Abstract:Forward scattering radar is a particular bistatic radar scheme with the bistatic angle approaching 180°. According to the total field variation, the forward scattering radar can detect the target when targets pass through the baseline. Therefore, the research on echo characteristics of forward-scattering radar is of great significance. The effects of coherent superposition of scattering and radiation fields are analyzed based on the measurement data of metallic sphere, dihedral, trihedral, and cylinder radar targets in an anechoic chamber. It is summarized that when the radar target enters the forward scattering zone, the echo amplitude decreases firstly, and then rebounds slightly. This work helps to improve the knowledges about forward-scattering radar echo characteristics, and provides supports for the target detection and recognition technologies.

Abstract:In order to verify the effect of Unmanned Aerial Vehicle(UAV) cluster electronic countermeasures, the influence mechanism of cluster ontology, cluster suppression interference, cluster retransmitting interference, and cluster coherent interference on multi-radar parameter measurement is discussed. The influencing factors such as Signal-Noise Ratio(SNR), Jamming-Signal Ratio(JSR), and the amplitude ratio between target echo and UAV body echo are analyzed emphatically. Firstly, the UAV jamming resources are allocated based on the greedy algorithm, and then the influence of several jamming methods on the measurement of radar parameters is analyzed through simulation. The experimental results show that the cluster body has a small effect on the radar, mainly due to the small size of the UAV and the low echo power; the cluster suppression interference increases the detection threshold, which greatly reduces the target detection probability of multiple radars; retransmitting interference can produce a large number of false targets, leading to larger errors in radar angle measurement; cluster coherent interference can cause radar angle measurement to deviate from the direction of the main beam, forming angle deception. Comprehensive analysis shows that the three interference methods, suppression interference, retransmitting interference and coherent interference, have good interference effects when applied in cluster interference.

Abstract:One-dimensional range profile of radar target can be realized by using wide band electromagnetic scattering characteristic data of radar target. In the process of realizing two-dimensional imaging algorithm, the Doppler frequency is required traditionally for azimuth imaging. In this paper, a two-dimensional imaging algorithm based on wideband Radar Cross Section(RCS) static data (without Doppler frequency) is discussed, which breaks through the traditional limitation that Doppler frequency shift data is necessary to realize two-dimensional radar imaging. Finally, several different parameters of imaging algorithm are adjusted for realizing different imaging effects. This work is expected to provide the technical and theoretical supports for different radar imaging application scenarios.

Abstract:Traditional radar detection methods generally detect the target of a range cell as a single target, but do not estimate the number of targets in the range cell. Aiming at this research vacancy, a target number estimation method based on deep residual learning is proposed. The method converts the radar signal into time-frequency graph and inputs it to the trained deep residual network. The residual network can accurately estimate the number of radar targets according to the difference of time-frequency graph between single target and multiple targets. The residual network can then output an estimate of the number of radar targets. Simulation results show that this method can estimate the number of radar targets effectively.

Abstract:The obtuse dihedral structure plays an important role in the stealth characteristics of the target, but its bistatic characteristics are still unclear. The method of combining electromagnetic simulation and statistical modeling is utilized to analyze its bistatic scattering characteristics from the perspective of frequency domain, space domain, polarization domain and statistical distribution. Studies have shown that when the electrical size is small, the bistatic scattering enhancement characteristics are not obvious, and the probability density distributions of monostatic/bistatic Radar Cross Section(RCS) are very different; the bistatic RCS probability density distribution of co-polarization exhibits bimodal characteristics. For this reason, the Bimodal Lognormal Distribution Model(BLDM) is proposed. This distribution model has achieved an ideal fitting effect. When the electrical size is large, the co-polarized bistatic forward scattering characteristics are significantly enhanced, and the monostatic/bistatic RCS probability density distributions are similar, which conforms to the lognormal distribution and the chi-square distribution. The law revealed has reference significance for the utilization and detection of obtuse dihedral structures.

Abstract:As the typical signal of Aegis radar, the intra-pulse multi-carrier frequency signal has awesome advantages of anti-interception and anti-jamming. However, its signal processing method is unclear. Taking the intra-pulse four-carrier frequency signal as an example, its signal characteristics and processing methods are studied. Based on the principle of optimal detection probability, the possible processing methods are proposed, and the processing framework and process are given. Especially for the case of aiming interference, the interference detection algorithm is employed to eliminate the interfered sub pulses. The detection performance of the two processing methods in different scenarios is compared through signal level simulation. The conclusion provides a reference for the processing and application of intra-pulse multi-carrier frequency signal.

