JED - January 2010 - (Page 44)

EW 101 EW Against Modern Radars – Part 2 Radar Jamming Techniques By Dave Adamy TThe Journal of Electronic Defense | January 2010 his month, we will review jamming techniques. These techniques can be divided into cover and deceptive jamming. The jamming effectiveness of both types of techniques is stated in terms of jamming-to-signal ratio (J/S) as discussed last month. Cover Jamming The object of cover jamming is to reduce the quality of the signal in the radar’s receiver enough that the radar cannot acquire or track its target. It can be used in either self-protection or remote-jamming geometry. Cover jamming usually has a noise waveform, but sometimes other waveforms are used to overcome electronic protection (EP) features of the radar. These EP techniques will be covered later in this series. The equations for J/S and burn-through presented last month assumed that all of the jammer’s power was within the bandwidth of the radar receiver. If a jammer uses noise that is wider in frequency than the effective bandwidth of the radar receiver, only the part that is within the radar’s receiver bandwidth is effective. Jamming efficiency is the total jammer effective radiated power (ERP) divided by the effective jammer ERP. This is equal to the radar receiver bandwidth divided by the jamming bandwidth. For example, if the radar receiver bandwidth is 1 MHz and the jamming signal bandwidth is 20 MHz, the jamming efficiency is 5 percent. is tuned to the radar broadcast frequency – this is called spot jamming. As shown in Figure 1, spot jamming wastes little of its jamming power, so the jamming efficiency is increased significantly. Spot width is enough to cover the uncertainty in target signal and set-on frequencies. (We will cover coherent jamming in a later column.) Efficiency is still the radar bandwidth divided by the jamming bandwidth – but the ratio is more favorable. Dr. Schleher, in his book Electronic Warfare in the Information Age, defines spot jamming as jamming over a bandwidth less than five times the radar’s bandwidth. JAMMER RECEIVER LISTENING NOISE COVERAGE FREQUENCY UNCERTAINTY TIME Figure 1: Spot Jamming concentrates noise around the radar’s operating frequency. Swept Spot Jamming If a narrowband jammer is swept across all of the frequency range that is expected to contain threat signals, as shown in Figure 2, it is called a swept spot jammer. The swept spot jam- Barrage Jamming Barrage jamming is generated by a wideband jammer that broadcasts noise over a whole band of frequencies that is expected to contain one or more threat radars. This technique was frequently used in early jammers, and is still an appropriate approach for many jamming situations. The great advantage of barrage jamming is that it does not require real-time information about radar operating frequencies. Look-through (i.e., interruption of jamming to look for threat radar signals) is not necessary. The problem is that barrage jamming typically has very low jamming efficiency. Most of the jamming power is wasted because the effective J/S is reduced by the efficiency factor, and the burn-through range is correspondingly increased. Swept Spot Jamming FREQUENCY Spot Jamming When the bandwidth of the jamming signal is reduced to a little more than the target radar bandwidth and the jammer Fi 2 S tS tJ i TIME j i b d th h l b di Figure 2: Swept Spot Jamming moves a narrow jamming band across the whole band in which the radar might operate.

Table of Contents for the Digital Edition of JED - January 2010

JED - January 2010
Contents
The View From Here
Calendar
From the President
The Monitor
Washington Report
World Report
Asia-Pacifi c EW: All Eyes on China?
Maneuver in the EM Domain
Technology Survey: Surface Naval Expendables and Launchers
EW 101
AOC Industry/Institute/University Members
Index of Advertisers
JED Sales Offices

