Jamming Effect Research Articles

The architecture and technology of cognitive electronic warfare

Development and applications of technologies of cognitive radio, software-defined network, cognitive network as well as anti-jamming and low intercept probability in radar and other communication systems have led to an exponential increase in the complexity of the electromagnetic environment. When confronted with the challenges in the future complicated battlefield environment, how to speed up the loop of “observe-orient-decide-act (OODA)” and realize electromagnetic agility is the key problem for electronic warfare system. To make the system more cognitive, we combine the theory of artificial intelligence with electronic warfare, which can significantly enhance the ability to sense a threat signal, make a jamming decision, and evaluate the jamming effect. Moreover, this will shorten the reaction time to unknown threats, speed up the OODA loop, and strengthen the operational capability of the system.

New method based on Solid Phase Microextraction and Multidimensional gas chromatography-mass spectrometry to determine pesticides in strawberry jam

Although, the use of pesticides is necessary in agriculture to prevent crops destruction and to avoid the attack to leaves and stems of the plants, which cause quality defects of fruits and yield reduction, the control of pesticide is important in order to guarantee human safety. In the present study, a new method based on the use of solid-phase microextraction (SPME) followed by multidimensional gas chromatography-mass spectrometry (MDGC-MS) analysis was developed to detect pesticides in strawberry jam. Commercial and home-made jams as well as spiked non-spiked samples were included in the study. The method was validated by analysing commercial jam samples spiked with a pesticide mixture (ie, standard Mix 101). As a result, Relative Standard Deviation estimated from five replicates, was always below 16%. Limit detection values varied from 0.11 to 0.42 ng/kg on the first dimension and from 0.013 to 0.093 ng/kg on the second dimension. These levels are considerably lower than the Maximum Residue Levels established for strawberry pesticides by EU Regulations. Also, the matrix effect of the strawberry jam on the effectiveness of the SPME extraction was evaluated. The data presented demonstrate that the method proposed is capable of detecting reliably very low concentrations of pesticides in strawberry jams between 0.013 and 0.093 ng/kg. Additional advantages of the method are its repeatability, rapidity, simplicity, selectivity and environmental friendly nature.

A Deception Jamming Method Countering Bi- and Multistatic ISAR Based on Micro-Doppler Effect

Bi- and multistatic inverse synthetic aperture radar (ISAR) operate with spatially separated transmitting and receiving antennas. A deception jamming method countering bi- and multistatic ISAR is proposed in this paper based on the study of micro-Doppler effect. The jammer modulates the intercepted ISAR signals with added micro-Doppler information and retransmits them to the real target, which scatters the jamming signals to the radar receivers. Deceptive false-target images with interference bands in the cross-range direction will be induced by the jamming signals through the imaging process of radar receivers. Additionally, real-time movement features of the false-targets can be flexibly adjusted by changing the modulation parameters, which improves the fidelity of the false-targets. The equivalent number of looks (ENL) index is used to evaluate the jamming effects. Simulation results validate our theoretical analysis and show the effectiveness and practicability of our method.

The effect of surface grafting polymer chains on the shear thickening of hard microsphere suspensions

Shear thickening of suspensions was generally researched as a macro-perspective, the neglect of microstructure and micro-interactions may deviate the truth. Here, four suspensions were prepared by matching SiO2 microspheres, SiO2-g-PMMA microspheres with oligomeric fluids PEG, PPG, respectively, the rheological behavior of them under the controlled temperature was investigated to figure out the influence of grafted chains on shear thickening. For all suspensions, the reversible shear thickening with significant temperature dependency was observed, the critical shear rate (γ˙) decreases rapidly and reaches to a balance with the decreased temperature. Under the same media viscosity, the γ˙ of SiO2/PEG suspensions is higher than that of other suspensions at the lower temperature due to the stronger hydrogen bond interaction between the hydroxyl of microsphere and media. Comparing PEG, using low polar PPG as media raises the γ˙of SiO2 suspensions and decreases the γ˙ of SiO2-g-PMMA suspensions by reason of the changed interaction between microsphere and media, which is also affected by temperature. Moreover, the critical shear stress (τc) of SiO2/PEG suspensions is higher than that of other suspensions in all test temperature region, revealing that the grafted chains weaken the jamming effect. Two models were used to predict τc, the Wagner’s hard-sphere model predicts the SiO2/PEG suspensions well, Kaldasch’s model based on polymer stabilized colloidal system could fit the SiO2-PMMA/PEG suspensions better.

