JED - May 2010 - (Page 69)
EW Against Modern Radars – Part 6
Radar Electronic Protection
lthough electronic protection (EP) is one of the subﬁelds of electronic warfare, it is unlike electronic support (ES) or electronic attack (EA) in that it does not typically involve speciﬁc EW hardware. It is, rather, a number of features of sensor systems which are designed to reduce the effectiveness of enemy jamming. Thus, we say that EP does not protect your platform, but rather protects your sensors. We discussed EP techniques to protect communication systems in the May to October 2009 “EW 101” columns. Now, we will cover Radar EP.
Table 1 lists the principal radar EP techniques and the EA techniques against which they provide protection.
and provide anti-jamming protection as an additional benefit. As we go through these techniques, you will note that the amount of anti-jam protection depends on the details of the implementation and that some techniques attack more than one type of jamming.
The Journal of Electronic Defense | May 2010
A text book recommended for those who want to go into the math behind electronic protection techniques is Electronic Warfare in the Information Age by Dr. Curtis Schleher (1999, Artech House, ISBN: 0-89006-526-8). Another text that is very helpful in understanding radar operation is Introduction to Airborne Radar Second Edition by George Stimson (1998, SciTech, ISBN: 1-891121-01-4).
1: ELECTRONIC PROTECTION TECHNIQUES
Protect Against Radar detection & side-lobe jamming Side-lobe noise jamming Side-lobe pulse jamming Cross-pol jamming Decoys & Non-coherent jamming Many deceptive jamming techniques Chaff & non-coherent jamming Range gate pull-off AGC jamming All types of jamming Ultra-low Side Lobes Side Lobe Cancellation Side Lobe Blanking Anti-Cross Pol Pulse Compression Mono-pulse Radar Pulse Doppler Radar Leading Edge Tracking Dicke-Fix Burn-through Modes Frequency Agility PRF Jitter Home on Jam Modes
Ultra-Low Side Lobes
Figure 1 shows the gain pattern of a typical radar antenna. Note that the angular variation of gain is shown in two views. The top view is a polar plot of gain vs. angle. If you go to an antenna manufacturer’s website and look up the gain pattern for a specific antenna you will see a family of curves like this. The curves are generated by placing the antenna in an anechoic chamber and rotating it on a turntable. There is a carefully calibrated transmitting antenna in a conical section of the chamber and all of the chamber’s surfaces are covered with radio absorptive material. Thus, the antenna on the turntable only receives direct waves from the transmitter. All reflections from the antenna and elsewhere are absorbed at the chamber walls. If the antenna under test is rotated 360 degrees in the horizontal plane, the resulting received power level is propor-
Main Beam Bore-sight Gain
All types of jamming
Side Lobe Gain Side Lobe Isolation
Range gate pull in and cover pulses All types of jamming
As we discuss each of these techniques, it will be necessary to get into related subjects, such as the way the radar processes data. You will also see that what we are calling “EP techniques” are sometimes incorporated in radars for other reasons
Angle from Bore-sight
Figure 1: Antenna side lobes allow radar detection and jamming from any direction.
Table of Contents for the Digital Edition of JED - May 2010
JED - May 2010
The View From Here
From the President
The Future for Airborne Expendables
Protecting Low-Cost and Non-Traditional Platforms
Technology Survey: Missile Warning Systems
JED Sales Offices
Index of Advertisers
JED Quick Look
JED - May 2010