Search

To protect our receivers against spoofing, intrusion or simply reduce interference, we proposed a multi-layered architecture which can be integrated into a receiver chain by modifying the analog and digital parts. Indeed, Our project addresses analog circuits coupled with digital approaches to immunize a radio against any intentional electromagnetic attack (intelligent jammer or not), or radio interference. In this manuscript, we only consider the innovative analog part of our system which is based on non-linear bijective functions generated by electronic circuits. In fact, we have developed an electronic system characterized by a non-linear bijective function that can be implemented using analog electronic components, and its inverse function can be implemented in the digital part of our reception chain. The main purpose of these two functions is the protection of an interesting weak signal existing in the vicinity to an annoying but very strong signal which will risk saturating the Low Noise Amplifier (LNA), and therefore the target signal can no more be chased after the analog to digital convertor (ADC). Certainly, in conventional transmission systems, we generally seek to eliminate or to reduce the impact of non-linear effects of certain electronic components or devices; however, our proposed scheme introduce a specific non-linear function in ordre to detect the presence of signals with weak Signal to Interference plus Noise Ratios (SINR). This manuscript presents our study and discusses various aspects related to the proposed new nonlinear scheme.

Fourth-generation (4G) mobile networks are successively replaced by fifth-generation (5G) ones, based on the new releases of the 3rd Generation Partnership Project (3GPP) standard. 5G generation is dedicated to civilian users and the conducted analytical work shows that it has numerous technological gaps that prevent its direct implementation in military communications systems. However, the recent armed world conflicts showed that closed or public mobile networks are willingly used by soldiers for both private and business communications, and to conduct defensive and offensive operations as well. From the military operation viewpoint, jamming both civil and military systems is one of the essential elements of electronic warfare. This paper focuses on the practical trial of low-energy and smart jamming on a 5G private network using narrowband signals, which facilitates the reduction of the available throughput, e.g. in the time division duplex - uplink (TDD-UL) by 99%, or by 82% in the frequency division duplex - downlink (FDD-DL). This type of jamming also allows for reaching up to 25 dB of energy gain comparing to barrage jamming. The authors moreover investigated jamming the Narrowband IoT radio interface using synchronized, selective jamming. The goal was to propose energy efficient methods that will allow the jammers to work longer and be mounted on a small unmanned aerial vehicle (UAV) that can operate near the gNB. The generation of low-power jamming signals in the gNB vicinity successfully hinders detecting the jammer by the enemy’s electronic reconnaissance systems. The proposed solutions are compared with the test results for other types of jamming methods.

Traditional deinterleaving algorithms first cluster the pulses in frequency, pulse width, and angle of arrival parameter space. Then, they utilize time of arrival analysis techniques. This results in a performance loss, since these processes are not jointly combined; rather, they are sequentially connected. Additionally, they perform poorly in the presence of radars with staggered pulse repetition interval type due to abrupt time difference variations. To alleviate the suboptimality in the design and enhance the detection performance in the staggered type, we propose a combined approach based on the pulse repetition interval transform technique. It does not cluster the pulses as the traditional methods, instead, it combines all pulses by distance weighting. It deals with the detection problem in the staggered type by clustering the phases of the autocorrelation function. We develop an optimal weighting mechanism to fuse the outputs from phase clusters. Numerical results show that our method outperforms the traditional methods in different detection metrics via multiple scenarios, which is also validated by the theoretical findings.

Deceptive jamming is one of the indispensable part of electronic countermeasure technology, which has a significant role in modern warfare to secure the aircrafts from imminent threats. This research work proposes a novel Frequency Diverse Array-Multiple Input Multiple Output (FDA-MIMO) deceptive jamming method for neutralizing the opponent Phased Array Radar (PAR). The proposed deceptive jamming model works in passive mode. It interrupts the opponent radar signals and after addition of the deceptive signals, the processed signals are propagated back to neutralize the surveillance operation of the intended radar. When the opponent PAR receives these signals, it perceives multiple fake aircrafts flying at different ranges along the actual aircraft with modified and up-shifted radial velocity. Further, the proposed model uses diversification in frequencies, waveforms, and time modulation to protect the flight of the preferred aircraft. The effectiveness of the proposed model is verified through several simulations in Matlab using different number of arrays, directions and ranges.

