Radar in an Active Target Environment, 2-1 Deception Jamming Using the Radar Jamming ...€¦ ·...

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Exercise 2-1

Deception Jamming Using the Radar Jamming Pod Trainer

EXERCISE OBJECTIVE

To familiarize yourself with the operation of the repeater circuit and the on-offmodulation switch of the Radar Jamming Pod Trainer.

DISCUSSION

The Radar Jamming Pod Trainer can produce various types of DECM signals, all ofwhich are covered in the present manual (see Table 2-2). Different jammer operatingparameters are associated with each jamming technique. These parameters havea direct impact upon the jammer’s effectiveness against a radar. The value of thejammer operating parameters are thus dependent upon the type of jamminggenerated and the characteristics of the victim radar. The operating parameters mustbe adjusted so that the jamming against the targeted radar be as effective aspossible.

For example, the carrier frequency of a spot noise jamming signal is one of thejammer’s operating parameters. If the jammer operating parameter is not adjustedproperly, for instance, to a frequency that is not within the radar receiver’s passband,then the jammer EA is ineffective against the radar. The remote controller and theexternal control inputs found on the back panel of the Radar Jamming Pod Trainer,are used to set the jammer's operating parameters. Using the remote controller,various jamming techniques can be enabled and their related operating parameterscan be set, or otherwise input into the Radar Jamming Pod Trainer via the externalcontrol inputs.


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DECM DESCRIPTION

An

gle

Decep

tio

nAsynchronous InverseGain Jamming

Transmit a repeated radar signal withasynchronous on-off modulation.

AM Noise Transmit a noise jamming signal with on-offmodulation.

Cross-PolarizationJamming

Transmit noise or a repeated radar signalwith polarization opposite to that of the radar.

Cooperative Jamming Coordinate transmission between two ormore spatially dispersed jammers.

Ran

ge D

ecep

tio

n False Target RepeaterJamming

Transmit a repeated radar echo signal witha specific delay.

Range Gate Pull-Off(RGPO) Jamming

Capture the tracking radar range gate witha strong repeated echo signal and steal itaway from the true tracked target.

Table 2-2. Radar Jamming Pod Trainer DECM.

Programmable Delay Line

A programmable delay line is the cornerstone of the Radar Jamming Pod Trainerrepeater circuit. All Radar Jamming Pod Trainer range gate DECM are generatedusing the programmable delay line. Only one path length can be operational at atime as indicated in Figure 2-1. Eight different path lengths are available in theprogrammable delay line. To generate the Radar Jamming Pod repeated echo signalin the first exercise of Unit 1, the shortest path of the programmable delay line wasselected.


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Figure 2-1. The Radar Jamming Pod Trainer repeater circuit.

Using the remote controller false target (FT) menu, the path length of the repeatercircuit can be configured to take either one of two longer pre-programmed delay linepaths. These delay line paths are longer than that used when the Repeater wasturned on in the first exercise of Unit 1. When the repeater circuit delay islengthened, the Radar Jamming Pod Trainer is said to be in False Target (FT)jamming mode. Having a different path length, the false targets appear to a radaroperator as having a different range.

False target jamming can have serious effects on a search radar’s ability to detecttrue targets. As shown in Figure 2-2, a jammer that simulates increased numbers ofplatforms can avoid the watchful eye of search radar operators and slip into theweapons range of enemy tracking radars.


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Figure 2-2. False target jamming effect on a search radar PPI display.

Range gate pull-off (RGPO) uses the programmable delay line of the repeater circuit.The Radar Jamming Pod Trainer can be made to consecutively and repetitivelyswitch through the different delay line path lengths when set in repeater mode.Depending on the RGPO walk-off time, the repeated echo signal can be imposeddifferent range rates (speeds).

On-Off Modulation

Asynchronous inverse gain jamming, AM noise, and certain cooperative jammingtechniques are generated by the Radar Jamming Pod Trainer using on-offmodulation. On-off modulation is applied to the transmitted RF signal by repetitivelythrowing an SPDT RF switch between its two poles. This is done using an externallyor internally generated square-wave signal to control the SPDT RF switch. In thismanner, the generated jamming signal is found to be alternately and repetitivelydirected toward the Radar Jamming Pod Trainer transmission horn antenna, andthen toward the COMPLEMENTARY RF OUTPUT on the rear panel. The effect ison-off modulation of the transmitted jamming signal, be it transmitted through theRadar Jamming Pod Trainer horn antenna or, through an auxiliary antennaconnected to the COMPLEMENTARY RF OUTPUT. Note that when transmittingthrough the Radar Jamming Pod Trainer horn antenna only, a 50- load must beconnected to the COMPLEMENTARY RF OUTPUT.