JED - January 2010

https://www.nxtbook.com/naylor/JEDM/JEDM0318
https://www.nxtbook.com/naylor/JEDM/JEDM0218
https://www.nxtbook.com/naylor/JEDM/JEDM0118
https://www.nxtbook.com/naylor/JEDM/JEDM1217
https://www.nxtbook.com/naylor/JEDM/JEDM1117
https://www.nxtbook.com/naylor/JEDM/JEDM1017
https://www.nxtbook.com/naylor/JEDM/JEDM0917
https://www.nxtbook.com/naylor/JEDM/JEDM0817
https://www.nxtbook.com/naylor/JEDM/JEDM0717
https://www.nxtbook.com/naylor/JEDM/JEDM0617
https://www.nxtbook.com/naylor/JEDM/JEDM0517
https://www.nxtbook.com/naylor/JEDM/JEDM0417
https://www.nxtbook.com/naylor/JEDM/JEDM0317
https://www.nxtbook.com/naylor/JEDM/JEDM0217
https://www.nxtbook.com/naylor/JEDM/JEDM0117
https://www.nxtbook.com/naylor/JEDM/JEDM1216
https://www.nxtbook.com/naylor/JEDM/JEDM1116
https://www.nxtbook.com/naylor/JEDM/JEDM1016
https://www.nxtbook.com/naylor/JEDM/JEDM0916
https://www.nxtbook.com/naylor/JEDM/JEDM0816
https://www.nxtbook.com/naylor/JEDM/JEDM0716
https://www.nxtbook.com/naylor/JEDM/JEDM0616
https://www.nxtbook.com/naylor/JEDM/JEDM0516
https://www.nxtbook.com/naylor/JEDM/JEDM0416
https://www.nxtbook.com/naylor/JEDM/JEDM0316
https://www.nxtbook.com/naylor/JEDM/JEDM0216
https://www.nxtbook.com/naylor/JEDM/JEDM0116
https://www.nxtbook.com/naylor/JEDM/JEDM1215
https://www.nxtbook.com/naylor/JEDM/JEDM1115
https://www.nxtbook.com/naylor/JEDM/JEDM1015
https://www.nxtbook.com/naylor/JEDM/JEDM0915
https://www.nxtbook.com/naylor/JEDM/JEDM0815
https://www.nxtbook.com/naylor/JEDM/JEDM0715
https://www.nxtbook.com/naylor/JEDM/JEDM0615
https://www.nxtbook.com/naylor/JEDM/JEDM0515
https://www.nxtbook.com/naylor/JEDM/JEDM0415
https://www.nxtbook.com/naylor/JEDM/JEDM0315
https://www.nxtbook.com/naylor/JEDM/JEDM0215
https://www.nxtbook.com/naylor/JEDM/JEDM0115
https://www.nxtbook.com/naylor/JEDM/JEDM1214
https://www.nxtbook.com/naylor/JEDM/JEDM1114
https://www.nxtbook.com/naylor/JEDM/JEDM1014
https://www.nxtbook.com/naylor/JEDM/JEDM0914
https://www.nxtbook.com/naylor/JEDM/JEDM0814
https://www.nxtbook.com/naylor/JEDM/JEDM0714
https://www.nxtbook.com/naylor/JEDM/JEDM0614
https://www.nxtbook.com/naylor/JEDM/JEDM0514
https://www.nxtbook.com/naylor/JEDM/JEDM0414
https://www.nxtbook.com/naylor/JEDM/JEDM0314
https://www.nxtbook.com/naylor/JEDM/JEDM0214
https://www.nxtbook.com/naylor/JEDM/JEDM0114
https://www.nxtbook.com/naylor/JEDM/JEDM1213
https://www.nxtbook.com/naylor/JEDM/JEDM1113
https://www.nxtbook.com/naylor/JEDM/JEDM1013
https://www.nxtbook.com/naylor/JEDM/JEDM0913
https://www.nxtbook.com/naylor/JEDM/JEDM0813
https://www.nxtbook.com/naylor/JEDM/JEDM0713
https://www.nxtbook.com/naylor/JEDM/JEDM0613