Estimating the time of arrival (TOA), pulse width (PW), and pulse repetition interval (PRI) is critical for identifying the low probability of intercept (LPI) radar signals as it is common in electronic warfare (EW) to experience a pulse train being received. To determine these parameters, we need to differentiate between pulse and noise in a pulse train. However, separating the LPI radar pulse train into pulse and noise is challenging owing to its characteristics and modulation scheme. Therefore, we propose a method to accurately estimate TOA, PW, and PRI using change point detection, which can effectively classify the pulse train into pulse and noise. The main contributions of this study are as follows. First, a denoising method robust to various modulation schemes is introduced. Second, an algorithm capable of estimating the parameters without considering the threshold calculation is presented. Moreover, most prior studies have entailed parameter estimations for a single pulse. In contrast, we focus on estimating parameters when a pulse train is intercepted and generating superior results even in the signal-to-noise ratio under 0 dB. We present experiments performed on the following eight modulation schemes: linear frequency modulation, Costas, Barker, Frank, P1, P2, P3, and P4 codes. Furthermore, we compare the proposed method with the wavelet-based method, which has received much attention in EW. The results demonstrate that the proposed method outperforms the conventional approaches.

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. [ABSTRACT FROM AUTHOR]

A disambiguation method for dual-comb sampling frequency measurement is proposed and experimentally demonstrated. For dual-comb sampling frequency measurement, multiple solutions may exist if only the frequency information of the output signal is employed for disambiguation. By further exploiting the phase relationship between the intermediate frequencies and the first harmonics of the two sampling rates, most of the ambiguous frequencies can be distinguished in our experiment. The experiment results also indicate that nonideal phase response of the devices will reduce the performance of the method especially in high frequencies. To solve the problem, an improved method, in which the variations of the phases are observed and used to solve the ambiguity, is given so that the method is free from the calibration of the nonideal phase response. [ABSTRACT FROM AUTHOR]

An experimental approach to estimate cross-eye gain for a nonretrodirective cross-eye jamming (NRCJ) system is presented. Cross-eye gain is used as an index to evaluate the cross-eye jamming system. The previous experimental method for obtaining the cross-eye gain using a network analyzer is accurate but requires a complex configuration. In this letter, a method of estimating the cross-eye gain for the NRCJ system by the signal power difference using a spectrum analyzer is proposed. To verify the proposed method, a prototype of the NRCJ system was fabricated. The experimental results showed that the proposed method could estimate the cross-eye gain with a phase-difference error of approximately 2° compared to the simulation. [ABSTRACT FROM AUTHOR]

In the modern electronic warfare signal environment, multiple radar signals of high density are mixed and received, and separating them into signals for each emitter is an essential step for emitter identification. Each radar has its own pulse repetition interval (PRI), which is a key parameter for deinterleaving pulse trains. The PRI is modulated in various forms depending on the purpose of the radar operation, and analyzing the mean PRI and the modulation type of PRI is the core of electronic warfare signal processing. Many existing papers have tried separate independent approaches for deinterleaving and for PRI modulation recognition. However, many distortions are unintentionally generated in the process of extracting the pulse train using the PRI estimated through deinterleaving for the PRI modulation recognition. This degrades the modulation recognition performance. In this paper, we propose a unified method for the deinterleaving and PRI modulation recognition of radar pulses using deep learning-based multitasking learning. The simulation results demonstrate the good performance of the proposed method for deinterleaving and modulation recognition, compared to the conventional method, and prove that the proposed method is robust in noisy radar signal environments.

In this article, a machine learning aided electronic warfare (EW) system is presented and the simulation results are discussed. The developed EW system uses an automatic decision tree generator to create engagement protocol and a fuzzy logic model to quantify threat levels. A long-short term memory (LSTM) neural network was also trained to predict the next signal set of multifunction radars. The simulation results demonstrate the effectiveness of the developed EW system’s ability to engage multiple multifunction radars.

