Exercise 3-2. Cross-Polarization Jamming EXERCISE OBJECTIVE

Exercise 3-2 Cross-Polarization Jamming EXERCISE OBJECTIVE To introduce the concept of antenna polarization. To demonstrate the effect of crosspolarization jamming on a tracking radar s angular error signal. DISCUSSION All electromagnetic signals, be they in the radio, visible, or infrared frequencies of the spectrum, can be regarded as propagating waves consisting of an oscillating electric and magnetic field. The fields oscillate orthogonal to each other, and to their direction of propagation. All antennas can be characterized by their polarization. That is, the direction in which the electric field of the transmitted signal is vibrating, and the direction in which the electric field of a signal must be vibrating to be properly received by the antenna. An antenna s polarization can either be linear, circular, or elliptical, as shown in Figure 3-10. The name given to the polarization describes the path traced out by the electric field vector in a plane perpendicular to the direction of propagation of the signal. Antenna polarization agility can be used as a method of signal discrimination to protect the radar from the effects of jamming. A cross-polarized signal, a signal whose polarization is orthogonal to that of the antenna s, is greatly attenuated upon reception. Therefore a radar, by controlling the polarization of its antenna, can suppress the effects of the jamming signal. In theory, an infinite amount of suppression can be achieved if the radar is vertically polarized, and the jammer horizontally polarized. Practically, however, antenna design limitations restrict the actual level of suppression to a finite value. 3-25

Figure 3-10. Types of signal polarization. That is to say, distortions in an antenna s polarization make it able to receive crosspolarized signals of very strong levels. The polarization distortion is especially prominent in reflector-type antennas due to the curvature of the reflector. Because the antenna polarization distortion is a design weakness, the antenna s crosspolarized response (called Condon lobes) is considerably different than its normally polarized (co-polarized) response, as is illustrated in Figure 3-11 (a). An antenna s 3-26

polarization distortion is caused by several other phenomenon, such as the curvature of the radome (if any), and diffraction of the received signal at the edges of the antenna. As shown in Figure 3-11 (a), the specific level of polarization isolation that an antenna exhibits between a co-polarized signal, and a cross-polarized signal is proportional to the difference between the co-polarized and cross-polarized gains for the signal. Cross-Polarization Jamming The primary use of cross-polarization jamming is as self-protection against a tracking radar, it is not used as a support jammer technique. As stated in this Unit's Discussion of Fundamentals, cross-polarization jamming is a type of defect jamming. It is generally used against monopulse radars that have antennas exhibiting a significant cross-polarized response. As shown in Figure 3-11 (b), cross-polarization jamming exploits the fact that the antenna s response to cross-polarized signals (Condon lobes) drastically changes the relationship between the actual angletracking error, and the angular error signal produced by the radar s tracking servomechanism. Close examination of the co-polarized and cross-polarized difference patterns in Figure 3-11 (b) reveals that they are the inverse of each other (especially around the antenna beam axis). This can be used against monopulse tracking radars to invert the polarity of the angular error signal produced by the tracking mechanism. By transmitting a cross-polarized repeated signal toward a radar antenna, a jammer can create a significant angular tracking offset, on the order of 5 between the antenna boresight and the target s angular position. Once the repeated signal has captured the radar s tracking gates, the polarity of the radar s angular error signal is inverted for small angular tracking errors. The radar responds by rotating the antenna in the wrong direction until the angular error signal takes on a value of zero again, thus causing an angular tracking offset. 3-27

Figure 3-11. Co-polarized and cross-polarized antenna responses and monopulse difference patterns. 3-28

