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Projecte llegit

Títol: Radar jamming prevention through sidelobes nulling

Estudiants que han llegit aquest projecte:

Director/a: ÚBEDA FARRE, EDUARD

Departament: TSC

Títol: Radar jamming prevention through sidelobes nulling

Data inici oferta: 06-02-2020     Data finalització oferta: 06-10-2020


Estudis d'assignació del projecte:
    GR ENG SIST AEROESP
Tipus: Individual
 
Lloc de realització: EETAC
 
Paraules clau:
sidelobe nulling, array factor, radar jamming, electronic countermeasures
 
Descripció del contingut i pla d'activitats:
Radar systems obtain the location and velocity of a target (typically aircrafts or ships) by processing the scattered electromagnetic echo after emitting an electromagnetic signal. Track-Radars are able to follow a target in motion. In general, Radar systems provide intelligence to organize the defense/attack of a determined area under surveillance. Therefore, any surveillance Radar system must be designed such that the provided information is reliable. Specific Electromagnetic-wave transmitters, so- called jammers, are designed to interfere with the proper behavior of a track or surveillance Radar. They setup strategies to deceive or damage the adequate performance of Radars. The strategies for jamming are mechanical when fake targets are created on purpose to capture the attention of the Radar; the jamming is electronic when EM signals are sent to deceive the Radar system. The latter is normally called Electronic warfare or, more specifically, Electronic countermeasures (ECM). The Radar develops its own strategies to block the electronic attacks through the so-called Electronic counter countermeasures (ECCM).
A pioneering manner to block the normal performance of a pulsed Radar system is to send an energetic Continuous wave (CW) signal that the Radar receives through a side lobe. Also, the interfering signal may be pulsed and synchronized with the Pulse Repetition interval of the Radar in order to make appear a non-existent target. A straightforward manner to block these signals is to impose a zero of radiation/reception in the radiation pattern of the Radar system, which of course requires the previous detection of the direction of arrival of the interference. In track-Radars, the antenna is normally implemented through an array to allow for a versatile beamforming. In this cases, the side lobe nulling technique involves the re-computation in real-time of a set of array-feeding coefficients so that a zero in the radiation pattern arises in the direction of arrival of the jamming signal. Of course, these new coefficients are also constrained to keep the main lobe aligned over the same direction of observation. There exist several strategies to establish these new coefficients; a simple scheme relies only on the modification of the phases of some coefficients. However this scheme is not always successful, whereby a direct computation of some coefficients may be adequate instead. In this work several techniques of side lobe nulling will be implemented. The actual error on the original pattern will be assessed in terms of the number and location of the array coefficients that are modified. In principle, the work will be carried out on the basis of the knowledge of the carried frequency of the jamming signal. A manner to avoid a single-frequency jamming is a frequency-hoping strategy. In this case, the jammers set up a wideband jamming. The prevention through the side lobe nulling becomes then more elaborate, which will be studied in this project too.
 
Overview (resum en anglès):
Electronic Warfare plays nowadays a crucial role in the design of attack, defence or security strategies because of the important presence of systems that make use of the electromagnetic spectrum. Thus, controlling enemy¿s radiocommunications or interfering with their detection systems is a key point to gain hegemony.

Since early 20th century, Electronic Warfare techniques have been developed by governments, thereby creating different types of jamming and deception techniques to interfere with the enemy¿s spectrum. In this work, mechanical jamming, noise jamming or electronic deception schemes -in the frame of the so-called Electronic Countermeasures (ECM) - are outlined to understand the importance of the Electronic Warfare. Other existing jamming techniques have not been revealed because they are classified by governments.

This work focuses on one particular ECM strategy of electronic jamming or deception; namely, attacking the surveillance radar through observation angles along the sidelobes of the Radar radiation pattern. This may be done by sending noise, which raises the threshold detection to maintain the false-alarm probability constant, or by sending pulses that simulate the presence of a target, causing a wrong angle capture associated with the real target [1]. As the attack is carried out through a sidelobe, the Radar operator may not be able to detect this jamming until it is too late.

The several known jamming techniques require the establishment of defensive techniques, so-called Electronic Counter-Countermeasures (ECCM), to preserve the proper performance of the Radar system. Some well-established ECCM strategies arise for example from the agile modification of the working frequency or from filtering out ¿ almost - still targets in the surveillance scene. In this work, we focus on the sidelobe cancellation technique, which excels as an ECCM scheme to prevent jamming through the sidelobes of the radiation pattern. The Radar surveillance system can find out the impinging direction of the jamming signal thanks to a Radio Direction Finder. This allows the insertion of preventive zeros in the radiation pattern over the frequency range of performance. If required, several null radiation directions can be assigned also if several jammers attach simultaneously over several jamming directions. Each different working frequency (under given jamming direction) or each jamming angular incidence - for a fixed frequency - implies a different position of the zero location in the array radiation pattern. The goal of this work is to adapt the sidelobe cancellation method described in [2] to a Matlab code and to identify the test cases where this method is most successful.

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