exercise spot noise jamming and burn-through · pdf filethe jamming signal, ... increases the...

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Exercise 1-2

Spot Noise Jamming and Burn-Through Range

EXERCISE OBJECTIVE

Demonstrate the use of spot noise jamming as an electronic countermeasure (ECM)against radar detection. Present the concept of radar burn-through range.

DISCUSSION

Introduction

Spot noise jamming is an electronic countermeasure (ECM), one of the simplestused against search and tracking radars. Its simplicity stems from its fundamentaladvantage: very little knowledge about the enemy radar system is required. Thepurpose of its use is to insert an interference signal into a radar receiver, denying orat the least greatly disturbing target detection and tracking.

A jammer conducting spot noise jamming, directs a narrowband signal toward aradar antenna. The frequency of the noise signal must be tuned to the operatingfrequency of the victim radar. The jamming signal, once received, causes the radarreceiver’s background noise level (against which target returns are detected) toincrease, as seen in Figure 1-11. The added interference to the radar receiver lowersthe signal-to-noise ratio (S/N ratio), degrading radar target detection.

Figure 1-11. The effect of spot noise jamming on the radar receiver detection threshold.


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A low S/N ratio in the radar receiver causes unbalance in the range tracking servosystem resulting in random range gate drift. This also causes unbalance in the angletracking servo system that leads to rapid fluctuations in the angular error signal.These fluctuations, however, do not affect angle tracking because they are filteredout due to the low bandwidth (usually a few Hertz or less) of the antenna servosystem.

Noise Jammer EA Missions

There are four basic EA mission classifications for a platform, the stand-off EA,escort EA, self-screening (self-protection) EA, and the mutual-support (cooperative)EA mission. In air defense situations, spot noise jamming can originate from any oneof these types of platforms. Escort, self-screening, and mutual-support EA platformsdirect their jamming most often through the radar antenna’s mainlobe. In most stand-off EA missions, spot noise jamming is transmitted with enough power to be receivedthrough both the radar antenna’s main and sidelobes. Figure 1-12 shows that in allof these EA missions, except for stand-off, the jammer platforms are found within theinterception range of hostile weapon systems. The self-screening jammer is a loneplatform that uses ECM to protect only itself. It is not involved in a concerted tacticalprotection of friendly forces.

Figure 1-12. Noise jammer ECM missions.


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Jammer Versus Radar Energy Battle

Spot noise jamming used by a self-screening (self-protection) platform truly becomesan energy battle between the radar and the jammer. In order to prevent platformdetection by the radar, the level of noise induced by the jammer signal in the radarreceiver must exceed the amplitude of the platform’s skin return. It must alsoovercome any processing advantages held by the radar. An example of such anadvantage would be the use of coherent video integration, a process whichincreases the S/N ratio of the radar video signal.

However, radar ECCM aside, the true advantage belongs to the jammer. A jammingsignal has only a one-way (to the radar) propagation loss contrasted with the two-way (to the target and back) propagation loss of a radar signal. This implies that thepower of a returned radar signal varies with range as 1/R4, and that the power of ajamming signal varies with range as 1/R2. Figure 1-13 shows the power variationswith range of both the returned radar signal and the jamming signal.

Figure 1-13. Power variation with range for radar target returns and jammer signals.

A subtle point that may not have been obvious is made clear. There exists a certainrange, called the burn-through range, below which the power of the radar returnexceeds the jammer signal power.

Burn-Through Range

As the jammer range from the radar decreases, the amplitude of the radar pulsereturn increases at a faster rate than the jammer noise level in the radar receiver.The situation translates to an increase in the receiver S/N ratio. A target locatedwithin the radar burn-through range produces an echo signal with an amplitude thatexceeds the radar receiver detection threshold (noise level). In this case, the target


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is detected by the radar, and thus, hostile weapon-control systems could lock ontothe target and fire!