Engineering the emission of laser arrays to nullify the jamming from passive obstacles

Non-Hermitian characteristics accompany any photonic device incorporating spatial domains of gain and loss. In this work, a one-dimensional beam-forming array playing the role of the active part is disturbed from the scattering losses produced by an obstacle in its vicinity. It is found that the placement of the radiating elements leading to perfect beam shaping is practically not affected by the presence of that jammer. A trial-and-error inverse technique of identifying the features of the obstacle is presented based on the difference between the beam target pattern and the actual one. Such a difference is an analytic function of the position, size, and texture of the object, empowering the designer to find the feeding fields for the lasers giving a perfect beam forming. In this way, an optimal beam-shaping equilibrium is re-established by effectively cloaking the object and nullifying its jamming effect.

Jamming game for secure orthogonal frequency division multiplexing access systems

In a communication system, security and reliability have an important impact on the quality of services. In this study, the authors investigate power and subcarrier allocation of a transmitter over the downlink of an orthogonal frequency division multiplexing access system with security considerations among users in the presence of a jammer. This study considers the interaction between the jammer and the transmitter as a zero-sum game where the objective function is the transmitter's secrecy sum-rate. To allocate the available resources, they solve the optimisation problem of each player to characterise its optimal strategies. Considering the intractability of the closed form Nash equilibrium for general power regime, they study a matrix game for obtaining maxmin and minmax solutions and demonstrate the validity of inequality m a x m i n ≥ m i n m a x . Moreover, they show the existence of pure Nash equilibrium point for low total power regimes of the transmitter and the jammer and attain an expression for each regime. Finally, they examine the jamming power effect on the secrecy sum-rate and acquire lower and upper bounds of this rate using simulations.

Outfield experiment of semiconductor laser jamming on color CCD camera

Outfield laser jamming experiment of color charge coupled device (CCD) irradiated by semiconductor laser was performed. The impact of incident power density I0 and the focus length f on laser jamming results was obtained. Laser jamming model of color CCD camera is set up, and theoretical proving and analysis on experimental results are completed. Laser jamming effects on color CCD camera irradiated by semiconductor laser is obvious, CCD surface appears obvious optical saturation and crosstalk phenomena, and optical saturation areas gradually enlarge with the increase of power density to target and the focus length f. Simulation results are basically coincident with experimental results, and it proves laser jamming model is correct. We argue that optical saturation phenomenon should be caused by laser diffraction effect, and the impact of the focus length f should be mainly due to laser energy truncated by the aperture. The conclusions have a reference value for color CCD in aerospace.

Hybrid Phased-MIMO Radar: A Novel Approach With Optimal Performance Under Electronic Countermeasures

This letter presents a novel technique for optimizing the performance of a phased-multi-in multi-out (MIMO) radar in the presence of strong jamming effects. The proposed technique not only overcomes the noise jamming but also counters the effects of deception jamming. Two orthogonal waveforms beam-formed by coherent operation of two sub-arrays are used to leverage the advantages of both the MIMO and phased-radar simultaneously. The heart of the idea lies with its coherent receive operation where matched filtering and Karhunen–Loeve transform is applied for separating the signals. We make use of the MUltiple SIgnal Classification (MUSIC) algorithm for angle estimation; thereafter the signal-to-noise-plus-jamming ratio is maximized by solving a convex optimization problem. The output shows remarkable results with an excellent peak to sidelobe ratio of more than 40 dB.

A Variable Stiffness Soft Gripper Using Granular Jamming and Biologically Inspired Pneumatic Muscles

As the domains, in which robots operate change the objects a robot may be required to grasp and manipulate, are likely to vary significantly and often. Furthermore there is increasing likelihood that in the future robots will work collaboratively alongside people. There has therefore been interest in the development of biologically inspired robot designs which take inspiration from nature. This paper presents the design and testing of a variable stiffness, three fingered soft gripper, which uses pneumatic muscles to actuate the fingers and granular jamming to vary their stiffness. This gripper is able to adjust its stiffness depending upon how fragile/deformable the object being grasped is. It is also lightweight and low inertia, making it better suited to operation near people. Each finger is formed from a cylindrical rubber bladder filled with a granular material. It is shown how decreasing the pressure inside the finger increases the jamming effect and raises finger stiffness. The paper shows experimentally how the finger stiffness can be increased from 21 N·m−1 to 71 N·m−1. The paper also describes the kinematics of the fingers and demonstrates how they can be position-controlled at a range of different stiffness values.

