Fuzzy Jamming Pattern Recognition Based on Statistic Parameters of Signal’s PSD

In order to recognize the jamming pattern in anti-jamming, a novel fuzzy jamming recognition method based on statistic parameters of received signal’s power spectral density (PSD) is proposed. It exploits PSD’s shape factor and skewness of received signal as classified characters of jamming pattern. After the mean center and variance of each jamming pattern are calculated by using some jamming samples, an exponential fuzzy membership function is used to calculate the membership value of the recognized sampl...     

A GNSS Signal Blind-decoding Algorithm at Low SNR

The pseudo-random noise (PRN) code modulated in satellite navigation signals impacts the system positioning performance directly, and the code monitoring is one of the key technologies. However, the received signal is often buried in noise, and the ranging codes can not visible in time domain. Considering local clock bias, the signal model in transmission link is derived in this paper, and a PRN code blind-decoding method is proposed also. It calculates the signal’s cyclic spectrum by using fast Fourier tra...     

Research of the Adaptive Beamformer Based on the Frequency Energy Normalization

An algorithm of broadband minimum variance distortionless response （MVDR） based on the frequency energy normalization is proposed. First, every narrowband frequency component of the broadband signal is normalized by the total narrowband energy of all array elements, and the narrowband power is calculated by MVDR. Finally, final spatial energy spectrum can be obtained by averaging or summing all results of every narrowband frequency bin. Any prior-information about the noise or the signal is unnecessary for the proposed method in this paper. The processing gain of the proposed method compared to the conventional broadband MVDR can be obtained as long as the amplitude fluctuation of the array noise frequency spectrum is severer than that of the target signal. The validity of the method is validated by the optimal signal detection theory. Simulation and real data are used to validate the performance of the method. Analysis results show that about 4 dB processing gain compared to the general broadband MVDR can be reached by the proposed method.     

Single channel source separation of radar fuze mixed signal based on phasedifference analysis

A new method based on phase difference analysis is proposed for the single-channel mixed signal separation of single-channel radar fuze. This method is used to estimate the mixing coefficients of de-noised signals through the cumulants of mixed signals, solve the candidate data set by the mixing coefficients and signal analytical form, and resolve the problem of vector ambiguity by analyzing the phase differences. The signal separation is realized by exchanging data of the solutions. The waveform similarity coefficients are calculated, and the timeefrequency distributions of separated signals are analyzed. The results show that the proposed method is effective. Copyright . 2014, China Ordnance Society. Production and hosting by Elsevier B.V. All rights reserved.     

Detection Algorithm for LFM Echo of Underwater Moving Targets Based on Discrete Fractional Fourier Transform

The mismatch between echo and replica caused by underwater moving target（UMT）＇s radial velocity degrades the detection performance of the matched filter（MF） for the linear frequency modulation（LFM） signal. By using the focusing property of fractional Fourier transform（FRFT） to that signal, a detection algorithm for UMT＇s LFM echo based on the discrete fractional Fourier transform（DFRFT） is proposed. This algorithm is less affected by the target＇s radial velocity compared with the other MF detection algorithm utilizing zero radial velocity replica（ZRVR）, and the mathematical relation between the output peak positions of these two algorithms exists in the case of existence of target echo. The algorithm can also estimate the target distance by using this relation. The simulation and experiment show that this algorithm＇s detection performance is better than or equivalent to that of the other MF algorithm utilizing ZRVR for the LFM echo of UMT with unknown radial velocity under reverberation noise background.     

Statistics Modeling of Shallow Sea Ambient Noise and Its Applications in Low-frequency Line Spectrum Detection

The noise’s statistical characteristics are very important for signal detection.In this paper,the ambient noise statistical characteristics are investigated by using the recorded noise data in sea trials first,and the results show that the generalized Gaussian distribution is a suitable model for the ambient noise modeling.Thereafter,the optimal detector based on maximum likelihood ratio can be deduced,and the asymptotic detector is also derived under weak signal assumption.The detector’s performance is verified by using numerical simulation,and the results showthat the optimal and asymptotic detectors outperform the conventional correlation-integration system due to accuracy modeling of ambient noise.     

Adaptive Signal Conditioning Technology in Fighter Weapon System Test

In order to realize the real-time and precise test for a weapon system of a certain type of fighter, a signal classification method according to attributes is proposed, common input channels for multiple signals are configured optimally, and a test adapter and an adaptive signal conditioning module is designed. The hardware of conditioning module can be configured flexibly and the programmable test range can be adjusted owing to programmable multiplexer. An FPGA adaptive filter is designed by the calculated filter coefficient vectors with LMS method to solve the problem of parallel test of fighter weapon system in electromagnetic interference environment. The adaptive signal conditioning technology is characterized by high efficiency, precision and integration. Its application makes the test system successful to conduct real-time and parallel test for a weapon system, which is developed based on VXI bus and virtual-instrument technology.     