https://www.nxtbook.com/naylor/JEDM/JEDM0513
https://www.nxtbook.com/naylor/JEDM/JEDM0413
https://www.nxtbook.com/naylor/JEDM/JEDM0313
https://www.nxtbook.com/nxtbooks/naylor/JEDM0213
https://www.nxtbook.com/nxtbooks/naylor/JEDM0113
https://www.nxtbook.com/nxtbooks/naylor/JEDM1212
https://www.nxtbook.com/nxtbooks/naylor/JEDM1112
https://www.nxtbook.com/nxtbooks/naylor/JEDM1012
https://www.nxtbook.com/nxtbooks/naylor/JEDM0912
https://www.nxtbook.com/nxtbooks/naylor/JEDM0812
https://www.nxtbook.com/nxtbooks/naylor/JEDM0712
https://www.nxtbook.com/nxtbooks/naylor/JEDM0612
https://www.nxtbook.com/nxtbooks/naylor/JEDM0512
https://www.nxtbook.com/nxtbooks/naylor/JEDM0412
https://www.nxtbook.com/nxtbooks/naylor/JEDM0312
https://www.nxtbook.com/nxtbooks/naylor/JEDM0212
https://www.nxtbook.com/nxtbooks/naylor/JEDM0112
https://www.nxtbook.com/nxtbooks/naylor/JEDM1211
https://www.nxtbook.com/nxtbooks/naylor/JEDM1111
https://www.nxtbook.com/nxtbooks/naylor/JEDM1011
https://www.nxtbook.com/nxtbooks/naylor/JEDM0911
https://www.nxtbook.com/nxtbooks/naylor/JEDM0811
https://www.nxtbook.com/nxtbooks/naylor/JEDM0711
https://www.nxtbook.com/nxtbooks/naylor/JEDM0611
https://www.nxtbook.com/nxtbooks/naylor/JEDM0511
https://www.nxtbook.com/nxtbooks/naylor/JEDM0411
https://www.nxtbook.com/nxtbooks/naylor/JEDM0311
https://www.nxtbook.com/nxtbooks/naylor/JEDM0211
https://www.nxtbook.com/nxtbooks/naylor/JEDM0111
https://www.nxtbook.com/nxtbooks/naylor/JEDM1210
https://www.nxtbook.com/nxtbooks/naylor/JEDM1110
https://www.nxtbook.com/nxtbooks/naylor/JEDM1010
https://www.nxtbook.com/nxtbooks/naylor/JEDM0910
https://www.nxtbook.com/nxtbooks/naylor/JEDM0810
https://www.nxtbook.com/nxtbooks/naylor/JEDM0710
https://www.nxtbook.com/nxtbooks/naylor/JEDM0610
https://www.nxtbook.com/nxtbooks/naylor/JEDM0510
https://www.nxtbook.com/nxtbooks/naylor/JEDM0410
https://www.nxtbook.com/nxtbooks/naylor/JEDM0310
https://www.nxtbook.com/nxtbooks/naylor/JEDM0210
https://www.nxtbook.com/nxtbooks/naylor/JEDM0110
https://www.nxtbook.com/nxtbooks/naylor/JEDM1209
https://www.nxtbook.com/nxtbooks/naylor/JEDM1109
https://www.nxtbook.com/nxtbooks/naylor/JEDM1009
https://www.nxtbook.com/nxtbooks/naylor/JEDM0909
https://www.nxtbook.com/nxtbooks/naylor/JEDM0809
https://www.nxtbook.com/nxtbooks/naylor/JEDM0709
https://www.nxtbook.com/nxtbooks/naylor/JEDM0609
https://www.nxtbook.com/nxtbooks/naylor/JEDM0509
https://www.nxtbook.com/nxtbooks/naylor/JEDM0409
https://www.nxtbook.com/nxtbooks/naylor/JEDM0309
https://www.nxtbook.com/nxtbooks/naylor/JEDM0209
https://www.nxtbook.com/nxtbooks/naylor/JEDM0109
https://www.nxtbook.com/nxtbooks/naylor/JEDM0908
https://www.nxtbookmedia.com