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Main‐lobe blanket jamming is a challenging jamming pattern in electronic warfare. Based on the difference in spatial correlation between target echoes and jamming signals, signal cancellation has been used to suppress the main‐lobe jamming in multistatic radar. However, the cancellation residue and the extra superimposed noise would lead to serious degradation in target detection. In this paper, instead of cancelling the jamming in the power domain, a feature domain, named signal ratio feature domain, is defined to suppress main‐lobe jamming with the excepted targets retained simultaneously. The jamming signal is suppressed in the background due to the high correlation among different receivers, whereas the targets will be highlighted on account of its independence. Then, in the defined feature domain, a target detector with constant false alarm ratio in the Neyman–Pearson sense is applied to detect the highlighted targets. Numerical simulation is given to verify the jamming suppression ability of the proposed method, and the performance improvement in target detection compared with the available cancellation methods is also covered. [ABSTRACT FROM AUTHOR]

Here, the authors propose a novel robust adaptive beamforming method, which is robust to both of the covariance matrix mismatch and the steering vector estimation mismatch. Their method was based on a recently proposed adaptive beamforming technique for large-scale arrays. In this beamforming technique, a sparse sub-array having much smaller number of antenna elements is first selected from the original physical array to perform digital sampling, and then the beamforming coefficients for the original full array are calculated by using only the digital samples from the selected sub-array. In their robust method, they calculate the diagonal loading level automatically by using the spatial-matched method. Then, the steering vector of the desired signal is estimated by maximising the beamformer output power under a constraint that the estimated steering vector does not converge to any of the interference steering vectorsor their linear combinations. Numerical examples are provided to demonstrate the effectiveness of the proposed method against covariance matrix mismatch and steering vector error. [ABSTRACT FROM AUTHOR]

Strong adaptive radar, such as cognitive radar (CNR), can perform various missions while ensuring its own security in electronic warfare, via detecting environments and changing the radar parameters in real time. Unfortunately, most of the current military countermeasures, such as jamming-based electronic countermeasures, have rarely been related to jamming for CNR. Since the behaviours of radar in the traditional design of the jammer-radar scenario are always static, it is easy to create a subjective or local optimal jamming effect. In order to dynamically analyse the execution process of a complete jamming radar mission, this work establishes an equivalent attack-defence game in which the radar is regarded as a defence decision agent, and the jammer is an attack decision agent. The attributes of the game's players, the rules of the game, and the conditions for the end of the game are set clearly by setting reasonable parameters. After searching for antagonism strategies by exhaustive method, it can be found that the survivability of the predictive cognitive jamming is much stronger than that of the normal jamming based on real-time sampling data of radars. This conclusion is demonstrated through a 1 ms simulation of the game process. [ABSTRACT FROM AUTHOR]

In this study, a 2D adaptive beamforming algorithm for sparse array is proposed. Firstly, a signal model based on matrix completion theory for adaptive beamforming in sparse array is established, which is proved to satisfy null space property. Secondly, in order to enhance the performance of reconstructing complete received signal matrix, genetic algorithm is used to optimise the sparse sampling array. Thirdly, the accelerated proximal gradient algorithm is adopted to reconstruct the complete received signal matrix. Finally, the adaptive beamforming weight is provided directly to form beam patterns, which can be obtained as a result of reconstructing complete received signal matrix. The proposed method could improve the utilisation rate of the sparse array elements and reduce the computational complexity in interference suppression. Simulation results show the effectiveness of the method. [ABSTRACT FROM AUTHOR]

This study considers the problem of deceptive multiple false targets jamming recognition. Due to the different modulation patterns, there is a great difference in fast-time frequency spectrum or slow-time Doppler spectrum between the different types of jammings. The proposed algorithm first extracts the received sample matrix, then computes left and right similarity (LR-similarity) by fast-time-slicing or slow-time-slicing process and finally recognises the samples according to template matching classifier. Experimental results demonstrate that the accuracy recognition probability of the proposed method is >95%, when jamming-to-signal ratio is above 3 dB. [ABSTRACT FROM AUTHOR]