The burn-through range can be defined as follows:

1. The minimum range from a radar at which a target is obscured by jamming.

2. The maximum detection range for a radar that is being jammed by a particularplatform.

Radar burn-through range for a specific situation can be calculated using a modifiedversion of the radar range equation. The modified equation includes the effectjamming energy has on the radar receiver. The equation can become quite complex.It is sufficient to know that the burn-through range (RBT) varies as a function of targetradar cross section ( ), average radar transmitter power (Pt), radar antenna gain (G)which itself is dependent on radar frequency (f), and the minimum received targetsignal power required for detection (Smin). Smin is dependent on the jammer powerreceived by the radar (Pj,Rx). These dependencies yield the following relation:

(1)

To minimize the burn-through range, a self-screening platform needs a small radarcross section (RCS) and needs to direct as much jammer power as possible towardthe radar.

A radar, to the contrary, wants to maximize its reflected energy received from atarget in order to maximize the burn-through range. Distinct ECCM, designed tomaximize this range, are available to a radar. Some radars can increase theiraverage transmitter power, dwell longer on target, or increase their antenna gain. Aradar confronted with noise jamming and which increases (with one of the statedtechniques) its radiated energy in the direction of the jammer is operating in burn-through mode.

Procedure Summary

The Tracking Radar, set up in the first part of this exercise, will be used in thesecond part, Spot Noise Jamming, to demonstrate the effects of spot noise jammingon a tracking radar. Spot noise jamming will be produced by the Radar Jamming PodTrainer for self-screening (self-protection).

In the third part of the exercise, Burn-Through Range, you will use the RadarJamming Pod Trainer and Tracking Radar to demonstrate the existence of the radarburn-through range. You will verify the proportionality of the radar burn-throughrange with target RCS.


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PROCEDURE

Setting Up the Tracking Radar

G 1. Before beginning this exercise, the main elements of the Tracking RadarTraining System (i.e., the antenna and its pedestal, the target table, theRTM and its power supply, the training modules, and the host computer)must be set up as shown in Appendix A.

On the Radar Transmitter, make sure that the RF POWER switch is set tothe STANDBY position.

On the Antenna Controller, make sure that the MANual ANTENNAROTATION MODE push button is depressed and the SPEED control is setto the 0 position.

Turn on all modules and make sure the POWER ON LED's are lit.

G 2. Turn on the host computer, start the LVRTS software, select TrackingRadar, and click OK. This begins a new session with all settings set to theirdefault values and with all faults deactivated. If the software is alreadyrunning, click Exit in the File menu and then restart the LVRTS software tobegin a new session.

G 3. Connect the modules as shown on the Tracking Radar tab of the LVRTSsoftware. For details of connections to the Reconfigurable Training Module,refer to the RTM Connections tab of the software.

Note: Make the connections to the Analog/Digital OutputInterface (plug-in module 9632) only if you wish to connect aconventional radar PPI display to the system or obtain anO-scope display on a conventional oscilloscope.

Note: The SYNC. TRIGGER INPUT of the Dual-Channel Samplerand the PULSE GENERATOR TRIGGER INPUT of the RadarTransmitter must be connected directly to OUTPUT B of theRadar Synchronizer without passing through BNC T-connectors.

Connect the hand control to a USB port of the host computer.

G 4. Make the following settings:

On the Radar Transmitter

RF OSCILLATOR FREQUENCY . . . . . . . CAL.PULSE GENERATOR PULSE WIDTH . . . 1 ns

On the Radar Synchronizer / Antenna Controller

PRF . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288 HzPRF MODE . . . . . . . . . . . . . . . . . . . . . SINGLE


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ANTENNA ROTATION MODE . . . . PRF LOCK.DISPLAY MODE . . . . . . . . . . . . . . . POSITION

On the Dual-Channel Sampler

RANGE SPAN . . . . . . . . . . . . . . . . . . . . . 3.6 m

In the LVRTS software

System Settings:Log./Lin. Mode . . . . . . . . . . . . . . . . . . . . Lin.Gain . . . . . . . . . . . . . . . . . . . . . . as required

Radar Display Settings:Range . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 m

G 5. Connect the cable of the target table to the connector located on the rearpanel of the Target Controller. Make sure that the surface of the target tableis free of any objects and then set its POWER switch to the I (on) position.