For cross-polarization jamming to be effective, the jammer must provide a high jamming-to-signal (J/S) power ratio, it must be high enough to overcome the victim radar antenna s low-response to cross-polarized signals. The orthogonality of the jamming signal to the radar s must also be as perfect as possible. The slightest deviation from true cross-polarization will allow a component of the jamming signal to be received by the radar antenna via its normal polarization. In general, a bit less than 5 from true cross-polarization is all that is required for the jammer signal to become a beacon for target tracking. However, to satisfy these stringent orthogonality requirements a cross-polarization jammer usually uses a configuration of antennas that enable it to produce cross-polarized jamming independent of the angle of the radar and the jammer, as shown in Figure 3-12. Figure 3-12. Cross-polarization jammer antenna configuration. Most jammers employ either circularly polarized, or linearly (slant) polarized jamming antennas that inevitably have large cross-polarized components. Radars equipped with an antenna that is susceptible to cross-polarized jamming signals can defeat the signal s effects by replacing the antenna with a phased-array (flat panel) antenna, that in general has a small cross-polarized response, or by using a polarization screen that prevents entry of cross-polarized signals. Many military radars have the ability to change the polarization of their transmitted signal, and are thus able to defeat a cross-polarized jammer by using polarization agility. Cross-Polarization Jamming Against a Sequential-Lobing Tracking Radar Figure 3-13 illustrates the effect which cross-polarization jamming has on a sequential-lobing tracking radar. 3-29

Figure 3-13. Effect of cross-polarization jamming on a sequential-lobing tracking radar. 3-30

The upper part of Figure 3-13 shows the normal-polarization response of the radar antenna for the two positions of the main beam. It also shows the cross-polarization response of the radar antenna. As can be seen, the cross-polarization response differs greatly from the normal-polarization response. The main beam in the normalpolarization antenna response is split into two lobes in the cross-polarization antenna response. Furthermore, the amplitude of these lobes (Condon lobes) in the crosspolarization antenna response is much lower ( 24 db in Figure 3-13) than that of the main beam in the normal-polarization antenna response. These differences between the normal-polarization and cross-polarization responses of the radar antenna drastically change the relationship between the actual angular error and the angular error voltage that is produced by the tracking servomechanism, as shown in the lower part of Figure 3-13. The angular error voltage obtained with a cross-polarized signal is lower than that obtained with a co-polarized signal. Furthermore, the polarity of the angular error voltage is inverted for low angular errors (up to ±5 in Figure 3-13). This is the key difference that allows crosspolarization jamming to produce angular deception in a tracking radar. When a low angular error occurs, the angular tracking servomechanism rotates the antenna in the wrong direction until the angular error voltage is zero again. This creates a significant angular offset (+5 or 5 in Figure 3-13) between the antenna axis direction and the target angular position. Procedure Summary During the first part of the exercise, you will set up and calibrate the Tracking Radar. You will also position the Target Positioning System with respect to the Tracking Radar. In exercise part two, the Radar Jamming Pod Trainer is set up. A noise jamming signal will be directed toward the Tracking Radar with the Radar Jamming Pod Trainer in horizontal (0 ), slanted (45 ), and vertical (90 ) positions. This will allow you to determine the type of polarization used by the Tracking Radar and Radar Jamming Pod Trainer antennas, as well as to demonstrate radar polarization agility as a method to defeat noise jamming. During the third part of the exercise, you will use a co-polarized noise jamming signal to measure and record the amplitude of the Tracking Radar s angular error signal as a function of the actual position of the Radar Jamming Pod Trainer with respect to the radar antenna axis. You will perform the same measurement with a crosspolarized noise jamming signal. You will then use the recorded data to plot curves of the angular error signal amplitude versus the Radar Jamming Pod Trainer position, that illustrate the radar's response to co-polarized and cross-polarized jamming signals. This will allow you to make conclusions as to the reasons why cross-polarized jamming is efficient against tracking radars. In the final part of the exercise, you will demonstrate the effect which crosspolarization jamming has on angular target tracking. 3-31

PROCEDURE Setting Up the Tracking Radar G 1. Before beginning this exercise, the main elements of the Tracking Radar Training System (i.e., the antenna and its pedestal, the target table, the RTM 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 to the STANDBY position. On the Antenna Controller, make sure that the MANual ANTENNA ROTATION MODE push button is depressed and the SPEED control is set to 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 Tracking Radar, and click OK. This begins a new session with all settings set to their default values and with all faults deactivated. If the software is already running, click Exit in the File menu and then restart the LVRTS software to begin a new session. G 3. Connect the modules as shown on the Tracking Radar tab of the LVRTS software. 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 Output Interface (plug-in module 9632) only if you wish to connect a conventional radar PPI display to the system or obtain an O-scope display on a conventional oscilloscope. Note: The SYNC. TRIGGER INPUT of the Dual-Channel Sampler and the PULSE GENERATOR TRIGGER INPUT of the Radar Transmitter must be connected directly to OUTPUT B of the Radar 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 3-32

