Harmonic wave radar seeker target micro-motion recognition

Correlation filters have been used very successfully in automatic target recognition (ATR) applications for ground- based tactical targets. Specifically, the maximum average correlation height filter has shown excellent performance in target detection and aimpoint selection for various types of armored vehicles in cluttered environments. This type of ATR is particularly well suited for implementation in an optical correlator due to the use of Fourier domain processing. We report preliminary test results of this type of SDF filter against ballistic missile defense targets and evaluate it in the context of real-time missile system performance.

With the development of the ballistic missile defense penetration technology, the reentry ballistic missile can be maneuverable to change its trajectory in order to achieve defense penetration. Besides the air resistance, the maneuvering force generated by missile causes the abrupt change of acceleration during the reentry duration, so in order to obtain better tracking performance, it's necessary to improve nonlinear filters' adaptability to such maneuver. The paper puts forward a self-adaptive EKF/UKF with attenuation memory maneuver detection based on the conventional EKF /UKF algorithm. When the ballistic missile targets do not change its trajectory on reentry, the filtering precision of UKF is higher than that of EKF, and meanwhile the prior information of the ballistic coefficient can improve the filtering precision and stability. To track the targets which can make trajectory-change for defense penetration, the standard EKF and the standard UKF both have large filtering deviation. However, through maneuver detection and adaptive adjustment of the process noise convariance matrix in time, the self-adaptive EKF/UKF can reduce the filtering error caused by the abrupt acceleration change evidently, and attain a much higher filtering precision and enhanced robustness. The simulation results validate this method.

The micro-motion Doppler echo simulation and characteristic parameter extraction of the extended micro-motion target are carried out. For the extended micro-motion target, the echo from the target cannot be regarded as several points' echo. Based on the connections between the scattering field and Doppler echo, an echo simulation method for micro-motion target (based on physical optics) and a method of equivalent current are proposed. At the moment, the micro-motion target can be taken as a static target, so the back scattering field series can be calculated by physical optics and the method of equivalent current. The back scattering field series calculated in the target coordinate system is transformed into the echo of radar coordinate system by the conversion of coordinates, and the Doppler echo is obtained. By comparing with the analytic signal model, the method is validated. The precession characteristics of a cone and warhead with fins are analyzed. Echoes come from every part of the extended micro-motion target and contain the motion characteristics of that part. So the traditional time-frequency analytical methods are not appropriate. In order to achieve better time frequency concentration and avoid the cross terms, the S-method is used to get the time-frequency distributions. The time-frequency characteristics at different radar waves' incidence angles, target different motion states and different geometries are analyzed. From the time-frequency distribution map, the micro-motion of the cone behaves as the micro-motion of two strong scattering points at the bottom of the cone. Because of the shielding effect, the time-frequency curves are not integrated when the radar waves are incident from the cone's bottom. The sinusoidal curve can be mapped to a point in the parameter space based on the inverse radon transform, and the target micro-motion parameters can be obtained. Results of inverse radon transform also show that the precession of the cone behaves as the precession of the two strong scattering points, and the two points' phase difference is equal. For warhead with fins, the time frequency distribution of spin behaves as four sinusoidal curves whose phase differences are equal, implying that the micro-motion of the target behaves like the four fins' micro-motion. However, the sinusoidal curves of precession of the warhead with fins are very different, i.e. their phase differences are not equal. This is because the precession consists of spinning and coning, and the coning has a modulation effect on the spinning. These phase information and the number of strong scattering points can be directly and easily obtained through inverse radon transform. This study combines the electromagnetic scattering with the signal procession. And some results are different from that of traditional micro-motion models through the simulation of typical ballistic targets. Results are explained and analyzed by combining scattering theory. This research has important theoretical and application values in the ballistic target detection and recognition.

This paper establishes a mathematical model based on the initial position and trajectory of enemy missiles, the positions of our real and decoy targets, the initial position of drones, the number of smoke grenades carried, deployment and detonation timing, and drone allocation. The model aims to find a global optimal solution to enhance the effective coverage duration of smoke clouds and improve drone combat effectiveness. For Problem 1, we first establish mathematical models for drone deployment of smoke interference grenades for enemy missiles M1, drones MY1, real targets, and decoy targets. Subsequently, we calculate their positions at any moment using relevant motion models. Finally, through a line-of-sight (LOS) occlusion model, real targets are abstracted into 16 test points to determine whether missile line-of-sight can be effectively occluded at any moment. The effective coverage duration is calculated by subtracting the initial and final times of effective occlusion. For Problem 2, we first define approximate ranges for four parameters: FY1's flight direction, speed, smoke interference grenade deployment point, and detonation point. We then narrow these parameter ranges using binary search and iteratively solve the objective function for these four parameters using an Evolutionary Search Genetic Algorithm (ESGA) optimized with an early termination mechanism. Genetic algorithm operations identify the maximum effective occlusion duration, with fitness analysis and patience value comparison used to determine whether early termination is necessary to avoid local optima. Finally, sensitivity analysis is conducted using differential evolution and particle swarm optimization models to verify solution accuracy after accounting for uncertain factors.