Place the target table so that its grid is located approximately 1.2 m from theRotating-Antenna Pedestal, as shown in Figure 1-14. Make sure that themetal rail of the target table is correctly aligned with the shaft of theRotating-Antenna Pedestal.

Figure 1-14. Position of the Rotating-Antenna Pedestal and target table.

G 6. Calibrate the Tracking Radar Training System according to the instructionsin Appendix B.


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Set the RF POWER switch on the Radar Transmitter to the STANDBYposition.

G 7. Make sure that the Tracking Radar is adjusted as follows:

Operating Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.0 GHzPulse-Repetition Frequency . . . . . . . . . . . . . . . . . . . . single, 288 HzPulse Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 nsObservation Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 m

Spot Noise Jamming

G 8. Remove the semi-cylinder target, used for the Tracking Radar calibration,from the target table mast.

Turn off the target table. Move the metal rail to either end of the target table.The metal rail will not be used during the exercise.

Place the Radar Jamming Pod Trainer support (part number 9595-10),provided with the Connection Leads and Accessories, onto the target table.Position it so that it is in the center of the target table grid.

Note: Appendix F of this manual illustrates the various itemsincluded in the Connection Leads and Accessories. You can referto this appendix to identify a particular item.

G 9. Make sure that a 50- load is connected to the Radar Jamming Pod TrainerCOMPLEMENTARY RF OUTPUT.

Install the Radar Jamming Pod Trainer onto its support (in the horizontalposition) using the short support shaft (part number 33125).

Align the Radar Jamming Pod Trainer so that its horn antennas are facingthe Tracking Radar antenna and aligned with the shaft of the Rotating-Antenna Pedestal. The longitudinal axis of the Radar Jamming Pod Trainershould be aligned with the shaft of the Rotating-Antenna Pedestal.

Rotate the infrared receiver on the Radar Jamming Pod Trainer toward thedirection from which you will use the remote controller.

Install the Power Supply (Model 9609) of the Radar Jamming Pod Traineron the shelf located under the surface of the target table. Connect thePower Supply line cord to a wall outlet.

Connect the power cable of the Radar Jamming Pod Trainer to the multi-pinconnector located on top of the Power Supply.

Retract the Radar Jamming Pod Trainer's target positioning arm and placethe medium-size (15 x 15 cm) metal plate target at its tip (refer toFigure 1-15). Orient the metal plate target so that it squarely faces theTracking Radar antenna. The target should be perpendicular to thelongitudinal axis of the Radar Jamming Pod Trainer.


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Figure 1-15. Installing a target on the target positioning arm of the Radar Jamming Pod Trainer.

G 10. On the Radar Transmitter, depress the RF POWER push button. The RFPOWER ON LED should start to flash on and off. This indicates that RFpower is being radiated by the Dual Feed Parabolic Antenna.

In LVRTS, turn off the AGC of the Radar Target Tracker.

Turn on the Power Supply of the Radar Jamming Pod Trainer. Turn theRadar Jamming Pod Trainer on.

Note that the Radar Jamming Pod Trainer status indicates that the Repeateris on. This means that the Radar Jamming Pod Trainer is receiving the radiopulses transmitted by the Tracking Radar, amplifying them, and sendingthem back to the radar.

G 11. Turn the repeater of the Radar Jamming Pod Trainer off by making thefollowing settings on the remote controller:

Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffAM/Blinking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffRepeater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffRGPO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffFalse Targets (FT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Off

After having made the above adjustments, point the remote controllertoward the Radar Jamming Pod Trainer. While observing the infraredreceiver, press the remote controller SEND button.

Verify that the Radar Jamming Pod Trainer status, indicated on its rearpanel, shows that no jamming signal is being transmitted.