An algorithm is proposed to cancel the spatially non-stationary high-frequency (HF) interference in the returns of sky-wave over-the-horizon radar (OTHR). The algorithm could suppress the interference in side-lobe effectively based on spatial adaptive processing. Meanwhile, the algorithm preserves the temporal coherence of the clutter echoes using the zeroth Doppler channel output, of which the clutter-to-interference-plus-noise ratio is improved, to constraint the weight vectors. The performance results demonstrate the superiority of this algorithm. [ABSTRACT FROM AUTHOR]

High-frequency radar is easily affected by radio frequency interference (RFI) since it shares the band with many radio services. To mitigate the RFIs, this study designs receiver for radar's fast-time processing. Two optimisation problems are, respectively, proposed, both involving an objective function accounting for maximising the signal-to-interference plus noise ratio, but are distinguished with different constrains for sidelobes control. Furthermore, the authors show that the two proposed problems both can be reformulated as the second-order cone programming, hence some well-established interior point methods can be introduced to resolve them. Simulation results show that the designed filters can precisely control the sidelobe level from different perspectives, with the RFIs suppressed to achievable greatest extent. [ABSTRACT FROM AUTHOR]

This study proposes a direction-of-arrival (DOA) estimation algorithm named robust sparse asymptotic minimum variance (RSAMV) to solve the current DOA algorithms' problems, such as the difficulty in weak target estimation, low resolution and the incapacity of separating coherent signal estimation. Through utilising a virtual weak target, the algorithm carries out dynamic diagonal loading to the sampling covariance matrix of SAMV in the iterative process, which effectively reduces weak target loss. Meanwhile, showing the feature of ultra-low side lobe and high sparseness, the spatial spectrum of RSAMV can easily achieve the high-resolution estimation of space target in the circumstances of coherent interference. Simulation results show that, compared with other algorithms, the RSAMV algorithm has higher spatial resolution ability and weak target detection ability. Its spatial spectrum has higher sparseness than other sparse algorithms and its performance is more robust than other SAMV algorithms. The Bering-Time Recording map processed by results that experiment on sea demonstrate the superiority of RSAMV algorithm. [ABSTRACT FROM AUTHOR]

This study proposes a multi-ary modulation chirp spread spectrum algorithm specific for the unmanned aerial vehicles field. It further introduces the corresponding fractional Fourier transform de-spreading algorithm and the hardware implementation of the software radio-based communication system to validate the algorithm's better anti-interference performance in the wide-band non-stationary interference environment. [ABSTRACT FROM AUTHOR]

The synthetic aperture radar (SAR) may be threatened greatly by the deceptive jamming within its main-lobe. To tackle this problem, a two-dimensional self-adaptive frequency diverse array (FDA)-based SAR processing scheme is proposed in this study. Considering that transmit and receive steering vectors of FDA are range-angle dependent, in FDA-SAR, the spectrum distributions of true targets and jamming in joint transmit-receive frequency domain depends on the actual locations of scattering points and the jammer, respectively. Therefore, the false signal can be distinguished due to the mismatch in either range or angle. Then by employing a two-dimensional self-adaptive filter, the phony targets can be mitigated even if the jammer locates in the main beam. In the end, the simulation results showed that it achieves enhanced suppression capability and smaller ineffective area comparing with the static spatial filter in conventional multichannel SAR. [ABSTRACT FROM AUTHOR]

Polarisation is an inner property of electromagnetic wave. It has considerable significance to analyse the polarimetric feature of targets in target recognition and classification applications. Slant 45° dual polarisation measurement is widely used due to its low requirements on system complexity and data rate on the one hand, and good polarisation measure and anti-interference capabilities on the other. However, its performance is seriously affected by rotation angle of the polarisations in transmission and reception. Here, the impact of rotation error of the transmit–receive polarisations on feature extraction is assessed by theoretical derivation at first. The variations with rotation angles of the transmit–receive polarisations are then simulated using standard scatterers and ground targets data. This permits quantification of the resulting rotation error on slant 45° dual polarisation measurement. The impact of the rotation error on H/α and polarimetric similarity features is also quantified in results. Some practical advices on system design, calibration, and feature application are given at last. [ABSTRACT FROM AUTHOR]