Iot based real time trafic control using cloud computing

The rapid increase in the number of vehicles has given rise to the traffic jam, which is a major problem these days. The effect of traffic jam also effects the operation of ambulance. To avoid the traffic jam for the ambulance, a new idea is developed. In this paper we propose a new concept to avoid traffic jam for the ambulance and thus saving the life of an individual. At first the ambulance is detected and the information about the arrival of the ambulance is sent to the next station. The ambulance will make siren only when it carries patient inside, so by detecting both the ambulance siren and the image taken from the acquisition device, the information is sent to the next point which is on the way to hospital. Announcement of the arrival of the ambulance is done. The CCTV camera is monitoring each vehicle on that road. If any vehicle doesn’t abide by the announcement done, the image of the vehicle will be captured, and then by using the acquired image the number plate will be tracked and will be detected automatically by image processing. The vehicle information is sent to the police station, to take the necessary action. Thus the traffic control can be done and the way is cleared for the ambulance and life is saved. The processing is done using MATLAB and is verified.

Robust Relay Beamforming Against Jamming Attack

In this letter, we surpass the jamming effect and also estimate the jamming channel state information by using the Kalman filtering approach. Furthermore, we design a closed-form beamforming weight for maximizing the achievable rate subject to the condition that the total relays power transmission would be below a predefined threshold level, which is formulated as a quadratically constrained quadratic program. Simulation results show the efficient performance of the proposed method for different destruction powers of the jammer by achieving the Cramer–Rao lower bound.

A Learning Method for Secondary Users to minimize the effect of Jamming in Cognitive Radio Wireless Sensor-Networks State of the art in CR-WSN security

A Learning Method for Secondary Users to minimize the effect of Jamming in Cognitive Radio Wireless Sensor-Networks State of the art in CR-WSN security

Comparing thixotropic and Herschel–Bulkley parameterizations for continuum models of avalanches and subaqueous debris flows

Abstract. Avalanches and subaqueous debris flows are two cases of a wide range of natural hazards that have been previously modeled with non-Newtonian fluid mechanics approximating the interplay of forces associated with gravity flows of granular and solid–liquid mixtures. The complex behaviors of such flows at unsteady flow initiation (i.e., destruction of structural jamming) and flow stalling (restructuralization) imply that the representative viscosity–stress relationships should include hysteresis: there is no reason to expect the timescale of microstructure destruction is the same as the timescale of restructuralization. The non-Newtonian Herschel–Bulkley relationship that has been previously used in such models implies complete reversibility of the stress–strain relationship and thus cannot correctly represent unsteady phases. In contrast, a thixotropic non-Newtonian model allows representation of initial structural jamming and aging effects that provide hysteresis in the stress–strain relationship. In this study, a thixotropic model and a Herschel–Bulkley model are compared to each other and to prior laboratory experiments that are representative of an avalanche and a subaqueous debris flow. A numerical solver using a multi-material level-set method is applied to track multiple interfaces simultaneously in the simulations. The numerical results are validated with analytical solutions and available experimental data using parameters selected based on the experimental setup and without post hoc calibration. The thixotropic (time-dependent) fluid model shows reasonable agreement with all the experimental data. For most of the experimental conditions, the Herschel–Bulkley (time-independent) model results were similar to the thixotropic model, a critical exception being conditions with a high yield stress where the Herschel–Bulkley model did not initiate flow. These results indicate that the thixotropic relationship is promising for modeling unsteady phases of debris flows and avalanches, but there is a need for better understanding of the correct material parameters and parameters for the initial structural jamming and characteristic time of aging, which requires more detailed experimental data than presently available.

导弹战术参数对面源红外诱饵干扰效能影响

Surface source infrared decoy is regarded as the new type weapon to confront infrared guided missile. In comparison with traditional infrared decoy, it has obvious superiority in burning rate, diffusion range, jamming effectiveness and so on. It's of great significance to study the anti-interference mechanism of infrared guided missile for improving the jamming effectiveness. Firstly, the models of missile motion, seeker tracking and the optimization algorithm of tracking were introduced. Secondly, the models of flight motion and radiation were established, as well as models of surface source infrared decoy diffusion and infrared image. Finally, the tactical parameters of missile was selected and the indicator of effectiveness evaluation was formulated, based on which, comparing the simulation results with testing data to verify the reasonability of simulation result. It's concluded from simulation that the simulation results of the influence of tactical parameters of missile on jamming effectiveness of surface source infrared decoy match the testing data, being of great reference value.

Multiple Targets Deception Jamming Against ISAR Based on Periodic 0- $\pi$ Phase Modulation

As many target characteristics can be extracted from the echoes by inverse synthetic aperture radar (ISAR), the jamming signal on ISAR need to simulate the electromagnetic scattering characteristics and kinematics characteristics with high fidelity. Based on the principle of periodic 0- $\pi $ phase modulation, a method generating 2-D ISAR group targets is proposed. Radar pulses are sampled and modulated according to periodic 0- $\pi $ phase sequence by the escort free-flight jammer, and then the modulated signals are retransmitted to the protected target, which can generate verisimilar false target images in ISAR. After the principle of escort free-flight jamming is introduced, the theory of periodic 0- $\pi $ phase sequence is expounded. The generation process of jamming signal is analyzed. According to the 2-D output expression, the jamming effects with different modulation parameters are demonstrated. A theoretical study is carried out to determine the number, amplitude and space distribution of false targets. Experimental results of scattering model of an aircraft illuminate the effectiveness and correctness of the proposed method.