As an important passive sensing technology, infrared sensor has been used in satellite remote sensing systems to discriminate exo-atmosphere targets. At a long range, even relatively large objects are represented as single pixels on the IR image. The infrared signature, i.e., the time sequence of the target point's gray level serves as potential discriminants and has been used in many systems to classify the objects. Studying the generative process of the infrared signature is the premise of this research. In this paper, finite element analysis is used to simulate the infrared signature of exo-atmosphere micro-motion object. Modeling the dynamic of surface temperature field of the targets is a critical step. The main contribution of this paper is to analyze the influence of the micro-motion to the modeling of temperature field. Micro-motion is an important characteristic of the ballistic target. The way of motion causes the radiation received by the surface element changes dramatically, which may affect the simulation process. However, to the best of our knowledge, this problem has not been addressed in other papers. Two temperature field modeling techniques, i.e., the explicit and hidden schematic, are assessed at different sampling time steps. The results show that the explicit method is easy to cause oscillating for the micro-motion object. Although the hidden method is able to avoid the oscillating problem, sufficient small sampling time step is still needed to generated stable surface temperature field. The simulated temperature field dynamic shows that the temperatures in the field approach to be the same and do not change much in a short time period. After the temperature field is generated, micro-motion target's infrared signature is also generated.

Midcourse Space Experiment attitude system performance for gyro disabled operations

An analytical study of intense radiation generation at second harmonic frequency, by a circularly polarized laser beam propagating in plasma, in presence of an obliquely applied magnetic field, has been presented. Considering a mildly relativistic regime, a perturbation scheme is used for evaluation of transverse components of current density. The current density oscillating at twice the fundamental frequency of the laser field, drives the second harmonic radiation. The amplitude of the circularly polarized second harmonic radiation is derived and its variation with obliqueness of the applied magnetic field is graphically depicted.

It is a very common custom to use extremely simple target models in specification for radar, radar system design, performance analysis, comparison, and evaluation. While the use of rudimentary models simplifies the work, their use can only result in ultimate disappointment of the radar user, severe illness in the course of the radar development and testing, followed by major surgery, and sometimes a premature death of the program. Consideration of the purposes of radar indicates that its functions are to detect/identify/track real-world targets, not paper targets. Problems in relating simple target models to real-world targets are treated for both aircraft and ballistic targets. Based on proper radar representation, simulation results and data from field performance tests, the inadequacy of simple target models is shown. A number of situations in the design and comparison of radars are given to further illustrate the problem. Special treatment is accorded to "average" radar cross section (RCS). Finally, recommendations are made for target models which more nearly approach the real world and permit an improvement in the design, evaluation, and analytical comparison of radars. It is shown that these models, while giving more valid results, are not necessarily complex and are achievable.

Adaptive quantum design identifies the best broken-symmetry configurations of\natoms and molecules that enable a desired target function response. In this\nwork, numerical optimization is used to design atomic clusters with specified\nquasiparticle densities of states. The dominant self-assembled building blocks\nof these engineered quantum systems are found to depend on the symmetry of the\ntarget function. For example, particle-hole symmetric spectra can be\nconstructed from a dilute configuration of atomic dimers, whereas more complex\nstructures such as trimers and quadrumers are required for asymmetric target\nfunctions. The convergence of the optimization algorithms depends on the shape\nof the target function, the density of atoms, and constraints due to substrates\nand boundary conditions. Hybrids of steepest descent methods, simulated\nannealing, and genetic algorithms are found to be most efficient.\n

This article proposes a jitter-aware decoupling capacitors placement optimization method that uses the genetic algorithm (GA). A novel method for defining the optimization target function in regard to power delivery network (PDN) and power source-induced jitter (PSIJ) optimization based on the GA-based tool is proposed. The proposed method can provide an optimum and economic solution for the number of decoupling capacitors to use in a PDN to reach the target impedance. Then, by modifying the optimization target function with our proposed method, an optimum solution of the number of decoupling capacitors regarding the PSIJ can be obtained. The PSIJ analytical expressions are derived in conjunction with a resonant cavity model that includes the coordinates of the decoupling capacitors and the PSIJ transfer function. The GA-based optimization algorithm with the proposed target function is first applied to optimize the number of decoupling capacitors regarding the PSIJ. Finally, the measured jitters from HSPICE simulation results are used to verify our optimization method such that both the simulated results and analytically calculated results support the efficiency of our proposed optimization method.