Comprehensive assessment of guidance radar seeker anti-interference performance has important application value in complex electromagnetic simulation environment. Radar seeker performance evaluation is a systematic work including complex electromagnetic environment simulation, test data acquisition, and evaluation algorithm application. Evaluators need to judge how the seeker performance is based on data obtained by multiple tests. This study mainly discusses the application of analytic hierarchy process and Dempster–Shafer (D-S) evidential theory, which is based on posteriori probability in the radar seeker anti-interference performance assessment. Then, the authors give the algorithm application processes and assessment results combined with experimental data. Experiment results verify that both algorithms achieve similar assessment results, which support the reasonableness of two algorithms mutually. [ABSTRACT FROM AUTHOR]

The constant false alarm rate (CFAR) technology plays an important role in radar target detection. In cell averaging CFAR detectors, a reference window is usually adopted to estimate the average interference power in the range–Doppler matrix and to obtain the detection threshold, which should be set high enough to limit false alarm rate to a tolerably small rate. The conventional rectangular window, cross window, and column window are investigated in this study, which may suffer from a degraded detection performance due to involving some extraneous reference cells. Therefore, a modified reference window for two-dimensional CFAR is proposed to improve performance, depending on the distribution characteristics of radar targets in range and Doppler dimensions. The experimental results demonstrate its performance advantages on detection probability, CFAR loss, and figure of merit. [ABSTRACT FROM AUTHOR]

The relationship of different optimal waveform design criteria in signal-dependent interference, as well as additive channel noise for stochastic extended target, is investigated here. Within constraints on waveform energy and bandwidth, the optimal waveform design based on the signal-to-interference plus noise ratio criterion, probability of detection criterion, and mutual information criterion are modelled. Afterwards, the relationship of these criteria is presented. Simulations are conducted to illustrate that under the same bandwidth and energy constraints, the three criteria lead to the similar optimal waveform. The energy of optimal waveform can be distributed in some narrow bands where target power is large and interference power is small. [ABSTRACT FROM AUTHOR]

In random frequency-hopping pulse–Doppler radar, the transmitted frequencies are randomly distributed in the given frequency bandwidth. As a result, this kind of radar has the advantage of anti-jamming. However, because of the sidelobe level fluctuating randomly, the sidelobe of a large scatterer can mask the presence of nearby smaller scatterers. The adaptive pulse compression (APC) algorithm has been shown capable of effectively suppressing the range sidelobes, but the performance gain is diminished whenever the return signals have a low signal-to-noise ratio (SNR). Furthermore, moving targets with high speed bring about the range migration problem. To solve these problems, the coherent integration APC (CIAPC) algorithm is proposed. The simulation results indicate that in a low SNR scenario, the CIAPC algorithm can suppress the range sidelobes of large scatterers and can improve detection performance. [ABSTRACT FROM AUTHOR]

In order to realise effective target detection with a large baseline radar network interfered by a single radiation source, an adaptive processing method derived from traditional principal component analysis (PCA) and array signal processing theory is proposed in this study. First, the signal model for target detection with a large baseline radar system in an interference environment is established. Second, based on the characteristics of the signal model, an adaptive suppression method composed of high-precision delay alignment and modified PCA is proposed. Finally, the effectiveness of the method in a typical environment is verified by simulation. The results show that this method can accumulate target energy effectively and realise reliable detection in such case, which has great application prospects. [ABSTRACT FROM AUTHOR]

A hybrid CS-DL method for aircraft classification in complex electromagnetic environment is introduced. To classify aircraft from interfered radar echoes, the authors propose a novel classification method based on compressed sensing (CS) and deep-learning (DL). After recovering the spectrum polluted by jamming signals by using CS, they exploit sparse auto-encoder (SAE) to extract modulation features and then classify aircraft. The method is tested by 536 flights of three types of airplanes, and the results show that the correct classification rate reaches 75% even when 41% of the pulses are interfered. [ABSTRACT FROM AUTHOR]