Radar signal sorting (RSS) plays an important role in the electronic support measurement system. However, the existing clustering-based RSS methods depend heavily on prior knowledge to achieve excellent performance, which may bring severe challenges to RSS in actual scenarios. This letter proposes a novel subspace decomposition based adaptive density peak clustering (SD-ADPC) method to address the problems of low accuracy and high computational cost in RSS. First, the original complex radar signal data is directly decomposed into two-dimensional (2D) subspace by t-distributed random neighborhood embedding (t-SNE). Then, based on the outlier detection of the products between the peak density and the distance of the data points, ADPC is used to adaptively determine the optimal clustering centers of the original data in 2D subspace. Finally, the reminding data is assigned to its nearest cluster with Euclidean distance in one step. The experimental results of the simulated RSS dataset and the open baselines show that our proposed method does not require any knowledge and can achieve better or competitive performance in terms of accuracy and computational cost, compared to existing state-of-the-art methods. [ABSTRACT FROM AUTHOR]

Hybrid modulation continuous waveform (HMCW) proximity detectors emit binary phase-coded chirp (BPCC) waveforms. Therefore, they possess the advantages of binary phase-coded modulation and chirp modulation simultaneously. To enhance the anti-sweep-jamming performance of HMCW detectors, this paper analyses the response of an HMCW detector under sweep jamming and proposes an anti-jamming method based on the novel average range side lobe (ARS) approach. Similar to the instant correlation with harmonic demodulation (ICHD) method, the ARS method also combines time-domain instantaneous correlation with frequency-domain harmonic demodulation to obtain the range information of the target. The difference is that the ARS method uses a fast Fourier transform (FFT) instead of a band pass filter (BPF) to extract the harmonic envelope and averages multiple harmonic coefficients obtained via the FFT. Because the correlation side lobes of chaotic codes follow a Gaussian distribution, the output of an HMCW detector under sweep jamming is suppressed after ARS processing. The proposed method is proven to be feasible and effective through numerical simulations. The results show that the ARS method offers improved anti-sweep-jamming performance.

Analyzing radar signals is a critical task in modern Electronic Warfare (EW) environments. However, the pulse streams emitted by radars have flexible features and complex patterns which are difficult to be identified from a statistical perspective. To solve this problem, pulse repetition interval (PRI) is used as a distinguishing parameter of emitters to be identified. However, traditional PRI modulation recognition methods can only deal with simple PRI modulations and their performance will further degrade with the increasing number of emitters or noisy environments. In this paper, we introduce an attention-based recognition framework based on recurrent neural network (RNN) to categorize pulse streams with complex PRI modulations and in environments with high ratios of missing and spurious pulses. Simulation results show that our model is robust to noisy environments and has a better performance than conventional methods.

Electronic warfare (EW) is one of the most important characteristics of modern battles. EW can affect a military force's use of the electromagnetic spectrum to detect targets or to provide information. Recent developments in artificial intelligence (AI) suggest that this emerging technology will have a deterministic and potentially transformative influence on military power. AI driven algorithms can be very effective in diverse domain of EW like processing of radar signals for efficient recognition and classification of emitters, detection of jammer and its characteristics and for developing efficient anti-jamming algorithms. AI techniques can also enable an EW system to operate autonomously. This paper provides a description of various branches of EW, the role of AI in EW systems and different AI techniques that have been deployed in EW systems.

Radar radio source (RRS) recognition plays an important role in the fields of military electronic support systems (ESM) and civilian autonomous driving. The rapid development of machine learning technology, especially deep learning, has effectively and efficiently improved RRS intelligent recognition performances when operating in the increasingly complex electromagnetic environment. However, the data sampling limitation and computation cost are still severe challenges in real RRS recognition scenarios. In this paper, we propose a novel network based on meta-transfer learning, called RRSARNet, to achieve effective adaptive RRS recognition in the context of low signal-to-noise ratio (SNR). First, by using the short-time Fourier transform, a six-type small samples RRS simulation dataset with different SNR levels is constructed. Then, a novel RRSARNet, based on metric learning, is proposed, which consists of a four-layer embedding module and a four-layer relational module. Finally, the RRS dataset is divided into training, supporting and testing subsets, which are used to train and test the RRSARNet in a meta-transfer learning method. Experiments on the RRS dataset show that the proposed RRSARNet can achieve an overall accuracy (OA) above 96% and 99% when the SNR is above −15 dB and −10 dB, respectively. Even when the SNR is -30 dB, OA can reach more than 70%. For 5-way 1-shot and 5-way 5-shot experiments, the inference time of an image is about 0.043 and 0.140 milliseconds, respectively. Besides, experiments on the RRS simulation dataset and the two benchmark datasets, the RRSARNet performs better or more competitive than many existing state-of-the-art technologies in terms of recognition accuracy. [ABSTRACT FROM AUTHOR]