On the Radar Synchronizer / Antenna Controller PRF............................ 288 Hz PRF MODE..................... SINGLE 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 rear panel of the Target Controller. Make sure that the surface of the target table is 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 the Rotating-Antenna Pedestal, as shown in Figure 3-14. Make sure that the metal rail of the target table is correctly aligned with the shaft of the Rotating-Antenna Pedestal. Figure 3-14. Position of the Rotating-Antenna Pedestal and target table. 3-33

G 6. Calibrate the Tracking Radar Training System according to the instructions in Appendix B. Set the RF POWER switch on the Radar Transmitter to the STANDBY position. Make sure that the Tracking Radar is adjusted as follows: Operating Frequency.............................. 9.0 GHz Pulse-Repetition Frequency.................... single, 288 Hz Pulse Width........................................ 1 ns Observation Range................................. 3.6 m Signal Polarization 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. G 8. Make sure that a 50- load is connected to the Radar Jamming Pod Trainer COMPLEMENTARY RF OUTPUT. Install the Radar Jamming Pod Trainer onto its support (in the horizontal position) using the long support shaft (part number 33125-01). Align the Radar Jamming Pod Trainer so that its horn antennas are facing the Tracking Radar antenna and aligned with the shaft of the Rotating- Antenna Pedestal. The longitudinal axis of the Radar Jamming Pod Trainer should be aligned with the shaft of the Rotating-Antenna Pedestal. Rotate the infrared receiver on the Radar Jamming Pod Trainer toward the direction from which you will use the remote controller. Install the Power Supply (Model 9609) of the Radar Jamming Pod Trainer on the shelf located under the surface of the target table. Connect the Power Supply line cord to a wall outlet. Connect the power cable of the Radar Jamming Pod Trainer to the multi-pin connector located on top of the Power Supply. G 9. On the Radar Transmitter, depress the RF POWER push button. The RF POWER ON LED should start to flash on and off. This indicates that RF power is being radiated by the Dual Feed Parabolic Antenna. 3-34

In LVRTS, turn off the AGC of the Radar Target Tracker. Turn on the Power Supply of the Radar Jamming Pod Trainer. Turn the Radar Jamming Pod Trainer on. Note that the Radar Jamming Pod Trainer status indicates that the Repeater is on. Adjust the remote controller settings to match the Radar Jamming Pod Trainer status (the Repeater is on, all else is off). G 10. Make sure the radar antenna axis is aligned with the Radar Jamming Pod Trainer. This can be done by observing the O-Scope Display of the Tracking Radar while adjusting the radar antenna orientation so that the amplitude of the Radar Jamming Pod Trainer's repeated echo signal is the same for both positions of the antenna main beam. G 11. Observing the O-Scope Display, set the Gain of the MTI Processor so that the amplitude of the Radar Jamming Pod Trainer's repeated echo signal is approximately 0.25 V. G 12. Using the remote controller, make the following adjustments to the Radar Jamming Pod Trainer: Noise.............................................. On Frequency.................................. 9.0 GHz Frequency Bandwidth......................... 0.0 GHz Frequency Modulation.......................... Triangle Attenuation 1.................................. 10 db Attenuation 2.................................. 20 db AM/Blinking......................................... Off Repeater........................................... Off RGPO.............................................. Off False Targets (FT).................................... Off The Radar Jamming Pod Trainer is now transmitting a spot noise jamming signal toward the radar antenna. G 13. Adjust the Radar Jamming Pod Trainer Noise Attenuation so that the average amplitude of the noise spikes on the O-Scope Display is approximately 0.25 V. Figure 3-15 is an example of what you should observe on the O-Scope Display once the Attenuation is adjusted. Note: Add persistence to the O-Scope Display while doing this adjustment. 3-35

Figure 3-15. Setting the average amplitude of the noise spikes on the O-Scope Display to approximately 0.25 V. G 14. Loosen the securing device found on the Radar Jamming Pod Trainer underside and rotate the Radar Jamming Pod Trainer into a slanted position of approximately 45, while observing the noise on the O-Scope Display. Tighten the securing device. How does this affect the jamming induced noise? G 15. Loosen, once again, the securing device found on the Radar Jamming Pod Trainer underside and rotate the Radar Jamming Pod Trainer to a vertical position (90 ), while observing the noise on the O-Scope Display. Tighten the securing device. How does this affect the jamming induced noise? 3-36