With the development of modern electronic warfare, the jammer is becoming smarter than before and can be able to take actions according to the intercepted radar waveform. It has considerable significance for the radar to design a proper waveform to improve its performance when facing the smart jammer. Here, a novel cognitive radar waveform design method is proposed to improve the radar's performance. The relationship between the radar and the jammer is modelled as a two-person zero-sum Stackelberg game, where the cognitive radar is the leader and the jammer is the follower. Signal-to-interference and noise ratio (SINR) criterion is utilised as the utility function, where the radar tries to maximise the SINR while the jammer aims to minimise it. Lagrange multiplier method and particle swarm optimisation (PSO) algorithm is applied to solve the problem and the Stackelberg equilibrium (SE) is obtained. Numerical results show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The most common type of mixed jamming is composed of blanket jamming and deception jamming. In order to effectively detect the target signal in this kind of mixed jamming, this study presents an algorithm based on side-lobe cancellation (SLC) and slope-varying linear frequency modulation signal. The entire anti-jamming process is divided into two steps. SLC is used to suppress blanket jamming first, and then matched filtering is used to suppress deception jamming. The combination of these two algorithms can effectively suppress mixed jamming and accurately detect the target. The simulation analysis shows that this method can effectively detect the target signal in the mixed jamming. [ABSTRACT FROM AUTHOR]

This work studies the direct wave suppression technology of passive radar system based on 'global system for mobile (GSM)' communication. In order to suppress direct waves, this study proposes an adaptive suppression algorithm based on NLMS criterion. Achieves great suppression of the strong interference signal, and finally realised target positioning and velocity measurement to the actual measured GSM signal. [ABSTRACT FROM AUTHOR]

The mainlobe interference is a noticeable issue in the passive bistatic radar. As the direction of arrival (DOA) of the interference is close to the DOA of the target echo, the interference hardly be cancelled by the adaptive spatial filtering. After clutter cancellation, the authors assume the mainlobe interference is the principal component of the array element signal. This study proposes the method based on the principal component analysis (PCA) and the extensive cancellation algorithm (ECA) to cancel the mainlobe interference in the echoes. The PCA is applied to extract the interference component from the array element signals, and the ECA is applied to cancel the interference with the extracted interference component as the reference. Finally, the simulation result proves the feasibility of the method proposed by this paper. [ABSTRACT FROM AUTHOR]

Deceptive jamming is an effective jamming method for synthetic aperture radar (SAR). Time-delay repeater jamming, which is an important method of deceptive jamming because of its simplicity and effectiveness, can generate false targets in the SAR image and further affect the image interpretation. To detect the false target, this study first establishes the multi-angle SAR jamming signal model. Subsequently, the representations of the false targets and real targets in SAR image are analysed. Based on the aforementioned analysis, a SAR deceptive jamming target detection method based on multi-angle SAR images is proposed. Through the registration of multi-angle SAR images and the change detection, the false targets generated by the time-delay repeater jamming can be detected, and the SAR anti-jamming can be realised correspondingly. Computer simulation verifies the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The interference of the multipath spreading among the targets and the interior walls will be introduced into the radar image. This study mainly deals with the multipath suppression problem in three-dimensional (3D) through-the-wall radar imaging. The authors propose a correlation-matching multipath suppression algorithm to eliminate the first-order back wall multipath ghosts. Specifically, they first extract the barycentre coordinates of all objects in the original radar image. Second, a decision criterion is provided to measure the relevance between these objects. If two objects are closely related, they assert that they have multipath-target relationship. Finally, they eliminate the multipath ghosts after all objects being determined. At the analysis stage, they assess the effectiveness of the proposed approach through simulation results, which shows its ability of well-removing multipath ghosts. [ABSTRACT FROM AUTHOR]

Existing radars for stationary human detection need to process echo data from all channels simultaneously, which requires the radar system with high performance. Another limitation of existing technology is poor positioning due to sidelobe interference. Here, a time-division ultra-wideband multiple-input multiple-output (MIMO) radar is presented for stationary human detection using the incoherence of respiratory echoes. Based on the delay-and-summation imaging method, the maximum coherence factor (MCF) is weighted to suppress sidelobe, band-pass incoherence factor is weighted to distinguish stationary objects and human targets, and the variance factor is weighted to achieve accurate positioning. Experimental results show that this method can effectively suppress the noise, filter off the echo of the stationary object, and provide the distance and azimuth information of hidden human targets accurately. [ABSTRACT FROM AUTHOR]

For moving ship detection in synthetic aperture radar (SAR) images, ship wakes on the sea surface may be detectable, thus leading to interferences in reconnaissance. To address this issue, a wake region detection approach by using multi-feature recombination and area-based morphological analysis is proposed with along-track interferogram-SAR systems. This approach aims to detect the near-ship wake region that is nearby a ship's hull and between two kelvin cusp lines. A novel test is constructed by recombining magnitude, phase, and the local variance of phase in the complex multi-look interferometric SAR image to detect the potential pixels of the ship wakes. Then, with a clustering algorithm based on the proposed test and the pixel spatial distance, the potential wake regions are acquired, and the real ones having sufficiently large areas can be accurately determined. Finally, experimental results on the TerraSAR-X dataset validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

