CH 9: Introduction To Radar Jamming Flashcards
Radar jamming def
Radar jamming is the intentional radiation or reradiation of radio frequency (RF) signals to interfere with the operation of a radar by saturating its receiver with false targets or false target info.
Radar jamming is one principle comp ent of electronic combat (EC). Specifically it is the electronic attack (EA) component of electronic warfare (EW).
Radar jamming is designed to counter the radar systems the play a vital role in support of an enemy IADS, with a primary purpose to create confusion and deny critical info to negate the effectiveness of enemy radar systems.
Two types of jamming
Noise jamming: produced by modulating a RF carrier wave with noise, or random amplitude changes, and transmitting that wave at the victims radar frequency. Relies on high power levels to saturate the radar receiver and deny range, and occasionally, azimuth and elevation info to the victim radar. Noise jamming takes advantage of the extreme sensitivity of the radar receiver and the transmission pattern of the radar antenna to deny critical info to victim radar.
Deception jamming: uses complex deceiving and transmitting circuits to process and retransmit jamming pulses that appear as a real target to the victim radar. A deception jammer receives the signal from the victim radar and alters the signal to provide false range, azimuth, or velocity info. The altered signal is then retransmitted. To be effective, deception jamming must match not only the victims radars operating frequency, but all other operating characteristics, including pulse repetition frequency, pulse repetition interval, pulse width, and scan rate.
Electronic support (ES) def
Another component of EW, electronic support (ES) is a component which both noise and deception jamming are heavily dependent on for threat system specific radar parametric data. ES assets update this critical info based on observed threat systems operations. This data provides the foundation for developing noise and deception jamming techniques.
Radar jamming employment options
Support jamming and self protection jamming
Support jamming can be broken down further into stand of jamming (SOJ) and escort jamming.
Support jamming def
Support jamming purpose is to create confusion and delays within the C2 structure of the IADS. Deny, delay or degrade the enemy’s ability to engage friendly forces. Support jamming ops can be focused against a national level IADS through the use of a SOJ profile or against a target area threat array using an escort jamming profile.
Stand off jamming (SOJ) def
From an orbit area outside the SAM engagement zone, SOJ aircraft employ specialized jamming techniques to deny the enemy info about the attack package. SOJ aircraft employ specialized noise jamming techniques to generate jamming strobes on the victim radar display. This effectively denies range and azimuth info on aircraft ingressing and egressing the area covered by noise jamming strobes. Effectiveness of SOJ jamming is determined by the power the hammer can generate relative to the power the victim radar can generate. This Is called the jamming-to-signal (J/S) ratio.
False target jamming def
SOJ aircraft can also employ a deception technique to generate false targets to confuse the radar operator and mask the presence of real targets. In this specialized technique, the deception jammer must tune to the frequency, PRF, and scan rate of victim radar. The jammer then transmits multiple jamming pulses that the victim radar receiver proceeded like real target returns. False moving targets and false range targets are generated by varying the time delay of the jamming pulses based on the PRF and scan rate of victim radar.
Escort jamming def
Escort jamming was a specific tactic used by the EA-6B Prowler. The EA-6B was employed as an integral part of the attack package and is normally positioned behind and above the attack package.
Using noise jamming, the EA-6B attempts to deny range and azimuth info to the victim radar by injecting high power signals into the main radar beams and sidelobes. To be effective, the WA-6B must be properly positioned in relation to the ingressing or egressing attacks package.
Self protection radar jamming def
Self protection radar jamming targets the radar systems that support jamming cannot negate. They are part of a self protection suite that includes a self protection jamming pod, a chaff/flare dispenser, and on some aircraft, a towed decoy system.
The overall purpose is individual aircraft survivability. They employ deception jamming techniques against the TTRs associated with SAM, AAA, and AI assets and are designed to break radar track or generate sufficient tracking errors to cause the missile or bullet to miss aircraft.
Advantages of self protection radar jamming systems employing deception jamming techniques
- Effective deception jamming techniques usually require less power than noise jamming techniques
- Less power means less weight and space
- Deception jammer scan be designed to jam multiple threats, which is critical for ops in a dense threat environment.
Disadvantages of deception jamming techniques for self protection jamming
- Deception jammers are complex electronic systems that must receive a victim radars signal, memorize all characteristics, modify the signal, and retransmit this modified signal at a high power level.
- To be effective, deception jammers must be programmed with all the signal parameters (freq, PRF, PRI, pulse width, scan rate etc) of the victim radar.
- Because many deception techniques can be effective against specific threats, selecting optimum techniques to employ against these threats must be based on identified threat system limitations which may be difficult to identify.
Fundamentals of radar jamming
Principles that apply to all types of jamming and to all jamming employment options. They include frequency matching, continuous interference, signal to noise ratio, jamming to signal ratio, and burn through range.
Frequency matching def
Radar jamming systems must transmit signals at the frequency of the victim radar. This applies to both noise and deception jamming. If a jamming signal does not match the transmitter frequency, the jamming signal is not received and displayed on the scope. When a jamming signal matches the transmitter frequency, the jamming signal is revived and masks the target display.
Continuous interference def
For max effectiveness, a jamming transmitter should produce continuous interference. Intermittent jamming on a radar scope may not completely mask the target. While true for noise jamming techniques, continuous interference also applies to deception techniques, especially when target reacquisition is considered.
Signal to noise (S/N) ratio def
False alarm def
Signal to noise (S/N) ratio is a measure of the ability of the victim radar to detect targets. It is also an indication of the vulnerability of the radar to certain jamming techniques, especially noise jamming.
The radar receiver amplifies both target signal and thermal noise and the output of the radar receiver will contain the target signal and the noise amplified across the bandwidth of the receiver. Separating the desired target signal from the undesired noise signal is one of the major problems for radar designers.
The lack of discrimination between noise and target returns because of a poor S/N ratio can result in designating fluctuations in the noise level as actual target signals, known as false alarms.
For any target return to be detected by the radar, the S/N ratio must be greater than one. If the S/N ratio is less than one, the target will not be detected above the receiver noise level.