Radiation at the harmonic frequencies in free-electron lasers is affected by several factors including misalignment of the electron beam and wiggler axes, and transverse gradients of the electron beam and wiggler field. These processes manifest themselves as changes in the harmonic power and transverse intensity profile. A transverse source function for the monochromatic radiation from a single electron in a plane-polarized wiggler magnetic field is derived that addresses these various effects. The resultant source is a composite of multiply peaked sources distributed over the local transverse wiggle range of each electron where the nth source has n peaks. For transverse-electron-beam density distributions that are slowly varying, an excellent description of the harmonic radiation can be obtained by including only the first few sources. Transverse averages of the distributed sources are taken to make comparisons with previous one-dimensional theories where they exist.

Nonlinear (at the second harmonic frequency of the incident light) optical diffraction by twodimensional lattice of magnetic bubbles (cylindrical magnetic domains) is theoretically studied. Because the periods of these structures are comparable with the wavelengths of the fundamental and the second harmonic radiation, it would be possible to observe diffraction at the second harmonic frequency. We investigate the influence of the value of external magnetic field on the nonlinear magneto-optical diffraction behavior.

When 532 mn light of the second harmonic wave from a pulsed YAG:Nd3+ laser was fed into an a-few-mode fiber, we observed several pairs of the Stokes and anti-Stokes radiations which have different LP modes but same frequency shift from the pumping light. These are generated by the four-photon mixing. This is confirmed by numerical check for the phase matching among the Stokes, anti-Stokes and pumping beams. As the shift increases, it was observed that the Stokes enhances, while the anti-Stokes becomes weak and disappears in a shift region over 250 cm−1 where the Raman gain becomes large. This is concluded to be caused by a competition between the four-photon mixing process and the stimulated Raman scattering process, resulting in the amplification of the Stokes by the stimulated Raman scattering while the absorption of the anti-Stokes by the inverse Raman effect.

The harmonic vibrational frequencies for M(H2O)n (M=Li and Na) are calculated with ab initio molecular orbital (MO) methods. Three types of isomers, surface, quasivalence and semi-internal, exhibit the characteristic frequency shifts ΔνOH. The calculated spectral patterns are related to the geometric conformations around the localized electron {e} in the cluster. The downward shifts of OH frequencies are strongly correlated with the lengthening of OH bond distances, as is well known in the hydrogen bonds. The magnitude of the downward shift is as large as that for the hydrogen bond. The correlation of the shifts with the distance between the center of the electron {e} and the hydrogen atom reveals two types of interaction schemes. The characteristics of the structural unit OH{e}HO in M(H2O)n and its OH modes are common with those found in water anion clusters. The interaction between the localized electron and OH bonds can be called an electron-hydrogen bond.

Acoustic scattering modulation caused by an undulating sea surface on the space–time dimension seriously affects underwater detection and target recognition. Herein, underwater acoustic scattering modulation from a moving rough sea surface is studied based on integral equation and parabolic equation. And with the principles of grating and constructive interference, the mechanism of this acoustic scattering modulation is explained. The periodicity of the interference of moving rough sea surface will lead to the interference of the scattering field at a series of discrete angles, which will form comb-like and frequency-shift characteristics on the intensity and the frequency spectrum of the acoustic scattering field, respectively, which is a high-order Bragg scattering phenomenon. Unlike the conventional Doppler effect, the frequency shifts of the Bragg scattering phenomenon are multiples of the undulating sea surface frequency and are independent of the incident sound wave frequency. Therefore, even if a low-frequency underwater acoustic field is incident, it will produce obvious frequency shifts. Moreover, under the action of ideal sinusoidal waves, swells, fully grown wind waves, unsteady wind waves, or mixed waves, different moving rough sea surfaces create different acoustic scattering processes and possess different frequency shift characteristics. For the swell wave, which tends to be a single harmonic wave, the moving rough sea surface produces more obvious high-order scattering and frequency shifts. The same phenomena are observed on the sea surface under fully grown wind waves, however, the frequency shift slightly offsets the multiple peak frequencies of the wind wave spectrum. Comparing with the swell and fully-grown wind waves, the acoustic scattering and frequency shift are not obvious for the sea surface under unsteady wind waves.