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G 12. Make sure the radar antenna axis is aligned with the Radar Jamming PodTrainer. This can be done by observing the O-Scope Display of the TrackingRadar while adjusting the radar antenna orientation so that the amplitude ofthe Radar Jamming Pod Trainer's natural echo signal (radar echo signal ofthe metal plate installed on the target positioning arm) is the same for bothpositions of the antenna main beam.

Observing the O-Scope Display, set the Gain of the MTI Processor so thatthe amplitude of the Radar Jamming Pod Trainer's natural echo signal isapproximately 0.25 V.

Lock the Tracking Radar onto the Radar Jamming Pod Trainer's naturalecho signal.

G 13. Verify that the Tracking Radar has a steady tracking lock on the RadarJamming Pod Trainer by carefully sliding it backward by about 15 cm,sliding it sideways by about 10 to 15 cm, and then bringing it back to itsinitial position.

G 14. In LVRTS, disconnect Oscilloscope probes 1 and 2 from TP1 and TP2 of theMTI Processor. Leave probe E connected to TP8 of the Radar TargetTracker. Connect Oscilloscope probes 1 and 2 to TP15 and TP26 of theRadar Target Tracker, respectively.

Make the following settings on the Oscilloscope:

Channel 1 . . . . . . . . . . . . . 20 mV/div (AC coupled)Channel 2 . . . . . . . . . . . . . . 0.1 V/div (DC coupled)Time Base . . . . . . . . . . . . . . . . . . . . . . . . . 5 ms/div

Set the Oscilloscope to Continuous Refresh.

G 15. Observe the signals at TP15 and TP26 on the Oscilloscope. TP15 is therange gate distance control signal, and TP26 is the angular error signal forthe Tracking Radar. Note that the signals at TP15 and TP26 show smallamplitude fluctuations with time.

Explain the reason for the signal amplitude fluctuations?


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G 16. Using the remote controller, make the following adjustments to the RadarJamming Pod Trainer:

Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OnFrequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.0 GHzFrequency Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . 0.0 GHzFrequency Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . TriangleAttenuation 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~15 dBAttenuation 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 dB

AM/Blinking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffRepeater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffRGPO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffFalse Targets (FT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Off

This enables the Voltage Controlled Oscillator (VCO) of the Radar JammingPod Trainer and sets its operating frequency to 8.0 GHz, the samefrequency as the Tracking Radar. The Radar Jamming Pod Trainer is thustransmitting a spot noise jamming signal toward the radar antenna.

Observe the range gate distance control signal (TP15) and the angular errorsignal (TP26) on the Oscilloscope. Briefly explain why the signal amplitudefluctuations have increased.

Note: Change the sensitivity settings on the Oscilloscope asrequired.

G 17. In LVRTS, add persistence to the O-Scope Display by setting thecorresponding parameter to 6 traces.

Using the remote controller, slowly decrease the Radar Jamming PodTrainer Noise Attenuation 1 dB at a time while observing the noise level onthe O-Scope Display, and the signals at TP15 and TP26 on theOscilloscope.

Does the noise level on the O-Scope Display gradually increase, therebydecreasing the S/N ratio?

G Yes G No

Briefly explain what occurs to range tracking as the Radar Jamming PodTrainer noise level increases.


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Briefly explain what occurs to angle tracking as the Radar Jamming PodTrainer noise level increases.

G 18. Using the remote controller, set the Radar Jamming Pod Trainer NoiseAttenuation to maximum and turn the Noise off.

In LVRTS, disable the persistence of the O-Scope Display by setting thecorresponding parameter to Off.

Burn-Through Range

Note: The following manipulations must be performed with greatcare to ensure a successful demonstration of the burn-throughrange.

G 19. Move the target table carefully so that its grid is located approximately 1.8 mfrom the Rotating-Antenna Pedestal, as shown in Figure 1-16. Make surethat the longitudinal axis of Radar Jamming Pod Trainer remains alignedwith the shaft of the Rotating-Antenna Pedestal.