To achieve verisimilar target deceptive jamming effect, the jamming signals from different targets in different kinds of situation must be acquired. However, it is difficult to be implemented by the methods using deception-template model. In this letter, a novel target deception jamming method against spaceborne synthetic aperture radar based on electromagnetic (EM) simulation is presented. To improve the computational efficiency, an equivalent bistatic scattered fields are used to simulate the scattering characteristics of false target. The proposed method, which consists of the computer-aided-design model, the deceptive jamming model and the involved EM scattered fields, improves the performance of deceptive target in achieving the jamming results. The simulation results demonstrate the validity of the proposed method. [ABSTRACT FROM AUTHOR]

To solve the problem of the low rate of template matching (TM) jamming decision method under the incomplete jamming rule library condition in traditional electronic warfare, a clustering and resampling – support vector machine (CRS-SVM) jamming decision method, is proposed. For the air-to-air scene of airborne multifunctional fire control radar, the inter-pulse pulse and intra-pulse features are extracted, and a jamming rule library that is divided into the source domain and target domain sample according to the missing rate is constructed in this scene. DBSCAN algorithm is used to cluster the dataset, and the structure information is found. The training samples are generated via resampling. SVM is used to transform the inner product of the target domain space into the inner product of the feature space to establish the feature space hyperplane. The target domain samples are labelled as the corresponding jamming style label to realise the fast and effective decision. The experiment results show that the proposed method can effectively improve the accuracy and robustness of jamming decision compared with the traditional TM method. [ABSTRACT FROM AUTHOR]

Aimed at the problem that the deceptive jamming against synthetic aperture radar ground moving target indication generated by single jammer cannot work effectively in multi-channel SAR, a novel deceptive jamming against multi-channel SAR-GMTI based on two jammers is studied. First, signal model of the novel deceptive jamming is built. Then, based on three-channel clutter suppression and interferometry processing, the amplitude and interferometric phase of deceptive moving target generated by the novel deceptive jamming are derived. Last, simulation experiment validates that the novel deceptive jamming can generate false moving targets with the controllable radial velocity and located azimuth position in the multi-channel SAR. [ABSTRACT FROM AUTHOR]

Interrupted sampling repeater jamming (ISRJ) uses the under sampling technology to transmit and repeat the radar intercepted signals. As a new kind of coherent interference, it is widely used in self-defence interference. At the same time, the existing radar anti-jamming technology cannot effectively combat it. In this study, the principle of ISRJ is analysed. In view of the mismatch between the jamming signal and the radar transmitting signal, an orthogonal phase-frequency coded signal in a pulse is designed. In signal processing, matching and filtering are processed separately through each sub-signal. The simulation results show that the designed signal has a good inhibitory effect on ISRJ. [ABSTRACT FROM AUTHOR]

Based on digital radio frequency memory technology, jammers can copy the radar signal multiple times by different time delay and frequency shift to form deceptive multiple false targets. For non-self-defensive-type main lobe jamming, the jamming signal and the real signal from different angles into the radar receiver, when the false target generated by the jammer was in the same range cell as the real target, the angle measurement result was with high probability in the energy centre between the target and jamming. Thus, the angle tracking performance of the monopulse radar was retrograded. In this study, an anti-jamming method called angle inversion based on power synthesis is proposed to effectively estimate the real perspective of the target from deceptive multiple false targets, and the anti-jamming performance is revealed under the condition of a different jammer-to-signal ratio. [ABSTRACT FROM AUTHOR]

Multipath interference is the main factor which has influence in super-low-altitude detection. Aiming at solving the problem of detection for super-low-altitude target, anti-multipath methods under concrete environment are studied here. First, antenna radiation pattern of seeker is introduced to modify traditional four-path method. Then, the hybrid method combining physical optics (PO) and method of equivalent currents (MEC) is used to calculate the scattering electric field of target. Compared to the method of moment (MoM), the PO + MEC hybrid methods are of high accuracy. Finally, the multipath interference scattering from interaction between the target and the environment under the condition is studied and analysed in detain. The simulation results are useful in military application. [ABSTRACT FROM AUTHOR]