In this paper, we focus on the localization of a passive source from time difference of arrival (TDOA) measurements. TDOA values are computed with respect to pairs of fixed sensors that are required to be accurately time-synchronized. This constitutes a weakness as all synchronization techniques are vulnerable to delay injections. Attackers are able either to spoof the signal or to inject asymmetric delays in the communication channel. By nature, TDOA measurements are highly sensitive to time-synchronization offsets between sensors. We first illustrate that time-synchronization attacks can severely affect the localization process. With a delay of a few microseconds injected on one sensor, the resulting estimate might be several kilometers away from the true location of the unknown source. We show that residual analysis does not enable the detection and identification of time-synchronization attacks. Our main contribution is then to propose a two-step TDOA-localization technique that is robust against time-synchronization attacks. It uses a known source to define a weight for each pair of sensors, reflecting the confidence in their time synchronization. Our solution then uses the weighted least-squares estimator with the newly created weights and the TDOA measurements received from the unknown source. As a result, our method either identifies the network as being too corrupt to localize, or gives a corrected estimate of the unknown position along with a confidence metric. Numerical results illustrate the performance of our technique. [ABSTRACT FROM AUTHOR]

Electronic Warfare (EW) scenarios contemplate powerful and stealthy jamming attacks, able to disrupt any competing wireless communication in the target area. Reactive jamming techniques are especially suitable to this aim. Indeed, by first eavesdropping on the whole radio spectrum used for communications, and then timely injecting random noise as soon as a transmission is detected, reactive jamming represents both an effective and hard-to-detect attack tool. In such a challenging EW scenario, all the solutions currently available in the literature to mitigate reactive jamming require either the deployment of specialized hardware, or the modifications of physical layer protocols-the former solution being expensive, and the latter one usually not viable when considering commercially available wireless devices. In this paper we propose BitTransfer, an anti-jamming protocol enabling wireless communications between neighboring devices even under the above-described stringent requirements and powerful attacker model. BitTransfer embeds information bits in radio activity operations, a 0 being represented by the absence of any radio activity, and a 1 by the reception of a (corrupted) packet at the receiver. To demonstrate its applicability to a wide class of commercial wireless devices, BitTransfer has been implemented using a real constrained hardware platform (the Openmote-b), released as freely available and open-source, and tested using the IEEE 802.15.4 communication technology, adopted within the Bluetooth and Zigbee 3.0 protocol stacks. When under attack by a reactive jammer, BitTransfer can transfer a message of 127 Bit in 11.17 seconds, while competing approaches simply fail. Other than being completely tunable, BitTransfer can also enjoy further improvements by simply increasing the transmission rate of the devices. Finally, its detailed design, open-source availability, robustness, and superior performance when compared against competing solutions, make it a solution of choice in challenging EW scenarios, also paving the way to further research along the highlighted directions.

The authors present transmit-adaptive jammer nulling waveforms in cognitive radar (CRr) for aircraft response recognition as a form of electronic support in the electronic warfare domain. New forms of knowledge-based noise jammers that function as a form of electronic attack to matched illumination waveforms are also introduced. These knowledge-based noise jamming techniques capitalize on prior knowledge of the target's frequency response to obscure the true target response echo. The results from simulation show that real-time adaptive waveforms suppress the effects of electronic attack noise jammers and the newly introduced knowledge-based noise jammers. High bandwidth radar cross section (RCS) responses via electromagnetic (EM) simulations of true-to-physical-size aircraft are used for simulations to produce CRr classification performance against a comprehensive list of noise jammers.

