Using Cross-Eye Techniques to Counter Radio Frequency Agile Monopulse Processing

The purpose of this research was to evaluate how current cross-eye techniques protect an airborne platform versus a pulse-to-pulse Radio Frequency (RF) agile monopulse processing threat and, if necessary, develop a new cross-eye techniques to counter this threat. This research evaluates how both current retrodirective cross-eye techniques and an original technique, namely synchronized cross-eye, hide the true skin return in the time and frequency domain while preserving the necessary phase interferometric effects at the threat radar location. Existing retrodirective cross-eye techniques are inadequate to counter the RF agile threat due to propagation delays. Using modeling and simulation, the research shows that geometrically dependent parameters are virtually constant on a pulse-to-pulse basis. If a low Radar Cross Section source can be deployed and, given that it is illuminated first by the threat radar, cross-eye jamming waveforms at the threat can hide the skin return in time and reproduce the necessary phase interferometric pattern, but small frequency differences between the two jamming sources occur at the threat radar location. Fortunately, these differences can only be detected if the threat employs up-front Doppler processing. Monopulse processing radars are a true threat to airborne platforms. Existing countermeasure techniques may not be able to deal with a monopulse processing radar with random, pulse-to-pulse Radio Frequency (RF) agility. This thesis examines the effects current cross-eye techniques have against RF agile threats and investigates an alternative form of cross-eye, synchronized cross-eye, to counter RF agile threats

Statistical skin-return results for retrodirective cross-eye jamming

The effect of the radar skin return from the platform on which a cross-eye jammer is mounted is significant in many practical cross-eye jamming scenarios. However, all published analyses of skin-return affected cross-eye jamming have significant limitations. These limitations are addressed by deriving equations for the distribution of the cross-eye gain in the presence of skin return. The values of these results are demonstrated by using them to gain insight into how skin return affects cross-eye jamming.The National Research Foundation of South Africa (Grant number 119151).http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?reload=true&punumber=7hj2019Electrical, Electronic and Computer Engineerin

Cross-eye gain in multiloop retrodirective cross-eye jamming

The simultaneous use of multiple retrodirective cross-eye jammers is analysed for both the case where the jammer loops point in different directions and when they point in the same direction. In both cases, the use of multiple cross-eye jammer loops is shown to lead to significantly increased angular errors in the threat radar under certain conditions. Alternatively, the sum-channel return can be increased to reduce the jammer-to-signal ratio (JSR) requirements for each jammer loop.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?reload=true&punumber=7hb2016Electrical, Electronic and Computer Engineerin

Limiting apparent target position in skin-return influenced cross-eye jamming

It is desirable to limit the apparent target to one side of a retrodirective cross-eye jammer despite the variation caused by platform skin return. The relationship between the jammer parameters and the jammer-to-signal ratio (JSR) to ensure that this occurs is investigated. When this relationship is not satisfied, the proportion of the apparent targets generated on the opposite side of the jammer is determined.This work was supported by the Armaments Corporation of South Africa (Armscor) under Contract KT521896.http://ieeexplore.ieee.org/arnumber=6558044hb201

Statistical skin-return results for retrodirective cross-eye jamming

The effect of the return from the platform on which a cross-eye jammer is mounted is significant in many practical cross-eye jamming scenarios. However, all published analyses of skin-return affected cross-eye jamming have significant limitations. These limitations are addressed by deriving equations for the distribution of the cross-eye gain in the presence of skin return. The value of these results is demonstrated by using them to gain insight into how skin return affects cross-eye jamming.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?reload=true&punumber=7hb2017Electrical, Electronic and Computer Engineerin

The practical implementation of a retrodirective cross-eye jammer by using software defined radio (SDR)