Briefly explain what type of polarization is used by the Radar Jamming Pod Trainer and Tracking Radar antennas, to account for the noise levels observed. Comparison Between the Effect of Cross-Polarized and Co-polarized Jamming G 16. Return the Radar Jamming Pod Trainer to the co-polarized jamming orientation. That is, loosen once again, the securing device found on the Radar Jamming Pod Trainer underside, and rotate the Radar Jamming Pod Trainer to a horizontal position (0 ). Tighten the securing device. G 17. Align the Radar Jamming Pod Trainer horn antennas with the shaft of the Rotating-Antenna Pedestal. The longitudinal axis of the Radar Jamming Pod Trainer should be aligned with the shaft of the Rotating-Antenna Pedestal. Align the radar antenna axis with the Radar Jamming Pod Trainer horn antennas. G 18. On the Radar Transmitter, disconnect the BNC-connector cable from the TRIGGER INPUT of the PULSE GENERATOR. This disables pulse transmission at the Tracking Radar, however reception is maintained. This is done so that the amplitude measurements of the radar s angular error signal, taken later on, will be due to the jamming signal only. The effects of radar clutter are thus eliminated from the measurements. G 19. In LVRTS, disconnect Oscilloscope probes 1 and 2 from TP1 and TP2 of the MTI Processor. Connect Oscilloscope probe 1 to TP27 of the Radar Target Tracker. Make the following settings on the Oscilloscope: Channel 1......................... 0.1 V/div Channel 2.............................. Off Time Base........................ 20 ms/div Set the Oscilloscope to Continuous Refresh. The Oscilloscope is now set to display the angular error signal (TP27) produced by the Tracking Radar servomechanism (see Figure 3-16). The amount by which the radar antenna turns to track a target is proportional to the angular error signal voltage. 3-37

Notice that the average value (AVG) of the voltage at TP27 (angular error signal voltage) is indicated in the Waveform Data section of the Oscilloscope (see Figure 3-16). This value should fluctuate. Figure 3-16. Angular error signal (TP27) produced by the Tracking Radar servomechanism. G 20. Familiarize yourself with Table 3-1. This table will be used to record the amplitude of the Tracking Radar s angular error signal maxima, and when it has the value of zero. That is, you will record the average value of the voltage at TP27 (angular error signal voltage), and the Radar Jamming Pod Trainer s X-axis position only when the voltage at TP27 is at a maximum or at a value of zero. In this manner, it will be possible to plot, in Figure 3-17, rough curves of the angular error signal voltage versus the position of the Radar Jamming Pod Trainer, that illustrate the Tracking Radar's response to co-polarized and cross-polarized jamming signals. 3-38

NOISE JAMMING POLARIZATION Radar Jamming Pod Trainer X-AXIS POSITION (cm) AVERAGE VALUE OF VOLTAGE AT TP27 (V) Cross-Polarized Co-Polarized Table 3-1. Average value of the voltage at TP27 (angular error signal voltage) as a function of the Radar Jamming Pod Trainer's X-axis position and jamming signal polarization. G 21. Begin the co-polarized noise jamming measurements. While observing the signal at TP27 on the Oscilloscope, slightly slide the Radar Jamming Pod Trainer along the X-axis of the target table so that the average value of the voltage at TP27 is approximately 0.00 V. While sliding the Radar Jamming Pod Trainer, attempt to maintain its target table Y-axis position at 45.0 cm, and the pointing direction of its horn antennas. When the signal at TP27 becomes approximately equal to zero, the transmit horn antenna of the Radar Jamming Pod Trainer should be aligned with the radar antenna axis. Record the average value of the voltage at TP27 and the Radar Jamming Pod Trainer s X-axis position in the first co-polarized row of Table 3-1. G 22. Once again, slide the Radar Jamming Pod Trainer along the X-axis in the direction of increasing values. Stop the displacement when the signal at TP27, being observed on the Oscilloscope, is maximum and has a positive polarity. 3-39