As stated, on-off modulation can be controlled with an internal signal having presetswitching frequency values. Internal or external control is enabled through theremote controller AM/Blinking menu. When controlled externally, the switchingfrequency for the SPDT RF switch corresponds to the frequency of a square-waveTTL signal applied to the EXTERNAL AM/BLINKING CONTROL INPUT found on theRadar Jamming Pod Trainer’s rear panel.


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Procedure Summary

During the first part of this exercise, you will set up and calibrate the Tracking Radar.You will also position the Target Positioning System with respect to the TrackingRadar.

In the next two parts of the exercise, the Radar Jamming Pod Trainer programmabledelay line is used to generate two different types of range deception jammingtechniques. The characteristics and performances of the programmable delay lineare observed.

During exercise part four, you will use the SPDT RF switch to on-off modulate theRadar Jamming Pod Trainer’s transmitted signal. You will verify that on-offmodulation can be applied to a noise signal, as well as, to the repeater signal.

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.


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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 . . . . . . . . . . . . . . . . . . . . . SINGLEANTENNA 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 2-3. Make sure that themetal rail of the target table is correctly aligned with the shaft of theRotating-Antenna Pedestal.


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Figure 2-3. Position of the Rotating-Antenna Pedestal and target table.

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

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

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

False Target Jamming

G 7. 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.


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G 8. 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 long support shaft (part number 33125-01).

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.

G 9. 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 Trainerstatus indicates that the Repeater is on. Adjust the remote controller settingsto match the Radar Jamming Pod Trainer status (the Repeater is on, all elseis off).

G 10. 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 repeated echo signal is the same for bothpositions of the antenna main beam.

G 11. Observing the O-Scope Display, set the Gain of the MTI Processor so thatthe amplitude of the Radar Jamming Pod Trainer's repeated echo signal isapproximately 0.25 V.

Measure and record in Table 2-3 the radar range and amplitude of therepeated echo signal, as read off the O-Scope Display.


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RADAR RANGE

(m)

SIGNAL AMPLITUDE

(V)

Repeated Echo

Signal

FT1 Signal

FT2 Signal

Table 2-3. Repeated echo signal range and amplitude measurements.

G 12. Using the remote controller, make the following adjustments to the RadarJamming Pod Trainer:

Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffAM/Blinking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffRepeater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OnRGPO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffFalse Target 1 (FT1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OnFalse Target 2 (FT2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Off

The Radar Jamming Pod Trainer is now transmitting the FT1 false targetjamming signal. Note that to enable false target jamming the Repeater mustbe turned on. In effect, the Repeater delay has been increased by using alonger path of the programmable delay line.

G 13. Measure and record in Table 2-3 the radar range and amplitude of the FT1repeated echo signal, as read off the O-Scope Display.


Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffAM/Blinking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffRepeater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OnRGPO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffFalse Target 1 (FT1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffFalse Target 2 (FT2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . On

The Radar Jamming Pod Trainer is now transmitting the FT2 false targetjamming signal.

G 15. Measure and record the radar range and amplitude of the FT2 repeatedecho signal in Table 2-3, as read-off the O-Scope Display.


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G 16. Using the values that you recorded in Table 2-3, verify whether theamplitude of the Radar Jamming Pod Trainer's repeated echo signaldecreases as 1/R4, where R is radar range.

Does the repeated echo signal have the described amplitude relation withradar range?

G Yes G No

Briefly explain if it is important for a jammer that produces false targetjamming to have a signal propagation loss comparable to that which occurswith a true target.

G 17. Select the SCAN mode of the Tracking Radar to place it into surveillance(search) mode. This causes the Tracking Radar antenna to rotate.

Notice that each target displayed on the Radar Display appears as twoadjacent blips and is segmented. This is normal and due to the antenna lobeswitching performed by the Tracking Radar.

In LVRTS, set the Lobe Control Rate of the Tracking Radar to Off (Right).to disable antenna lobe switching. Notice that the targets are displayednormally on the Radar Display.

While observing the Radar Display, adjust the Gain of the MTI Processor ofthe Tracking Radar (if necessary) so that the Radar Jamming Pod Trainer'sFT2 repeated echo signal is clearly visible, but not immersed in clutter.

Observing the Radar Display, is there a visible difference between a trueradar target echo and the present false target jamming signal transmitted bythe Radar Jamming Pod Trainer?

G Yes G No

Range Gate Pull-Off (RGPO)

G 18. Select the MANUAL mode of the Tracking Radar to stop the antennarotation.

Note: The Lobe Control Rate of the Radar Target Tracker isautomatically set to PRF/2 when the MANUAL mode is selected.