In this article, the power capabilities of the axially extracted virtual cathode oscillator are determined by analytical means. The used methodology comprises two stages. First, power limits are established by mathematical optimization of a Vircator power model calculating the average power radiated at a given frequency. Second, the analytical results are validated by comparison against computational simulations. The presented analysis is in agreement with the reported experimental data and computational simulation. [ABSTRACT FROM AUTHOR]

A concurrently dual-polarized, simultaneous transmit and receive (STAR) antenna system with high transmit (TX)-receive (RX) isolation is presented. The STAR antenna consists of four dual-polarized patches, two for TX and two for RX. The radiators are fed using a network consisting of four 90° hybrids and four 180° hybrids. The input ports of the feed network constitute the inputs/outputs of the STAR antenna system. The system supports concurrent transmission and reception of waves with both right- and left-hand circular polarization. Due to the phase cancellation and geometrical symmetry of the antenna, the TX/RX coupling between ports with the same polarization is canceled using the feed network. In addition, four right-angle slots are inserted in the ground plane and a cross-shaped, high-impedance surface is inserted between the radiating patches to further suppress the coupling between the differently polarized TX and RX ports. Simulation and measurement results of a fabricated prototype show good agreement and demonstrate TX/RX isolation levels greater than 38 dB for all polarization combinations over a 6.5% bandwidth (6.0–6.4 GHz). Moreover, the fabricated prototype provides broadside axial ratios below 2.5 dB and realized gains above 7.8 dBic for all TX and RX modes, demonstrating good, concurrent-dual-polarization performance. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Electronic warfare receivers must satisfy particularly demanding requirements, and current electronic solutions must find a tradeoff between the request for high performance (in particular, very wide bandwidth, very high sensitivity, and very linear response) and the need for light and small systems. Photonics has been often proposed as a potential enabler of performance improvements, thanks to its wide tunability and precision, and recently the advancements of the photonic integration technologies are also promising strong reductions of size and weight. In this paper, we present an overview of the photonics-based solutions proposed so far in the field of electronic warfare. In particular, we focus on the specific implementation of a spectrum scanner we have recently proposed. Besides the performance in terms of bandwidth, linearity, and sensitivity, which are on par with the state-of-the-art electronic commercial systems, here, we report on our last advancements in terms of tuning speed. Further improvements are also discussed, in terms of both tuning speed and integrability. [ABSTRACT FROM AUTHOR]

Multiloop retrodirective cross-eye jammers offer the possibility of both simplifying system implementation and improving system performance. However, the signals for each jammer loop propagate along different paths, leading to potentially detrimental effects on system performance. Static and dynamic compensation for path-length differences are introduced and analyzed. Of the two, static compensation is simpler but is only effective for limited engagement geometries. Dynamic compensation is more general but requires an accurate estimate of the engagement geometry. [ABSTRACT FROM AUTHOR]

The use of channel code is mandatory in current digital communication systems. It allows us to access the information on the receiver side despite the presence of noise. In this paper, we are interested in the blind identification of the parameters of an error correcting code from a received noisy data stream. The literature provides a large amount of contributions for this problem in the hard-decision case but few in the soft-decision case. It is well known that soft-decision methods allow significant gain in decoding techniques. Thence, we propose an algorithm which is able to identify the length of a code through a classification process from the bits likelihood values. It highlights a difference of behavior between an independent identically distributed sequence and an encoded one. This method does not rely on any a priori knowledge about the encoder involved. Indeed, the distribution of $n$ -length code words in an $n$ -dimensional space depends on the encoder characteristics. Some areas of this $n$ -dimensional space are left vacant because of the redundancy added by the encoder. Despite the presence of noise, it is still possible to detect this phenomenon. Furthermore, an adaptation of a collisions method based on the birthday paradox gives us access to an estimation of the code dimension. Finally, we investigate the performance of this estimation methods to show their efficiency. [ABSTRACT FROM AUTHOR]

