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A beginner's guide to RADAR

Discussion in 'Modern Warfare' started by jagjitnatt, Jun 4, 2010.

  1. Devianz

    Devianz 2nd Lieutant FULL MEMBER

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    Maybe you should ask admin to make a separate section for this purpose. This section should solely be used for articles that explains how a particular defense system works. I am sure many of us can contribute with something or the other.
     
  2. jagjitnatt

    jagjitnatt Major ELITE MEMBER

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    Actually the forum is based on vBulletin. Its a ready made system and the admin doesn't have control of everything. He can set global settings but can not make individual setting for every section.

    For that he needs to change the code in the config files. He needs to be good with PHP for that. I am not sure he would be willing to do that.
    This forum needs a lot of tweaking and I would be willing to do it but I would need to login as admin for that, which is not possible.

    I can guide him though.
     
  3. Devianz

    Devianz 2nd Lieutant FULL MEMBER

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    Can't we rename an existing section for this?
     
  4. jagjitnatt

    jagjitnatt Major ELITE MEMBER

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    Yes, the admin can do that. But even that section will have limits like 10000 characters and 8 images per post. If admin changes the settings, the settings would be applied to the complete forum and not just that section.

    The admin needs to code the settings into the config file manually.
     
  5. PRATEEK

    PRATEEK FULL MEMBER

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    ANTENNA INTRODUCTION / BASICS​


    RULES OF THUMB:​
    -

    These are very basics of Radar , i will try to explain in simplest manner

    1. The Gain of an antenna with losses is given by:
    [​IMG]


    2. Gain of rectangular X-Band Aperture

    G = 1.4 LW Where: L = length of aperture in cm
    W = width of aperture in cm

    3. Gain of Circular X-Band Aperture
    [​IMG]

    4. Gain of an isotropic antenna radiating in a uniform spherical pattern is one (0 dB).

    5. Antenna with a 20 degree beamwidth has a 20 dB gain.

    6. 3 dB beamwidth is approximately equal to the angle from the peak of the power to the first null (see figure at right).

    7. Parabolic Antenna Beamwidth:
    [​IMG]

    [​IMG]

    --------------------------------------------------------------------------To be cont
     
  6. prototype

    prototype Major SENIOR MEMBER

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    can anyone explain what is the reason radars r unable to catch stealth surfaces,does simply it have anything to do with the materials used,or more with the structure designed,why is it that canards r avoided in a stealth plane
     
  7. PRATEEK

    PRATEEK FULL MEMBER

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    Ok First of all , Let Me clear one thing -
    -there is nothing as uncatchable for a Radar
    -Nothing is invisible to radar even a tiny flying mosquito is visible

    Problem is what distance and distance may be just few KMS in some cases , and a stealth aircraft detects a Non-stealth object before a Stealth fighter is detected itself .

    Now for understanding How an All aspect stealth works we need to understand few terms first
    -RCS (Radar Cross Section) or Radar Returns
    -CLUTTER NOISE / Background Noise
    -IR (infra-red) signature of Object
    -LPI Low probability of intercept working

    Try and read about above 4 terms in wiki , it will be easier for me to explain them meanwhile in subsequent post I am going to explain each of them separately .
     
  8. jagjitnatt

    jagjitnatt Major ELITE MEMBER

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    Radars can detect every physical object in the sky. The thing is some things are detected at far off distances and some are detected too close.

    Stealth aircraft are shaped in such a way that the radio waves striking the surface of the aircraft are deflected in directions different from the direction of the transmitting radio wave.

    Stealth aircraft are also coated with RAM (Radar Absorbent Material). These are paints that have special elements which absorb the radio waves and turn them into heat. This does increase the IR signature of the aircraft but makes it very difficult for radar to detect.

    Canards are avoided because they add another surface to the aircraft which will add another plane in which radio waves will be deflected. More the surface, more will be the radio observability of the aircraft.
     
  9. PRATEEK

    PRATEEK FULL MEMBER

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    RCS ​


    The term rcs is indicative of area that Radar sees from return , means that much area of Jet reflects like a plane mirror back to emitter source .
    [​IMG]
    This is the formula to calculate the area that reflects the radar wave -
    [​IMG]

    Radar waves reflect and scatter in many different ways , Calculations of radar return depend on laws governing the properties of electromagnetic radiation. Electro-magnetic waves behave the same whether their wavelength
    puts them in the radar or optical light regions.
    Maxwell’s equations formulated was able to established boundary conditions for the behavior of electromagnetic waves
    Here is Physics works in ideal condition for return-
    [​IMG]
    Types of return
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    Just use Wiki for these terms of
    Specular Reflection , Diffraction, Scatter and Tail return , Cavities return and Corner Reflection

    [​IMG]

    Basically all above are Returns that are essential for Radar to see the object , how stealth works is by reducing these returns by order of magnitude
     
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  10. PRATEEK

    PRATEEK FULL MEMBER

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    How RCS reduction works

    - Reduce all scattering and diffraction by giving an angled shape + swept wings and try to absorb the radar wave .

    Basically when Radar wave strikes the air-craft surface it does 2 things
    -Firstly it charges up the photons,electrons,protons on surface which increase return by forming a new wave pattern
    -Forms a Travelling wave that runs on surface until it gets a crack to scatter or reflect back
    -Specular reflection occurs

    What we do is shapings+Angulation+Swepping of wings to reduce specular reflection.
    The cracks in the welding etc are smoothened out by using RAM coating and composites.
    Composites act as insulator preventing charging of surface particles , very thick layer prevents Travelling wave and prevent reflection by Grating absorption.
    [​IMG]
    [​IMG]

    There are many additional methods like
    -Canopy treatment - HAVE GLASS2 EFFECT on F16
    -HIDING COMPRESSOR FACE by S-duct or Radar blocker
    -Reducing IR return by mixing with cooled Air vent + Flat Nozzles
    I will discuss all these in future , may be next Sunday

    What all these procedure do is make Returns minimal to hide in clutter noise .
    Since Radar of Stealth aircraft operates in LPI mode + Return from surface and Plume of ionised gases return are so minimal that Aircraft hides itself in Clutter noise and the old Jets Reject these weak signal as clutter noise so are not able to identify threat.


    I will explain Clutter and Noise in next Post
     
  11. prototype

    prototype Major SENIOR MEMBER

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    ^^ thanks for both prateek and jagit for the informative post,i will b waiting for the rest
     
  12. Bad Wolf

    Bad Wolf Major SENIOR MEMBER

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    it mean stealth jet are stealth until they dont move . movement make them visible
     
  13. RoYaN

    RoYaN Lt. Colonel ELITE MEMBER

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    What is the use of a jet let alone a stealth jet if it does not move?????
     
  14. Coltsfan

    Coltsfan <b>SENIOR MEMBER</b> SENIOR MEMBER

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    Where did you find that information?
     
  15. jagjitnatt

    jagjitnatt Major ELITE MEMBER

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    partially true. all things are visible to a radar, but moving things are visible more distinctly. The radars are programmed in such a way
     

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