Figure 1-16. Position of the target table with respect to the Rotating-Antenna Pedestal.


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Slide the Radar Jamming Pod Trainer along the target table Y-axis so thatit is at the end of the target table farthest from the Tracking Radar antenna(coordinates X = 45 cm and Y = 87 cm).

If necessary, realign the longitudinal axis of the Radar Jamming Pod Trainerwith the shaft of the Rotating-Antenna Pedestal. Make sure that the metalplate target is perpendicular to the longitudinal axis of the Radar JammingPod Trainer.

G 20. In LVRTS, set the Lobe Control Rate of the Radar Target Tracker toOFF (right). This disables antenna lobe switching, leaving only the right lobeof the Tracking Radar antenna in operation.

Slightly rotate the Tracking Radar antenna counterclockwise until theamplitude of the Radar Jamming Pod Trainer's natural echo signal ismaximum on the O-Scope Display. The Radar Jamming Pod Trainer'snatural echo signal should be near the right-hand side end of the O-ScopeDisplay.

Slide the Radar Jamming Pod Trainer forward and backward by afew millimeters (to slightly vary its range) so as to maximize the amplitudeof its natural echo signal on the O-Scope Display.

Note: Be careful not to change the alignment of the RadarJamming Pod Trainer when you slide it forward and backward.

The amplitude of the Radar Jamming Pod Trainer's natural echosignal varies slightly with range due to minor imperfections in theRadar Training System.

In LVRTS, set the Gain of the MTI Processor so that the amplitude of theRadar Jamming Pod Trainer's natural echo signal on the O-Scope Displayis approximately 0.25 V.

In LVRTS, add persistence to the O-Scope Display by setting thecorresponding parameter to 12 traces.

G 21. Using the remote controller, turn the Radar Jamming Pod Trainer Noise onwhile observing the O-Scope Display. Decrease the Noise Attenuation untilthe Radar Jamming Pod Trainer's natural echo signal is on the threshold ofbeing completely lost in noise. That is, you are almost no longer able todistinguish, on the O-Scope Display, the echo signal from the jamming noise(see Figure 1-17).

At this distance, is the Radar Jamming Pod Trainer within the radar burn-through range?

G Yes G No


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Figure 1-17. The Radar Jamming Pod Trainer's natural echo signal as seen on an O-Scope

Display.

G 22. While observing the O-Scope Display, slowly slide the Radar Jamming PodTrainer toward the Tracking Radar antenna and along the Y-axis of thetarget table until it reaches the other end of the target table (coordinatesX = 45 cm and Y = 3 cm).

Note: When sliding the Radar Jamming Pod Trainer, be carefulto keep its longitudinal axis aligned with the shaft of the Rotating-Antenna Pedestal as perfectly as possible.

On the Radar Jamming Pod Trainer, temporarily turn the Noise off using theremote controller.



On the Radar Jamming Pod Trainer, turn the Noise on using the remotecontroller. The Radar Jamming Pod Trainer is located at the burn-throughrange. It can be detected and tracked by the Tracking Radar. Figure 1-18shows an example of what you might observe on the O-Scope Display.


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Figure 1-18. Radar Jamming Pod Trainer's natural echo signal no longer protected by spot noise

jamming.

Briefly explain why the Radar Jamming Pod Trainer's natural echo signalcan be detected by the Tracking Radar at this closer range, when at theprevious longer range it was hidden by spot noise jamming.

G 23. Slide the Radar Jamming Pod Trainer mast along the target table Y axis sothat it is at the end of the target table farthest from the Tracking Radarantenna (coordinates X = 45 cm and Y = 87 cm). The Radar Jamming PodTrainer's natural echo signal should be on the threshold of being completelylost in noise once again.

G 24. On the Radar Jamming Pod Trainer, temporarily turn the Noise off using theremote controller.