Abstract:Multi-expert evaluation, as a traditional and effective method to evaluate the anti-jamming capability of radar systems, has the disadvantages of inaccurate evaluation caused by differences of expert levels and individual preferences. In this paper, by combining Analytic Hierarchy Process(AHP) with Principal Component Analysis(PCA), an AHP-PCA method is proposed to ensure the consistency of multi-expert group decision-making. The comprehensive results about the anti-jamming capability of the seeker system in the same environment are obtained through the application of AHP-PCA to the anti-jamming capability evaluation of radar seekers. Then the consistency of the group decision on the comprehensive evaluation results is described quantitatively. The evidences suggest that the AHP-PCA method can reduce the impact of evaluation inaccuracy and the subjectivity of evaluation caused by different preferences of experts, and that AHP-PCA is of engineering application value.

Abstract:Due to the relatively good penetration, low energy and broadband properties, terahertz waves have considerable application prospects in the fields of high-speed space communications, environmental monitoring, heterodyne detection, medical detection, non-destructive testing, and national defense security. As one of the core component of terahertz active and passive devices, terahertz waveguide is an indispensable part of the terahertz application system. The performance of the waveguide structure and functional devices determines the signal transmission efficiency of the terahertz system. The integrated terahertz waveguide has an important influence on the volume of the terahertz device. In recent years the development of terahertz waveguides has made great progress, from ordinary metal hollow waveguides to metal wire waveguides, dielectric optical fibers, and then to the recent artificial surface plasmon waveguides, graphene, lithium niobate and other new waveguides. These waveguide techniques demonstrate respective and exciting advantages. This review comprehensively introduces the latest developments in the field of terahertz waveguides, and prospects for its future applications.

Abstract:Target tracking is an important technology in aerospace Telemetry Track and Command(TTC) scope. An algorithm for target tracking in mobile multi-beam TTC system is proposed. In this algorithm, the application model and the processing steps are given for mobile multi-beam TTC system. In the simulation experiment, several typical scenes are constructed and the precision of target predicting is also analyzed. Finally, several constructive conclusions are made for practical engineering applications.

Abstract:A method on inhomogeneous sensors coordination direction and cueing is studied for multi-sensor management in C⁴ISR systems. Firstly, direction and cueing models are derived from azimuth and pitch. Then, direction and cueing areas are discussed based on passive sensor effect range. The direction and cueing errors models are built based on measurement errors and position errors. The direction and cueing probability are computed at last. The simulation results validate the correctness and feasibility of proposed model.

Abstract:A sixth order Ka band filter is presented based on the method of space mapping of single port group delay simulation. The filter is fabricated on aluminum oxide ceramic substrate, and the chip size occupies 8 mm×2.5 mm×0.254 mm. The measurement results show that the center frequency of Ka-band filter is located at 30.68 GHz with 3-dB Fractional BandWidth(FBW) of 11.5%, and the minimum insertion loss within the passband is about 1.75 dB.

Abstract:Based on the actual terrain and meteorological conditions, a method of extracting high-precision elevation data on an arbitrary terrain path from a three-dimensional digital earth is achieved by interpolation, and combining with atmospheric refractive index model and parabolic equation model, the propagation loss of electromagnetic waves in any terrain profile is calculated. The energy coverage of a monostatic radar at a certain altitude of space is computed. The simulation results show that the method proposed in this paper can deal with effects on radar energy coverage caused by both meteorological and georaphical factors, and better exemplifies the propagation effects of electromagnetic waves while comparing with human visual range. It provides a reliable technical approach for predicting radar energy coverage in complex meteorological and geographic environments effectively.

Abstract:In order to improve the magnetic focusing performance of coil and expand the application of coil function, the 8-shaped coil is improved. And the main variable parameters of the coil are optimized through a hybrid optimization algorithm. And 8-shaped coils with different sizes are obtained. The coil simulation model is established, and the focusing and functional effects of the optimized 8-shaped coil are analyzed through optimization simulation. An experimental model consistent to the simulation model is built, and the simulation results are verified by using a uniform steel plate with 1 m of length,1 m of width, and 5 mm of thickness and a solid conduit. The effectiveness of theoretical simulation is proved through comparison function. The improved 8-shaped coil model with different sizes can realize multi-function application. Under certain focusing, the coil can be flexibly applied to Helmholtz coil, Transcranial Magnetic Stimulation(TMS) coil array model and Functional Magnetic Stimulation(FMS) coil array.

Abstract:Multipath routing is essential to overcome the high loss rate in Wireless Sensor Networks(WSNs). Current proposals rely on centralized computation or iterative distributed algorithms and consume large amount of convergence time. Therefore, Exploration Packet-based Multipath Routing(EPMR) is proposed in this paper. EPMR routing first collects local topology information by using the transmission of exploration packets. According to the arrival time of the received exploration packet, the port priority is set, and the node that gives priority to the port priority participates in the route. Once participating in a path, the node will no longer participate in other paths between the source node and the destination node pair, thus ensuring the disjunction between multiple paths. Simulation results show that the proposed EPMR improves the packet transmission success rate and cuts the running time.