In this article, an anti-jamming technique based on homologous localisation test in multi-static radar system is proposed to counter multi-range-false-target deception jamming. At first, pre-process is implemented in each receiver to group the targets that locate in the same direction and improve the accuracy of angle measurement. Then, the localisation of bistatic radar system is performed. Finally, homologous localisation test is implemented in fusion centre by using the localisation results from all the receivers. Simulation results demonstrate that the proposed suppression method can discriminate false targets effectively and realise the localisation of the true target. [ABSTRACT FROM AUTHOR]

Towed decoy can simulate the time domain and frequency domain characteristics of target in radar beam and form effective angle deception. In order to improve the radar ability to countermeasure towed decoy, this study extracts and uses the radar diagonal difference channel in the conventional monopulse radar. The characteristic of diagonal difference channel is analysed. Then, the equations of sum channel, azimuth difference channel, elevation difference channel, and diagonal difference channel are established. By solving the equations, the angles and amplitude of decoy and target are obtained. Decoy recognition method is proposed. The new method can obtain the angles of decoy and target using only one pulse, and recognise decoy steadily using several pulses. The simulation results confirm the effectiveness of the new method. [ABSTRACT FROM AUTHOR]

The suppression of mainlobe jamming (MLJ) is a hard task and an open problem in the electronic counter-countermeasures field. In this article, a sparse Bayesian learning (SBL)-based mainlobe blanket jamming suppression algorithm is proposed for solving this problem, which can effectively suppress the MLJ and estimate the target distance and direction. The proposed algorithm can be divided into two steps. First, the row (or column) spatial adaptive processing is adopted to suppress the MLJ; Second, the SBL algorithm is used to obtain the target echo parameters. [ABSTRACT FROM AUTHOR]

Adaptive monopulse approaches for angularly localising a main-beam target in jamming are usually based on variations of the concept of optimising the sum (Σ) beam via standard adaptation and then optimising the delta (Δ) beam subject to maintain the monopulse slope. These methods have some deficiencies: they do not address target self-nulling issues; they lack tapering, leading to high sidelobes; they introduce multiple point constraints, which may result in target leakage; and they assume linearity of the monopulse ratio curve, something valid only in a small region close to the beam steering direction. The method of this study addresses these and other concerns by maintaining tapered Σ and Δ beams and fully preserving their mainlobes while adaptively suppressing jammers. This approach provides the added bonus of enabling operating in the monopulse curve's non-linear region at wider beamwidths, hence also increasing the efficiency of radar searching and tracking functions. It is shown that such approach is extremely robust and flexible, as it avoids target self-nulling effects due to beam mispointing, it is immune to target and interference dithering effects, and it can be easily extended for super-resolving multiple main-beam targets. [ABSTRACT FROM AUTHOR]

The coherent nature of radar illumination causes the speckle effect, which gives the synthetic aperture radar (SAR) image its noisy appearance. The probability distribution of speckle noise is multiplicative rather than additive, which makes the interpretation and processing of SAR imagery more difficult. A novel SAR image denoising method is proposed. First the multiplicative noise is transformed into additive-like noise by logarithmic transformation. After that, a novel object function is proposed which combines a pre-trained dictionary model to deal with the image. Finally, exponential transform is employed to recover the image. Experimental results show that the proposed method can effectively remove the noise of SAR images, and indicate good performance compared with other state-of-the-art methods. [ABSTRACT FROM AUTHOR]

When high-frequency continuous wave (HFCW) radars transmit linear frequency modulated (LFM) continuous wave, there will be direct wave (DW) interference due to temporal continuity. In order to prevent receiver saturation, a DW cancellation system device is developed. This study studies the theoretical model of RF cancellation and derives the DW cancellation ratio formula. Afterwards, a system design scheme for DW cancellation is proposed, where the design and system control algorithms of each module of the cancellation system are mainly studied. Finally, by analysing the DW cancellation technique under multipath effect, it is found that the multipath effect will affect the depth of cancellation. The simulation results verify the correctness of the system design method, the measurement shows a leakage suppression of >15 dB under multipath effects. [ABSTRACT FROM AUTHOR]