A wideband planar unidirectional circularly polarized (CP) antenna with simultaneous transmit and receive (STAR) capability is presented for full-duplex applications. The proposed STAR antenna consists of four radiating elements and is fed with a custom-designed feed network. The radiating elements are identical CP patch antennas, which are sequentially rotated along the center of the STAR antenna. The four radiating elements are symmetrically distributed along the perimeter of a circle. The feed network is composed of two identical 180° power dividers. Each pair of CP elements, placed opposite to each other on one of the axes of symmetry of the STAR antenna, is excited together using one of the 180° power dividers. This way, a null is created along the other axis of symmetry of the STAR antenna causing near-field cancellation at the location of the other two antennas. A prototype of the proposed STAR antenna operating in the 6.0–7.2 GHz frequency range is designed, fabricated, and experimentally characterized. Measurement results show that the antenna provides an isolation better than 40 dB, an axial ratio better than 3 dB, and a gain higher than 8.7 dBic over this entire band of operation. [ABSTRACT FROM PUBLISHER]

This paper introduces the concept of antifragile communications, which we define as the capability for a communications system to improve in performance due to a system stressor or harsh condition. Antifragility refers to systems that increase in capability, resilience, or robustness as a result of mistakes, faults, attacks, or failures. An antifragile system is fundamentally different from one that is resilient (able to recover from failure) and robust (able to resist failure). We apply the concept of antifragility to wireless communications where the system stressor is a jammer that intends to disrupt the underlying communications. Through a novel strategy, we exploit the communications jammer, providing an increase in communications capability such as bits per second. We show that an antifragile gain is possible under a wide variety of reactive jamming scenarios and provide guidelines for realizing these gains by creating an antifragile waveform. [ABSTRACT FROM PUBLISHER]

A high-isolation, ultra-wideband simultaneous transmit and receive (STAR) antenna with monopole-like radiation characteristics is presented. The proposed STAR antenna consists of a center-located monocone and a circular array of bent loops. The monocone and the array of loops are located in the near fields of each other and serve, respectively, as the transmit (TX) and receive (RX) antennas. To achieve omnidirectional, vertically polarized radiation patterns, the array factor of the bent loops is first examined. A circular top loading and four T-shaped parasitic elements are exploited to decrease the lowest frequency of operation of the antenna without increasing its occupied volume. Finally, based upon the analysis of the array factor, four directors are strategically mounted over the ground plane to enhance the omnidirectionality of the antenna in the azimuth plane. A prototype of the antenna operating in the UHF band is fabricated and measured. Experimental results demonstrate that the proposed STAR antenna achieves an isolation greater than 40 dB from 0.6 to 1.75 GHz (2.9:1 bandwidth). Furthermore, the STAR antenna is capable of maintaining consistent monopole-like radiation patterns and vertical polarization for both the TX and the RX channels across the entire band of operation. [ABSTRACT FROM PUBLISHER]

In this paper we focus on deriving an approximate Cramer–Rao lower bound (CRLB) for the parameters of a multicomponent linear frequency modulated continuous wave (LFMCW) signal corrupted by complex additive white Gaussian noise. The approximation is necessary due to the discontinuities inherent in the mathematical model of the instantaneous phase of each LFMCW signal model. By comparing our approximate bound to a simulation of the maximum likelihood estimator (MLE) of the LFMCW parameters, we confirm our analysis. In general, the CRLB is a useful tool for feasibility studies or in evaluating the degree of suboptimality that non-MLE methods exhibit. For passive detection and estimation of LFMCW signals, the Generalized Likelihood Ratio Test and the associated MLE are difficult to implement in practice, primarily due to their large computational requirements. So, lower bounds on performance, such as those provided by the CRLB, are necessary to evaluate suboptimal methods that are more suited for practical implementations. [ABSTRACT FROM PUBLISHER]

