Radar Jamming and Deception - Electronic Jamming

Electronic Jamming

Electronic jamming is a form of Electronic Warfare where jammers radiate interfering signals toward an enemy's radar, blocking the receiver with highly concentrated energy signals. The two main technique styles are noise techniques and repeater techniques. The three types of noise jamming are spot, sweep, and barrage.

• Spot jamming occurs when a jammer focuses all of its power on a single frequency. While this would severely degrade the ability to track on the jammed frequency, a frequency agile radar would hardly be affected because the jammer can only jam one frequency. While multiple jammers could possibly jam a range of frequencies, this would consume a great deal of resources to have any effect on a frequency-agile radar, and would probably still be ineffective.

• Sweep jamming is when a jammer's full power is shifted from one frequency to another. While this has the advantage of being able to jam multiple frequencies in quick succession, it does not affect them all at the same time, and thus limits the effectiveness of this type of jamming. Although, depending on the error checking in the device(s) this can render a wide range of devices effectively useless.

• Barrage jamming is the jamming of multiple frequencies at once by a single jammer. The advantage is that multiple frequencies can be jammed simultaneously; however, the jamming effect can be limited because this requires the jammer to spread its full power between these frequencies, as the number of frequencies covered increases the less effectively each is jammed.

• Base jamming is a new type of Barrage Jamming where one radar is jammed effectively at its source at all frequencies. However, all other radars continue working normally.

• Pulse jamming produces noise pulses with period depending on radar mast rotation speed thus creating blocked sectors from directions other than the jammer making it harder to discover the jammer location.

• Cover pulse jamming creates a short noise pulse when radar signal is received thus conceiling any aircraft flying behind the EW craft with a block of noise.

• Digital radio frequency memory, or DRFM jamming, or Repeater jamming is a repeater technique that manipulates received radar energy and retransmits it to change the return the radar sees. This technique can change the range the radar detects by changing the delay in transmission of pulses, the velocity the radar detects by changing the doppler shift of the transmitted signal, or the angle to the plane by using AM techniques to transmit into the sidelobes of the radar. DRFM jamming can create false targets behind the EW craft but not in front of it because the jamming signal must be timed after the received radar signal. By analysing received signal strength from side and backlobes and thus getting radar antennae radiation pattern false targets can be created to directions other than one where the jammer is coming from. If each radar pulse is uniquely coded it is not possible to create targets to directions other than the direction of the jammer

• Deceptive jamming uses techniques like "range gate pull-off" to break a radar lock.