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In LVRTS, disable the persistence of the O-Scope Display by setting thecorresponding parameter to Off.

G 25. If necessary, realign the longitudinal axis of the Radar Jamming Pod Trainerwith the shaft of the Rotating-Antenna Pedestal. Make sure that the metalplate target is perpendicular to the longitudinal axis of the Radar JammingPod Trainer.

Readjust the radar antenna orientation slightly so that the amplitude of theRadar Jamming Pod Trainer's natural echo signal is maximum on theO-Scope Display.



In LVRTS, set the Gain of the MTI Processor so that the amplitude of theRadar Jamming Pod Trainer's natural echo signal on the O-Scope Displayis approximately 0.25 V.

G 26. In LVRTS, add persistence to the O-Scope Display by setting thecorresponding parameter to 12 traces.

On the Radar Jamming Pod Trainer, turn the Noise on using the remotecontroller. While observing the O-Scope Display, adjust the NoiseAttenuation so that the Radar Jamming Pod Trainer's natural echo signal ison the threshold of being completely lost in noise, as you did previously inthis exercise (see Figure 1-17). This prevents reliable target detection. TheRadar Jamming Pod Trainer is therefore beyond the burn-through range.

G 27. Using the remote controller, turn the Radar Jamming Pod Trainer Noise off.

Replace the medium-size metal plate target installed on the targetpositioning arm of the Radar Jamming Pod Trainer by the large (20 x 20 cm)metal plate target. Orient the large metal plate target so that the amplitudeof its echo signal on the O-Scope Display is maximum. Radar Jamming PodTrainerReplacing the medium-size metal plate target by the large metalplate target is a means to increase the radar cross section (RCS) of theRadar Jamming Pod Trainer.

G 28. Using the remote controller, turn the Radar Jamming Pod Trainer Noise on.Can the Radar Jamming Pod Trainer's natural echo signal be distinguishedfrom noise on the O-Scope Display?

G Yes G No


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Is the Radar Jamming Pod Trainer still beyond the burn-through range?

G Yes G No

From your observations, how is the burn-through range related to the target(self-screening jammer) RCS?

G 29. Turn off the Tracking Radar and the Radar Jamming Pod Trainer.Disconnect all cables and remove all accessories.

CONCLUSION

Spot noise jamming is a simple electronic attack against search and tracking radars.You observed that it is produced by inserting a narrowband RF interference signalinto a radar receiver, via the radar antenna. The signal must be tuned to the victimradar’s operating frequency. You observed that it is meant to greatly disturb radartarget detection and tracking by masking the jammer echo signal. It was seen in theexercise discussion that spot noise jamming is often implemented by self-screeningjammers: Lone platforms that use electronic warfare countermeasures for self-protection.

It was stated that the power of a radar target return varies as 1/R4, whereas that ofa jamming signal varies as 1/R2. You observed that as the range R of the RadarJamming Pod Trainer decreased, a distance was reached where the echo signalpower exceeded the received jamming power, allowing target detection. Thisdistance is known as the radar burn-through range, it was defined to be the rangefrom a radar at which a target is no longer obscured by noise jamming. Youobserved that the radar burn-through range is proportional to the RCS of a self-screening jammer, and is inversely proportional to the jamming power received bythe radar.

REVIEW QUESTIONS

1. Briefly explain how spot noise jamming affects the performance of a trackingradar.


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2. What are the jamming power and RCS characteristics that a self-screeningjammer must have to minimize the radar burn-through range?

3. Complete the following sentence: A radar wants the energy received from atarget to be maximized so that ... ?

4. The radar burn-through range varies as a function of what variables? Statewhether the radar burn-through range is directly or inversely proportional to eachof the variables.

5. Spot noise jamming has been shown to work effectively against the Lab-VoltTracking Radar which uses antenna lobe switching. Would it also workeffectively against a monopulse or a conical scan radar? Why?

exercise spot noise jamming and burn-through · pdf filethe jamming signal, ... increases the...

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