A Classification Algorithm for Ground Moving Targets Based on Magnetic Sensors

A novel classification algorithm based on abnormal magnetic signals is proposed for ground moving targets which are made of ferromagnetic material. According to the effect of diverse targets on earth's magnetism,the moving targets are detected by a magnetic sensor and classified with a simple computation method. The detection sensor is used for collecting a disturbance signal of earth magnetic field from an undetermined target. An optimum category match pattern of target signature is tested by training some statistical samples and designing a classification machine. Three ordinary targets are researched in the paper. The experimental results show that the algorithm has a low computation cost and a better sorting accuracy. This classification method can be applied to ground reconnaissance and target intrusion detection.     

Real-time Extraction of Target Position Information Based on Bi-orthogonal Wavelets

Extraction of flying target position information is the prerequisite for passive infrared guided missiles to track the target. The existing missile detection system senses the target＇ s infrared radiation, and then the generated signal is sent to signal processing circuits for extracting the target position information. In order to improve anti-interference capacity of the detection system, an algorithm of module maximum edge detection based on the bi-orthogonal wavelets is proposed to replace its hardware. The signal can be decomposed in one layer, only its high frequency detail is reconstructed. After some calculations, the average target position can be obtained. The algorithm＇s real-time implementation with DSP is also discussed. To reduce the execution time, the program structure can be optimized with double buffers in memory. This im- plementation is verified by simulations. The results show that the method has only a small amount of calculations, can meet the requirements for finding out the target position in real-time and needs not the traditional processing circuit.     

An Orthogonal Wavelet Transform Fractionally Spaced Blind Equalization Algorithm Based on the Optimization of Genetic Algorithm

An orthogonal wavelet transform fractionally spaced blind equalization algorithm based on the optimization of genetic algorithm(WTFSE-GA) is proposed in viewof the lowconvergence rate,large steady-state mean square error and local convergence of traditional constant modulus blind equalization algorithm(CMA).The proposed algorithm can reduce the signal autocorrelation through the orthogonal wavelet transform of input signal of fractionally spaced blind equalizer,and decrease the possibility of CMA local convergence by using the global random search characteristics of genetic algorithm to optimize the equalizer weight vector.The proposed algorithm has the faster convergence rate and smaller mean square error compared with FSE and WT-FSE.The efficiency of the proposed algorithm is proved by computer simulation of underwater acoustic channels.     

Method of Infrared Image Enhancement Based on Stationary Wavelet Transform

Aiming at the problem,i.e.infrared images own the characters of bad contrast ratio and fuzzy edges,a method to enhance the contrast of infrared image is given,which is based on stationary wavelet transform.After making stationary wavelet transform to an infrared image,denoising is done by the proposed method of double-threshold shrinkage in detail coefficient matrixes that have high noisy intensity.For the approximation coefficient matrix with low noisy intensity,enhancement is done by the proposed method based on histogram.The enhanced image can be got by wavelet coefficient reconstruction.Furthermore,an evaluation criterion of enhancement performance is introduced.The results show that this algorithm ensures target enhancement and restrains additive Gauss white noise effectively.At the same time,its amount of calculation is small and operation speed is fast.     

Evaluation for Success Probability of Chaff Centroid Jamming

As the chaff centroid jamming can introduce the guiding error of the anti-warship missile＇s seeker and decrease its hitting probability,a new quantitative analysis method and a mathematic model are proposed in this paper to evaluate the success jamming probability.By using this method,the optimal decision scheme of chaff centroid jamming in different threat situations can be found,and also the success probability of this scheme can be calculated quantitatively.Thus,the operation rules of the centroid jamming and the tactical approach for increasing the success probability can be determined.     

An Automatic Interference Recognition Method in Spread Spectrum Communication System

An algorithm to detect and recognize interferences embedded in a direct sequence spread spectrum （DSSS） communication system is proposed. Based on Welch＇ s averaging modified periodogram method and fractional Fourier transfor- mation （FRFT）, the paper proposes a decision tree-based algorithm in which a set of decision criteria for identifying different types of interferences is developed. Simulation results demonstrate that the proposed algorithm provides a high recognition rate and is robust for various ISR and SNR.     