In this paper, improved signal processing techniques are developed for the analysis and classification of low probability of intercept (LPI) radar waveforms. The intercepted LPI radar signals are classified based on the type of pulse compression waveform. They are classified as linear frequency modulation, nonlinear linear frequency modulation, binary frequency shift keying, polyphase Barker, polyphase P1, P2, P3, P4, and Frank codes. The classification approach is based on the parameters measured from the preprocessed radar signal intercepted by electronic support (ES) or electronic intelligence (ELINT) system. First, signal embedded within the noise is estimated using Wigner Ville distribution to improve the signal-to-noise ratio (SNR). Next, features are extracted using the time-domain and frequency-domain techniques. Furthermore, parameters measured from the fractional Fourier transform are used for the classification. This type of techniques are required in various systems such as ES, electronic attack, radar emitter identification and multi input multi output (MIMO) radar applications. Extensive simulations are carried out with different LPI radar-modulated waveforms corrupted with additive white Gaussian noise of SNR up to –15 dB and impulse noise with 90% of noise density. The proposed algorithm outperforms the existing techniques of classification and can be used under strategic environment. [ABSTRACT FROM PUBLISHER]

Many modern radar systems are overcoming the need for high-power transmitters by utilizing low peak-power, high duty-cycle waveforms, making noncooperative detection methods by traditional electronic surveillance a difficult task. This technological difficulty is driving a need for computationally tractable detection and characterization algorithms. Here, a practical method for detecting and fully characterizing an arbitrary number of low-power linear frequency modulated continuous wave (LFMCW) radar signals is achieved by dividing the time-domain signal into contiguous segments and treating each signal segment as a sum of harmonic components corrupted by noise with an unknown, time-varying power spectral density. This method is developed analytically and evaluated experimentally, revealing that the practicality of the method comes at the ex-pense of a loss in estimation accuracy when compared to the Cramer–Rao lower bound. Experimental results indicate that the parameters of two simultaneous LFMCW signals can be estimated to within $10\%$ of their true values with probability greater than $90\%$ when input signal-to-noise ratios are $-$ 10 dB and above with a 25 MHz bandwidth receiver. [ABSTRACT FROM PUBLISHER]

This letter proposes a novel toroidal plasma lens with circular polarization, as an alternative solution for electronic warfare antennas. The aim of the proposed solution is to reduce the antenna profile and the radar cross section, thus minimizing the probability of target detection. The results compare the performance of the proposed antenna to a conical horn and to a spherical/elliptical lens. The toroidal plasma lens achieved equivalent gain, with reduced antenna profile and reduced near-field backscattering from the plasma toroid, thus maximizing the true power delivered to the far-field region. [ABSTRACT FROM PUBLISHER]

The complexity and sophistication of communications jamming will continue to increase over time. The traditional approach to jammer mitigation is to harden radios, often sacrificing communications performance for more advanced jamming protection. To provide an escape from this trend, we propose a jammer exploitation strategy in which the communications system causes an enemy reactive jammer to act as an unwitting relay. This can lead to an improvement in communications as a result of the jamming attack itself. The strategy proposed in this letter revolves around using a frequency-shift keying waveform that is tuned in such a way to exploit the jammer’s behavior. We derive the channel capacity when using the waveform along with practical coding, and provide numerical results to gain insight. [ABSTRACT FROM PUBLISHER]

Cross-eye jammers are required to operate in their near-field regions, so path-length differences between the jammers comprising a multiloop retrodirective cross-eye jammer cannot be ignored. The effects of these path-length differences are investigated and are shown to be significant in realistic cross-eye jamming scenarios. Notably, path-length differences have the potential to cause a multiloop retrodirective cross-eye jammer to act as a beacon rather than a jammer when the path-length difference is approximately 180 °. [ABSTRACT FROM PUBLISHER]

With the now widespread availability of software-defined radio technology for wireless networks, the distinction between jamming in the original electronic warfare sense and wireless cybersecurity attacks becomes hazy. A taxonomy delineates these concepts in the rapidly expanding field of wireless security, classifying communication jammers' theoretical behaviors and characteristics. [ABSTRACT FROM PUBLISHER]

Numerous papers dealing with the analysis of electromagnetic attacks against critical electronic devices have been made publicly available. In this paper, we exploit the principle of front-door coupling on smartphones headphone cables with specific electromagnetic waveforms. We present a smart use of intentional electromagnetic interference, resulting in finer impacts on an information system than a classical denial of service effect. As an outcome, we introduce a new silent remote voice command injection technique on modern smartphones. [ABSTRACT FROM AUTHOR]