STEALTH RADARG RAM PRABU

DEVIREDDY PRAMOD REDDYKARRI V R DINESH KUMAR REDDY

IntroductionWhat is Stealth Technology?

• Stealth – movement that is quiet and careful in order not to be seen

or heard (in general), not detectable by radar.

• Radars associated with stealth

1. Radars detecting objects in stealth mode

2. Radars operating in stealth mode

How is stealth achieved?• Reduce RCS of the object by changing its shape.• Smooth edges with flat surfaces, Round wing tips• Radar absorbing materials (RAM)

Commonly used material – Iron Ball Paint

• Heat trails from engines reduced to prevent IR detection• Noise from engines reduced and travels in subsonic speeds to prevent sonic boom.

Stealth Planes and Ships US stealth copter RAH -66

Radars to detect Stealth objects • Bistatic Radar: Multiple transmitters and emitters are used because energy is

scattered in many directions and needs to be captured effectively.• Low Frequency Radar:

• uses frequency lower than 1 GHz • Radar absorbing materials absorb frequency from 2.5 – 13 GHz with an efficiency of 95%

Advantages: • Cost effective,• high range

Disadvantages:• Large size• Doppler unambiguities

Low Frequency Radar - continued• Block diagram:

Radars to detect Stealth objects • Phased Array Radar operating in L-band:

• Consists hundreds or thousands of such blocks each radiating in same phase

Phased Array Radar- continued• Advantages:

Portable Inexpensive to build in mass production

• Disadvantages:Signal processing difficultyPrior knowledge of range and target angle is needed

Radars to detect Stealth objects • Infra Red receivers used to detect chemical and physical signatures of exhaust gas

plume particularly heat from engines.

• Exhaust plume has other characteristics that are detectable, and when coupled with

absence of heat it is certainly a stealth aircraft.

• SONAR (Sound Navigation and Ranging) is used along with these radars for better

results.

• Usually multiple types of radars are used for stealth detection.

• Signals from communication satellites and telephone towers are used by radar

receivers to detect objects (advanced transmitter-less radar).

Some Counter Stealth Radars

Radars operating in stealth mode• Radars that are not detected by other Radars i.e., radars that cannot be jammed are

called as radars operating in stealth mode.

• What is Radar deception and jamming?

Radar jamming and deception (Electronic countermeasure) is the intentional emission of

radio frequency signals to interfere with the operation of a radar by saturating its receiver with

noise or false information.

• Types of Jamming

• Mechanical

• Electronic

Radar Jamming• Mechanical Jamming: by devices which reflect radar energy back to

the radar.• Chaff – metallic strip to reflect different frequency waves.• Corner reflectors – multiple sided reflecting objects.• Decoys – flying objects to deceive a radar by creating clutters.

• Electronic Jamming: Jammers radiate energy signal towards radiating radar.• Spot Jamming – single frequency jammer of high power used.• Sweep Jamming – Multiple frequency & high power at different times.• Barrage Jamming – Multiple frequencies simultaneously, but less effective.• Base Jamming – Main radar jammed in case of multiple radars.• Pulse Jamming – Noise pulses generated to deceive the receiver

DRFM Jamming• Digital radio frequency memory is an electronic method for digitally capturing

and retransmitting RF signal.• Properties changed are :

• Delay in transmitted pulses• Frequency variation

• Creates a false range targets to the radar• Creates Doppler(velocity) errors.

• Blip Enhancement

Counter measures used in stealth radars

• Constantly changing the operating frequency.• Covering the outgoing signal with random noise, makes it more

difficult for a jammer to figure out the frequency that a radar is operating on.• Employing an effective operator who is skilled in signal processing.• Active electronically scanned array (AESA) radars are innately harder

to jam and can operate in Low Probability of Intercept (LPI) .• A quantum radar system would automatically detect attempts at

deceptive jamming.

Active Electronically Scanned Array• Active phased array radar• Transmitter and receiver (transceiver) functions are composed of

numerous small solid-state transmit/receive modules (TRMs). • Spreads the signal emissions out, across a band of frequencies.• Produce numerous simultaneous sub beams that it can recognize due to different frequencies and can track a large no. of targets.• Multiple frequencies generated at once.

Active Electronically Scanned Array• Advantages:• Low probability of intercept.• High jamming resistance.

• Limitation:• The highest Field of View (FOV) for a flat phased array antenna is currently

120°.

References• www.wikipedia.org• www.defensemedianetwork.com• www.foia.cia.gov• www.whale.to• www.dailymail.co.uk• www.researchinventy.com• www.defense-update.com• www.army.mil• www.marines.mil• Books:• Advantages of Bistatic radar• Introduction to radar systems

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