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Align the axis of the radar antenna with the Radar Jamming Pod Trainer.

While observing the O-Scope Display of the Tracking Radar, slightlyreadjust the radar antenna orientation so that the amplitude of the 's FT2repeated echo signal is the same for both positions of the antenna mainbeam.


Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffAM/Blinking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffRepeater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OnRGPO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . On

Walk-Off Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.0 sFalse Targets (FT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Off

The Radar Jamming Pod Trainer is now transmitting RGPO jamming towardthe Tracking Radar.

G 20. Observing the O-Scope Display, briefly describe RGPO jamming.

G 21. What is the average range difference, Raverage, between the RadarJamming Pod Trainer’s delayed repeated echo signals produced withRGPO jamming?

Raverage = m

Compare the length of Raverage to the radar’s present pulse length(LP = c 0.30 m). Is Raverage greater, equal, or smaller than the radar’spulse length?

Do you think that the radar could track the RGPO repeated echo signal ifRaverage was longer than the radar’s pulse length? Briefly explain your

answer.


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G 22. Using the remote controller to switch between false target jamming andRGPO jamming, answer the following question. FT1 and FT2 correspondto which delay line path lengths?

On-Off Modulation


Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffAM/Blinking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . On

Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 HzControl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internal (INT)

Repeater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OnRGPO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffFalse Target 1 (FT1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffFalse Target 2 (FT2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . On

The Radar Jamming Pod Trainer is now transmitting the FT2 false targetjamming signal with a 0.5-Hz on-off modulation.

Briefly describe the effect of the on-off modulation applied to false targetjamming, as observed on the O-Scope Display.


Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OnFrequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.0 GHzFrequency Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . 0.0 GHzFrequency Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . TriangleAttenuation 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 dBAttenuation 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 dB

AM/Blinking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OnFrequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 HzControl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internal (INT)

Repeater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffRGPO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OffFalse Targets (FT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Off

The Radar Jamming Pod Trainer is now transmitting an on-off modulatedspot noise jamming signal.


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Observe the radar video signal on the O-Scope Display. Does the jammingnoise disappear and reappear at a frequency matching the on-off jammingmodulation frequency?

G Yes G No

G 25. Turn off the Tracking Radar and the Radar Jamming Pod Trainer.Disconnect all cables and remove all accessories.

CONCLUSION

In this exercise, you became familiar with the repeater circuit and the on-offmodulation capability of the Radar Jamming Pod Trainer, both of which are used togenerate DECM. The programmable delay line, an integral part of the repeatercircuit, is intended to generate range deception jamming, and the on-off modulationswitch is intended to generate angular deception jamming.

Using the remote controller, you performed basic operations related to theprogrammable delay line of the repeater circuit. The false target jamming mode wasenabled by increasing the repeater circuit delay (i.e., by using either one of twolonger delay line path lengths). You measured the false target jamming signalamplitudes and concluded that they did not have a 1/R4 propagation loss withrange (R).

You enabled RGPO jamming with a lengthy walk-off time (8 s). You confirmed thatthe Radar Jamming Pod Trainer uses a programmable delay line designed with eightdifferent path lengths. Using the O-Scope Display, you confirmed that consecutiveRGPO jamming repeated echo signals had a range difference that is less than theradar's pulse length (LP). You compared the positions on the O-Scope Display of thefalse target signals (FT1 and FT2) with those of the RGPO repeated echo signals.This allowed you to determine the pre-programmed delay line path lengths that wereused to generate false target signals FT1 and FT2.

Using the remote controller, you internally controlled the on-off modulationfrequency. You demonstrated that it was possible to on-off modulate the repeatedecho signal as well as the noise jamming signal produced by the Radar JammingPod Trainer.

REVIEW QUESTIONS

1. What is the difference between the repeated echo signal, false target jammingsignals, and RGPO jamming signal of the Radar Jamming Pod Trainer?


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2. Briefly explain how the Radar Jamming Pod Trainer creates on-off modulation.

3. Why is the programmable delay line only useful for range deception jammingtechniques?

4. Consider that a sequential lobing radar is tracking a platform. The platformbegins to conduct repeater jamming. What would occur if the delay applied bythe jammer was slightly less than the radar’s interpulse period? What would bethe use of this jamming technique?

5. Consider the Radar Jamming Pod Trainer. It is conducting spot noise jammingwith slow on-off modulation against the Tracking Radar. What is the effect of theon-off modulation on the noise that is induced in the radar receiver system?

Radar in an Active Target Environment, 2-1 Deception Jamming Using the Radar Jamming ...€¦ ·...

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