Record the average value of the voltage at TP27 and the Radar Jamming Pod Trainer s X-axis position in the second co-polarized row of Table 3-1. G 23. Continue sliding the Radar Jamming Pod Trainer along the X-axis in the direction of increasing values. Stop the displacement when the signal at TP27, being observed on the Oscilloscope, has returned to a value of approximately 0.00 V. Record the average value of the voltage at TP27 and the Radar Jamming Pod Trainer s X-axis position in the third co-polarized row of Table 3-1. G 24. Slide the Radar Jamming Pod Trainer along the X-axis, in the direction of decreasing values. Stop the displacement when the signal at TP27, being observed on the Oscilloscope, is maximum once again and has a negative polarity (you will pass through a positive maximum and a zero before reaching the negative maximum). Record the average value of the voltage at TP27 and the Radar Jamming Pod Trainer s X-axis position in the fourth co-polarized row of Table 3-1. G 25. Continue sliding the Radar Jamming Pod Trainer along the X-axis, in the direction of decreasing values. Stop the displacement when the voltage at TP27 has once again returned to a value of approximately 0.00 V. Record the average value of the voltage at TP27 and the Radar Jamming Pod Trainer s X-axis position in the fifth and final co-polarized row of Table 3-1. G 26. Adjust the Radar Jamming Pod Trainer orientation so as to transmit a crosspolarized noise jamming signal toward the Tracking Radar. That is, loosen the securing device found on the Radar Jamming Pod Trainer underside and rotate the Radar Jamming Pod Trainer to a vertical position (90 ). Tighten the securing device. G 27. Using the remote controller, decrease the Radar Jamming Pod Trainer s Noise Attenuation to 0 db. This adjustment will enable the cross-polarized noise jamming signal to penetrate the radar receiver system. Slowly slide the Radar Jamming Pod Trainer along the X-axis of the target positioning table so that it is aligned with the shaft of the Rotating-Antenna Pedestal. While sliding the Radar Jamming Pod Trainer, attempt to maintain its target table Y-axis position at 45.0 cm, and the pointing direction of its horn antennas. The voltage at TP27 should be approximately 0.00 V. G 28. Begin the cross-polarized noise jamming measurements. While the Tracking Radar's angular error response to a co-polarized jamming signal only had one positive-polarity maximum, one negative- 3-40

polarity maximum, and three zeroes (five measurements in all), the Tracking Radar's angular error response to a cross-polarized jamming signal has two positive-polarity maxima, two negative-polarity maxima, and 5 zeroes (nine measurements in all). To make the cross-polarized noise jamming measurements, use a procedure similar to the one outlined in procedure steps 21 to 25 for the co-polarized noise jamming measurements. That is: I. Slightly slide the Radar Jamming Pod Trainer along the X-axis of the target positioning table to find the central zero, record the average value of the voltage at TP27, and the Radar Jamming Pod Trainer's X-axis position. II. Slowly slide the Radar Jamming Pod Trainer along the X-axis, in the direction of increasing values until you locate a negative-polarity maximum, a zero, a positive-polarity maximum, and another zero. Record your measurements. Note: Change the sensitivity setting as required on the Oscilloscope. III. Slowly slide the Radar Jamming Pod Trainer along the X-axis, in the direction of decreasing values to replace the Radar Jamming Pod Trainer to the central zero position found in step I. IV. Slowly slide the Radar Jamming Pod Trainer along the X-axis, in the direction of decreasing values until you locate a positive-polarity maximum, a zero, a negative-polarity maximum, and another zero. Record your measurements. Note: If the Tracking Radar's angular error response to the crosspolarized noise jamming signal is not as expected, carefully readjust the Radar Jamming Pod Trainer orientation so that it is as near as possible to perfect orthogonality, then redo the measurements. G 29. Using the data recorded to Table 3-1, plot the Tracking Radar's angular error response curves to the co-polarized and cross-polarized noise jamming signals in Figure 3-17. Label the curves as the "radar's angular error response to co-polarized signals" and the "radar's angular error response to cross-polarized signals". 3-41

Figure 3-17. Amplitude of the radar angular error signal (TP27) as a function of the Radar Jamming Pod Trainer's X-axis position for co-polarized and cross-polarized jamming signals. 3-42