Research on Integrated Analysis Method for Equipment and Tactics Based on Intervention Strategy Discussion

As the increase of the complexity of the information warfare,its intervention strategy needs to be designed in an integrated environment.However,the current research always breaks the internal relation between equipment and tactics,and it is difficult to meet the requirements of their integrated analysis.In this paper,the research status quo of the integrated analysis about equipment and tactics is discussed first,some shortages of the current methods are summarized then,and an evolvement mechanism of the integrated analysis for equipment and tactics is given finally.Based on these,a framework of integrated analysis is proposed.This method’s effectiveness is validated by an example.     

Fault Diagnosis Method Based on Fractal Theory and Its Application in Wind Power Systems

The non-linear dynamic theory brought a new method for recognizing and predicting complex non-linear dynamic behaviors. The non-linear behavior of vibration signals can be described by using fractal dimension quantitatively. In this paper, a fractal dimension calculation method for discrete signals in the fractal theory was applied to extract the fractal dimension feature vectors and classified various fault types. Based on the wavelet packet transform, the energy feature vectors were extracted after the vibration signal was decomposed and reconstructed. Then, a wavelet neural network was used to recognize the mechanical faults. Finally, the fault diagnosis for a wind power system was taken as an example to show the method’s feasibility.     

A Study on Missile Reentry Control Based on the Method of Feedback Linearization

In the process of missile large attack angle reentry, there exist nonlinear, strong coupling uncertainty and muhiinput-multi-output （MIMO） in the movement equations, so the traditional small disturbance faces difficulties. For such situations, the method of feedback linearization is adopted to control the complex system, and the control method based on the fuzzy adaptive nonlinear dynamic inversion decoupling control of missile is proposed in the paper. According to the principle of time-scale separation, the system is separated into fast loop and slow loop, the method of dynamic inversion is applied to them, and the method of adaptive fuzzy approach is adopted to compensate for the uncertainty of the fast loop. The simulation results denote the. control method in the paper has a better tracing characteristic and robustness.     

Research on Airborne Electro-Optical Tracking and Sighting System Based on Fuzzy PID and H∞ Control

Airborne electro-optical tracking and sighting system is a three-degree-of-freedom angular position servo system which is influenced by multi-disturbance, and its control system consists of stabilizing and tracking components. Stabilizing control is applied to track angular velocity order and control multi-disturbance under airborne condition, and its robustness should be very good; tracking control is applied to compensate tracking error of angular position. A mathematical model is established by taking the control of yaw loop as example. H∞ stabilizing controller is designed by taking the advantage of H∞ control robustness and combining with Kalman filter. A fuzzy control is introduced in general PID control to design a decoupled fuzzy Smith estimating PID controller for tracking control. Simulation research shows that the control effect of airborne electro-optical tracking and sighting system based on fuzzy PID and H∞ control is good, especially when the model parameters change and the multi-disturbance exists, the system capability has little fall, but this system still can effectively track a target.     

Study on Quadratic Effect Assessment of Vulnerability of Military Aircraft Under Multiple Hits

Under the conditions of multiple hits and quadratic effects,the aircraft vulnerability assessment method is proposed by means of kill-tree diagram and state transition matrix.Four instances of the quadratic effects are investigated：non-redundant components to non-redundant components,non-redundant to redundant,redundant to non-redundant and redundant to redundant.The application of the proposed method to the calculation of quadratic effects is also studied.     

A New Synthesis Method for Sum and Difference Beam Pattern with Low Sidelobe

A new method for sum and difference beam pattern synthesis with low sidelobe is proposed.In the situation of phase taper weighting,it makes use of Fourier transform pair relationship existing between the array factor and the element excitations and uses a loop iterative way to derive the array element excitations according to given array factor.The iteration does not stop until the array element excitations meet the initial sidelobe requirements.The method overcomes the defects of traditional methods,such as more searching times,larger amount of calculation and poor robustness.In addition,it can also synthesize the low sidelobe pattern in case of element failures.Simulation verifies the effectiveness of the method.     

The Spatial Color Mixing Model of Digital Camouflage Pattern

A spatial color-mixing model based on tricolor angular frequencies is proposed in consideration that the design theory falls behind the application of digital camouflage pattern. The model is based on Fourier transform and Gaussian low-pass filter （LPF）. In the model, the tricolor angular frequencies are introduced to the spatial frequency response function of human color vision, and the effects of atmospheric attenuation and air screen brightness on color mixture are considered. The field test shows that the model can simulate the color-mixing process in the aspects of color-mixing order, and shape and position of color-mixing improved by optimizing the atmospheric parameters and tricolor cut-off digital camouflage pattern. spot. But the color-mixing spot color is not perfect, which can be angular frequencies. The model provides a tool for the research on