4-49, a radar station detects an airplane approaching directly from the east. At first observation, the airplane is at distance d1 = 340 m from the station and at angle θ1 = 34° above the horizon. The airplane...
  45. C

    Can radar detect flying animal?

    Hello, Chitose wonder chick here. It's been a while since last time I post my question here. right now I'm working on my new novel and need little help about radar. ........... Can radar that scan through sky detect flying animal? (in my case is 4 meter dragon) I wonder, If it can...
  46. T

    Would a Faraday cage block all types of radar?

    Would a faraday cage block all types of radar?
  47. P

    A descriptive picture of radar simultaneity

    I'm sure someone else must have come up with this (the description in the third paragraph), but I haven't seen it. Briefly, for those not familiar with it, radar simultaneity generalizes Einstein's simultaneity convention directly to arbitrarility accelerating observer. Dalsepam has posted a...
  48. A

    Related Rates: Solving Radar Station Angle Change Problem

    Homework Statement At a certain moment, a plane passes directly above a radar station at an altitude of 3 miles at a speed of 300 mph. Suppose that the line through the radar station and the plane makes an angle θ with the horizontal. How fast is θ changing 50 min after the plane passes over...
  49. P

    How can radar data be used to calculate acceleration?

    It is very easy to establish distance and velocity by measuring the roundtrip time of a radar signal that is reflected by a moving observer. However does anybody have the formulas to determine the acceleration which should be describable in terms of an increase or decrease of the roundtrip...
  50. E

    Getting Extinction cross section from Radar cross section using HFSS

    Hi, Has anyone tried using the HFSS software to get the extinction cross section of a particle? I've been told that the extinction cross section of a particle is the imaginary part of the radar cross section in forward direction, so I did exactly what the RCS tutorial from HFSS did, except...
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