Conformal arrays are widely used in various aircrafts since they do not affect the aerodynamic performance of the carriers. When conformal arrays are used to suppress fast-moving interference, it is possible that the weight mismatches the data of measurement due to the perturbation of the interference location. Traditional null widening methods are based on linear or planar arrays and cannot be applied to conformal arrays directly. Therefore, a null widening method used for conformal arrays is proposed in this article. In the method, the spatial spectrum of the signal is first calculated, and then the convolution of spatial spectrum in the interference region and 2-D window function is calculated to enhance the spatial spectrum. Next, the enhanced covariance matrix is calculated based on the convolution results. Finally, the sample matrix inversion (SMI) method is used to calculate the weight. This method can be used for common conformal arrays and can form two-dimensional nulls in space. Based on the numeral simulation results, it is verified that the proposed method can form widened nulls and improve the robustness of interference suppression effectively. [ABSTRACT FROM AUTHOR]

The amplitude-phase error caused by the channel inconsistency in the actual digital array radar and the mutual coupling error caused by the mutual coupling effect have a great influence on the performance of the array. This study analyses and models the error characteristics of amplitude-phase error and mutual-coupling error, respectively. Based on the narrow-band and wide-band array received signal models, the spatial signal arrival angle estimation accuracy and the beam-synthesising pattern are used as indicators to analyse the influence of errors on the array. Channel inconsistency and mutual coupling will cause the estimated signal arrival angle to deviate from the true signal direction and the spatial spectrum curve peak will become gentle. In addition, the beam pattern's sidelobe will raise, null orientation will deviate from the interference signal direction, and gain will raise. [ABSTRACT FROM AUTHOR]

Pseudo-random sequence plays an important role in the field of the phase noise simulation. This study analyses the pseudo-random sequence generated by the method based on cellular automata (CA). Compared with the method of look-up table and linear feedback neighbourhood registers, the simulation results show that the pseudo-random sequence generated by the CA method has better adaptability in the process of phase noise simulation. [ABSTRACT FROM AUTHOR]

The electronic counter countermeasures (ECCM) technology is crucial to the modern airborne radar. In this study, opposed to the intelligent electronic countermeasure system, an intelligent anti-jamming technology is developed, which adjusts the working parameters and ECCM steps in real time and optimises the radar performance in various jamming scenarios. The framework of the proposed intelligent anti-jamming technology includes the cognitive jamming detection and suppression, adaptive frequency agility, and waveform diversity. The application of the proposed technology in the airborne radar is analysed via numerical simulations. [ABSTRACT FROM AUTHOR]

Dense false target jamming can affect radar detection performance severely. A method of dense false targets jamming recognition based on time-frequency atomic decomposition theory and support vector machine (SVM) is proposed to solve the difficulty of dense false targets jamming identification. According to the feature of ambiguity function of dense false targets jamming signal, a Gabor sub-dictionary which has adaptive variation with signal is designed. The signal is expanded into the corresponding Gabor time-frequency dictionary by sparse decomposition. After Gabor atomic time-frequency parameters are extracted as individual feature vectors, SVM is utilised for classification and recognition. The experimental results show that the extracted Gabor atomic time-frequency parameters can effectively represent the essential features of target and dense false targets jamming, respectively, and this method has a high recognition rate. [ABSTRACT FROM AUTHOR]

The architecture and processing algorithm of mainlobe interference suppression method is described for nulling the signal from mainlobe electronic jammer and multiple sidelobe electronic jammers while maintaining monopulse angle estimation accuracy on the target. The existing mainlobe interference suppression method is based on monopulse Wiener filtering. However, the Wiener filtering is more suitable to remove static interference. Therefore, the authors present the dynamic mainlobe interference suppression method with Gray Model Kalman filter to resolve this problem. The simulations verify the proposed method. [ABSTRACT FROM AUTHOR]

Inter-radar interference will be a crucial problem when a number of frequency modulated continuous wave (FMCW) radars are densely deployed in future, since it can cause miss detection and false detection of the target due to wideband interference and narrowband interference. One of the approaches to solve this problem is to introduce a multiple access technique for automotive radars, e.g. carrier sense multiple access used in wireless LAN to avoid packet collision. This study proposes multiple access FMCW radar which can avoid both narrow-band and wideband interference assuming all of the FMCW radars have the same design parameters. It also, proposes a carrier sense technique as a key technique for multiple access FMCW radar and evaluates the carrier sense performance by computer simulations. [ABSTRACT FROM AUTHOR]