Chirping and asymmetric jamming avoidance responses in the electric fish Distocyclus conirostris.

Electrosensory systems of weakly electric fish must accommodate competing demands of sensing the environment (electrolocation) and receiving social information (electrocommunication). The jamming avoidance response (JAR) is a behavioral strategy thought to reduce electrosensory interference from conspecific signals close in frequency. We used playback experiments to characterize electric organ discharge frequency (EODf), chirping behavior and the JAR of Distocyclus conirostris, a gregarious electric fish species. EODs of D. conirostris had low frequencies (∼80-200 Hz) that shifted in response to playback stimuli. Fish consistently lowered EODf in response to higher-frequency stimuli but inconsistently raised or lowered EODf in response to lower-frequency stimuli. This led to jamming avoidance or anti-jamming avoidance, respectively. We compare these behaviors with those of closely related electric fish (Eigenmannia and Sternopygus) and suggest that the JAR may have additional social functions and may not solely minimize the deleterious effects of jamming, as its name suggests.

Cross-Layer Anti-Jamming Scheme: A Hierarchical Learning Approach

This paper investigates the cross-layer optimization for anti-jamming in the network and MAC layers, in which the jammer can adjust the jamming policies to maximize the jamming effectiveness. The joint problem of routing selection, channel allocation, and power control is formulated as a Stackelberg game. The jammer leads the game by choosing the optimal jamming power and channels. The user follows by selecting the optimal nodes and corresponding channels, and adjusts its transmitting power to meet the communication requirement. Then, based on Q-learning, a cross-layer anti-jamming learning algorithm is proposed to obtain the Stackelberg equilibrium. Finally, simulation results are presented to verify the effectiveness of the proposed algorithm.

A Novel Passive Jamming Method Against ISAR Based on Resonance Absorption Effect of Metamaterials

Based on resonance absorption effect of metamaterials, a novel passive jamming method against Inverse Synthetic Aperture Radar (ISAR) is proposed in this paper. By adopting a cross-shaped metamaterial, the resonance frequency is designed within the ISAR bandwidth. Using the finite integration technique to calculate the electromagnetic reflection characteristics, the scattering point model and distorted radar echo of the target coated with the designed metamaterial are obtained. Then, the ISAR imaging analysis model of the target coated with the cross-shaped metamaterial is established. Finally, jamming effects of the cross-shaped metamaterial on the ISAR imaging are studied and verified. The range profile result indicates that besides the energy attenuation, the single radar target becomes two false radar targets, both of which are not located at the real target position. The ISAR imaging result shows that the target becomes blurred and many low-brightness points are produced. The passive jamming method could have a negative impact on the ISAR image target recognition applied to aircrafts, ships, and missiles.

Towards Secure and Energy-Efficient CRNs Via Embracing Interference: A Stochastic Geometry Approach

In a cognitive radio network (CRN), the interference caused by secondary users (SUs) is conventionally regarded as an obstacle to the throughput of the primary network. However, when considering security, the interference brings potential benefits to the secrecy throughput of the primary network. For a stand-alone primary network, the secrecy guard zone, including the cooperative mode and non-cooperative mode, has been shown as an efficient method to enhance the network security. The cooperative mode is traditionally thought to outperform the non-cooperative mode due to the jamming effect of the artificial noise generated by primary transmitters on eavesdroppers. However, allowing SUs to access the licensed spectrum, the resulting interference can be used as a source of the artificial noise instead of that generated on purpose by primary transmitters, which in return benefits the energy efficiency of the primary network. Inspired by the two benefits brought by SUs, this paper considers a random underlay CRN with eavesdroppers overhearing primary transmissions. To enhance both the security and energy efficiency of the primary network, we apply a secrecy guard zone around each primary transmitter, and adopt the non-cooperative mode. We exploit the stochastic geometry to model such a random CRN and analyze the connection/secrecy probability of primary links. We propose a criterion for guaranteeing the performance of secure primary network. The main idea is that compared with the primary network with the cooperative mode, the access of SUs should not reduce the secrecy throughput and energy efficiency of the primary network with the non-cooperative mode. Based on the obtained analytical results, we design the optimal secondary link scheduling schemes under the criterion. Both analytical and numerical results show that the interference from SUs can be exploited toward a secure and energy-efficient primary network and provide SUs with extra transmission opportunities.

面源红外诱饵干扰效能评估系统仿真研究

面源红外诱饵干扰效能评估系统仿真研究