Note that the response curves which you plot in Figure 3-17 have significant differences between each other. Briefly describe the implications that this dissimilarity has on angular tracking when the radar is confronted with cross-polarized jamming. Cross-Polarization Jamming Demonstrated G 30. Slowly slide the Radar Jamming Pod Trainer along the X-axis, in the direction of increasing values to replace the Radar Jamming Pod Trainer to the central zero position found previously. The radar antenna axis should be aligned with the Radar Jamming Pod Trainer and the voltage at TP27 should be approximately 0.00 V. G 31. Enable the Tracking Radar s track-on-jamming mode by performing the following manipulations: I. Make certain that on the Radar Transmitter, the BNC-connector cable is disconnected from the TRIGGER INPUT of the PULSE GENERATOR. Thus radar pulse transmission is disabled, but reception is maintained. II. In LVRTS, set the Range Lock Disable to On. This disables automatic range tracking. III. Lock the Tracking Radar onto the cross-polarized noise jamming signal produced by the Radar Jamming Pod Trainer while observing the radar antenna. The radar locks onto the noise jamming signal but the antenna axis should be deflected away from the Radar Jamming Pod Trainer. This angular deception is due to the cross-polarized noise jamming signal. Note: If the radar antenna is still correctly aligned once the Tracking Radar is locked onto the jamming signal, slightly move the Radar Jamming Pod Trainer along the X-axis to create a small angular error. This should cause the radar antenna to move in the opposite direction, thereby producing an angular offset of a few degrees between the Radar Jamming Pod Trainer and the antenna axis direction. G 32. Make sure the DISPLAY MODE on the Antenna Controller is set to POSITION. This setting will permit you to quantitatively verify the extent of any jamming induced angle tracking errors. 3-43

What is the angular position of the radar antenna axis ( ANT. ) as indicated on the Antenna Controller? ANT. = G 33. Unlock the Tracking Radar and align the antenna axis with the Radar Jamming Pod Trainer. What is the actual angular position of the Radar Jamming Pod Trainer ( POD ) as indicated on the Antenna Controller? POD = What is the value of the angular error ( MEASURED ) induced by crosspolarization jamming? MEASURED = POD - ANT = G 34. Note that in Figure 3-17, the cross-polarized angular error response has zeroes on each side of the central zero. Note that the slope of the curve at the first zero on each side (side zero) of the central zero is of the correct sign for angular tracking. What is the average distance ( X) between each side zero and the central zero? X = cm Knowing that the Radar Jamming Pod Trainer is at a range R ( 1.25 m) from the radar antenna, calculate the angular difference ( CALCULATED ) corresponding to the average distance ( X) between the central zero and the side zeroes in the Tracking Radar's angular error response to crosspolarized signals, as illustrated in Figure 3-18. CALCULATED = = 3-44

Figure 3-18. Calculating the angular error induced by cross-polarization jamming. 3-45

G 35. Compare MEASURED and CALCULATED. Briefly explain what this implies about a radar s angular tracking when confronted by a cross-polarization jamming signal. G 36. Turn off the Tracking Radar and the Radar Jamming Pod Trainer. Disconnect all cables and remove all accessories. CONCLUSION In this exercise, you demonstrated that radar polarization agility is an effective electronic protection against jamming. However, you showed that if the radar antenna has a relatively high response to signals with a cross-polarized component, then it is vulnerable to cross-polarization jamming. Reflector-type antennas, such as the parabolic antenna, are especially vulnerable to this type of jamming. You showed that the angular error response of a radar to cross-polarized signals is significantly different than its response to co-polarized signals. This was done by measuring the amplitude of the Tracking Radar s angular error signal for different positions of the Radar Jamming Pod Trainer, transmitting either a co-polarized or a cross-polarized jamming signal. You demonstrated that when cross-polarization jamming is effective against a tracking radar, it creates a significant angular tracking offset. REVIEW QUESTIONS 1. Briefly describe the concept of polarization. 3-46

2. Briefly describe the electronic attack known as cross-polarization jamming. 3. What is radar polarization agility? 4. Does cross-polarization jamming target a specific radar design weakness or a fundamental weakness in all radars? Briefly explain. 5. Could cross-polarization jamming be effectively conducted through the sidelobes of a radar antenna? Briefly explain. 3-47