To distinguish/detect multiple close targets is of great significance in many areas, and the typical tool is the GLRT detection. However, there will be distinguishing difficulty and mutual interference when present targets are very close. Furthermore, it is difficult for binary decision theory to tell where the targets locate exactly as it can only make a decision that whether there is one or two targets present. As it cannot utilise the prior information of target number, it also suffers a poor detection performance. To overcome those disadvantages, the authors bring in multi-hypothesis test (MHT) to the multi-target model within co-located MIMO radar. They also apply the sequential probability ratio test (SPRT) to locate the multiple range-located targets efficiently, whose angles are known as a prior. The simulations show that authors' SPRT-based detection is more fast and constant comparing to the existing GLRT-based detection taken within cell-by-cell. [ABSTRACT FROM AUTHOR]

The multipath transmission has a serious effect on jamming efficiency in a short distance ECM task for wideband ground radars. After the sidelobe gain model for a large antenna is introduced, the characteristics of multipath channel in time and frequency domain are analysed. The statistical characteristics about the amplitude change of the intercepted pulse signals and the occurrence conditions of frequency selective fading are explained. The short time compatibility between reconnaissance channel and jamming channel is used to pre-distort the jamming signal, and the serious influence of multipath transmission on the jamming signal is greatly eliminated. The fidelity of deception jamming on the radar is greatly improved. The validity of theoretical analysis is verified by simulation experiments. It provides an important theoretical guidance for a short distance electronic counter measures (ECM) task against ground radars. [ABSTRACT FROM AUTHOR]

Based on the purpose of proactive anti-reconnaissance, the essential characteristics of several typical pulse repetition interval (PRI) sorting algorithms were analysed and the feasibility of counter-deinterleaving was discussed. A method for disturbing arrival time sequence by using interference pulse was proposed, which changes the statistical properties of the radar PRI to disturb the deinterleaving results. The simulation results show that the pulse jamming method proposed in this paper can influence PRI sorting process effectively, which let signal processer make a misjudgment on PRI pattern of radar. [ABSTRACT FROM AUTHOR]

This article designs waveform in fast-time domain to optimise high-frequency radar performances embedded in the co-channel interference and coloured noise. Considering the whitening filter is applied for fast-time processing, a novel objective function accounting for both signal to interference plus noise ratio (SINR) and integrated range sidelobe level (IRSL) is introduced and the constant modulus constraint is forced on the probing waveform. An iterative algorithm based on the alternating direction method of multipliers is presented, resolving such non-convex quartic optimisation problem with a polynomial-time computational complexity. In each iteration, two quadratic problems are presented, with the closed-form solutions given. Finally, the authors evaluate the effectiveness of the designed waveform in terms of the range-Doppler processing result, SINR, IRSL and power spectrum. [ABSTRACT FROM AUTHOR]

Aiming at the problem that azimuth cosinusoidal phase-modulation cannot be directly implemented in application, and two-dimensional modulation can only be carried out in azimuth and distance, respectively, a joint azimuth-range jamming method based on time delay for ISAR is proposed. The ISAR signal captured by jammer is delayed in the fast time domain. The ISAR signal captured by jammer is then delayed in the fast time domain to achieve the cosinusoidal phase-modulation because the time delay is a function of slow time. The blind frequency shift modulation term is introduced at the same time. The simulation results show that the target will be completely submerged in the multiple jamming strips formed by the jamming signal, and the feasibility and effectiveness of the method are verified. [ABSTRACT FROM AUTHOR]

The scattered-wave sweeping frequency jamming occupies many space-time adaptive processing (STAP) degrees of freedom, which results in a serious decline in STAP performance. To solve this problem, an anti-jamming method of STAP based on a bi-phase random-coded signal is proposed. This method utilises the phase-coded signal's ability of waveform agile and anti-jamming. Also, the phase coding is designed as a random sequence, which distinguishes and suppresses the interference by white noise characteristic. Simulation results show that, compared with the STAP method based on a chirp signal, the proposed method improves beamforming robustness and clutter suppression capability under an interfering background. [ABSTRACT FROM AUTHOR]