Dissertation (MEng (Electronic Engineering))--University of Pretoria, 2022.Radar-guided missiles have the potential to cause extreme damage to vital military assets. Although traditional deception techniques can deceive radars in range and Doppler shift, only a few methods can deceive them in angle. Cross-eye jamming was identified as a possible countermeasure against angular radar threats. This electronic attack (EA) method works by artificially creating the worst case of glint in angular radars. Numerous analyses of cross-eye jamming exist in the literature. The earlier analyses were derivative glint analyses that made two incorrect assumptions. The first was to use linear fits to the monopulse antenna patterns, which is only valid when the target platform is on broadside of the radar. The second was to assume that the target platform is an infinite distance from the radar, which is not possible. The analyses also did not consider retrodirectivity. It was only during a later cross-eye jamming analysis that the limitations were identified and corrected. The limitations in the analysis could have been identified much sooner if practical measurements were made. The extended cross-eye jamming analysis made fewer assumptions and was proven accurate by numerous simulations and some experimental results. However, the only available experiments where the radar rotation was considered did not implement true retrodirectivity but simulated it by combining isolated channel measurements. A need was identified for the development of a truly-retrodirective cross-eye jammer in a laboratory environment to expand the body of knowledge available about cross-eye jamming. The cost-effective jammer would be used to identify any real-world effects or anomalies that could not be predicted by the extended analysis or identified by simulation. This dissertation presents the development of a truly-retrodirective cross-eye jammer by using a software-defined radio (SDR). The development is accompanied by a method of calibrating the cross-eye jammer to obtain the ideal magnitude factor and phase difference between the retrodirective paths by minimising the magnitude of the sum-channel return of a monopulse radar. The developed system was tested in an anechoic environment against a self-implemented phase-comparison monopulse radar. It was shown that significant angular errors could be induced. The angular errors were larger than 10° at broadside of the radar. This equated to a minimum miss-distance of around 1 m at a range of 6 m. It was shown that a cross-eye gain of around ten was obtained, which resulted in the indicated angle of the radar never becoming zero, regardless of the radar rotation. This suggested that tracking radars, such as that used by active homing missiles, would lose lock on the target platform. Further experiments also proved the jammer to be retrodirective, with large angular errors for all rotations of the jammer antennas. All results correlated very well with that predicted by the extended analysis, with only minor deviations between radar rotations of 0° and 5°. After further investigation, it was concluded that the deviations were most likely caused by mutual coupling between the radar antennas and were not caused by a reduction in the performance of the jammer.Electrical, Electronic and Computer EngineeringMEng (Electronic Engineering)Unrestricte

A comprehensive investigation of retrodirective cross-eye jamming

Cross-eye jamming is an Electronic Attack (EA) technique that induces an angular error in the radar being jammed. The main benefit of cross-eye jamming is that it is effective against monopulse tracking radars, which are largely immune to other forms of jamming. The objective of this research is to gain a complete understanding of cross-eye jamming so that systems that might be developed in future can be properly specied. The main contribution of this work is a comprehensive mathematical and experimental study of retrodirective cross-eye jamming. The mathematical analysis considers all aspects of an isolated, single-loop, retrodirective cross-eye jamming engagement, thereby avoiding the approximations inherent in other cross-eye jamming analyses. Laboratory experiments that accurately represent reality by using the radar for both transmission and reception, and simulating a true retrodirective cross-eye jammer were performed to validate the theoretical analysis. Lastly, the relationship between the angular error induced in the radar being jammed and the matching required from a cross-eye jammer system is explored. The most important conclusion of this work is that the traditional analyses of cross- eye jamming are inaccurate for the conditions under which cross-eye jammers operate. These inaccuracies mean that the traditional analyses are overly conservative, particularly at short ranges and for high cross-eye gains, suggesting that practical cross-eye jammers can be realised more easily than is generally believed.Thesis (PhD)--University of Pretoria, 2010.Electrical, Electronic and Computer Engineeringunrestricte

Implementation and testing of a retrodirective cross-eye jammer

One of the few electronic attack techniques that can deceive radars in angle is cross-eye jamming, which mimics the naturally-occurring phenomenon glint. The extreme tolerance requirements of cross-eye jamming mean that a retrodirective implementation is required, but published measurements of cross-eye jamming either ignore the retrodirective implementation or only simulate it. The implementation of a retrodirective cross-eye jammer and its testing against a monopulse radar are described. A procedure for calibrating the jammer is outlined and is shown to be effective by achieving large angular errors. The measured results agree well with the extended analysis of cross-eye jamming and confirm that the implemented jammer is retrodirective. Specifically, the ability of a cross-eye jammer to generate an indicated angle that never becomes zero, thereby potentially breaking a tracking lock, is confirmed.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?reload=true&punumber=7hj2023Electrical, Electronic and Computer Engineerin

Phase‐conjugating retrodirective cross‐eye jamming

A cross‐eye jammer based on a phase‐conjugating (PC) retrodirective array is proposed. Such PC cross‐eye jammers eliminate the delay inherent in traditional Van‐Atta (VA) cross‐eye jammers and induce errors in radars that use the same antenna beam for transmission and reception, while VA cross‐eye jammers do not. Validated simulations are provided to confirm the effectiveness and retrodirective properties of the PC cross‐eye jammer.https://ietresearch.onlinelibrary.wiley.com/journal/1350911xhj2021Industrial and Systems Engineerin

Analysis of path-length effects in multiloop cross-eye jamming

The effect of path-length differences on multiloop retrodirective cross-eye jammers is evaluated. It is shown that such jammers may act as beacons, and the conditions under which this occurs are investigated for two-loop jammers. The sensitivity of the two-loop cross-eye gain to path-length differences is also studied and is found to be small for small path-length differences, but to increase rapidly. The effect of the two-loop cross-eye jammer parameters on path-length effects is also considered.The National Research Foundation of South Africa (NRF) [85845http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?reload=true&punumber=7hj2017Electrical, Electronic and Computer Engineerin