A two-way terahertz beam steering device is designed and proposed based on phase change material vanadium dioxide(VO2) and coding metasurface technology. At 0.7 THz, by giving the device thermal excitation to control the phase transition state of VO2, the device can be switched between two working modes of reflection and transmission. When the device temperature is higher than 68 ℃(the phase change temperature of VO2), the VO2 turns into metallic state, and the device works in reflection mode which means the device efficiently reflect and split the incident wave into several beams with similar energy and different directions. Under normal temperature, VO2 is in insulating state, and the device works in transmission mode to transmit terahertz wave efficiently. The dynamic control of beams in both directions of reflection and transmission makes the device itself no longer an obstacle to transmission of reflected or transmitted waves. This dynamic two-way control of the terahertz beam is very useful in terahertz wireless communication scenarios.

The enhancement effect and mechanism of the micro-nano composite structure composed of micro-pyramid array and nano-scale alumina(Al2O3) film on the modulation performance of silicon-based optically controlled terahertz modulators is studied. Experiments show that the micro pyramid array on the silicon surface can significantly reduce laser reflectivity compared with semiconductor silicon wafers, improve laser utilization, and increase the area of terahertz control. More importantly, the nano-thickness Al2O3 film deposited on the pyramid array can further reduce the laser reflectivity and significantly improve the modulation effect of the terahertz wave. Under the laser power density of 95.5 mW/mm2, its modulation depth can reach up to 91.2%. The optically controlled terahertz modulator has high modulation depth at low laser power, and shows a huge application potential in the field of terahertz imaging and communication.

The terahertz wave frequency band is located between microwave and infrared. Because the electromagnetic wave in the terahertz band is at a lower energy level, it has better resolution on the intramolecular force (intramolecular hydrogen bond, etc.), molecular interaction and actions of organic molecules like vibration and rotation. Carbohydrates are typical organic molecules, in which glucose (C6H12O6) has many isomers whose uses are differently. In this paper, the terahertz time-domain spectroscopy technique is utilized to measure four kinds of isomers of sugars in the range of 0.1-2.0 THz, and the absorption spectrums of the measured substance in solid state are obtained under ideal thickness. The differences in the spectrums are explained from the perspective of molecular space structure and intramolecular hydrogen bonding; the phenomenon is predicted that the absorption intensity and the absorption frequency point position of each solution may change with the concentration of the solution. The correctness of the prediction is confirmed by the obtained absorption spectra. It is also discovered that the absorption spectra of solid saccharide and its aqueous solution are strongly correlated.

Propagation of terahertz wave in sand and dust environment is investigated in this paper. The effects of sand and dust are included to the atmospherical attenuation based on the International Telecommunication Union(ITU) standard. The atmospherical attenuation is calculated by using the atmospheric Millimeter-wave Propagation Model(MPM). The attenuation due to sand and dust is calculated according to the Mie’s theory. The total attenuation is predicted by summing up the atmospherical attenuation and the particle attenuation. The calculation results can provide reference for terahertz applications in sand and dust environment, as well as other particulate environments for assessment of terahertz wave propagation.

The theory and simulation of the 0.5 THz waveguide dual-directional coupler is introduced. By using scheme of double rows, equal spacing, different diameters of multiple holes, the 0.325- 0.5 THz broadband waveguide dual-directional coupler is realized, and the simulation and test curves are given. It indicates that, the coupling factor is 7.6 dB±1 dB, the directivity is greater than 18 dB, and the return loss of the input port is greater than 16 dB. The coupler has excellent performance and has been applied to S-parameter test system.

A passive terahertz imaging system with high resolution and long distance is designed by using the terahertz wave imaging method. The system consists of a scanning module, terahertz detectors and quasi-optics. The system has the operating frequency of 110 GHz, the object distance of 6.0 m, and the detector field of 2.0 m×0.8 m. The resolution of the system is 2.5 cm. It is simulated and verified by experiments in GRASP. This system can check the articles carried with human body at a no-touch and non-stop way.

A fast recognition method of Reed-Solomon(RS) code based on check-sum is proposed to reduce the computation and improve the recognition speed. Firstly, the cyclic code with the primitive element of each possible finite field as the unique code root is constructed. The check-sum is calculated by using the binary check matrix of the cyclic code and is compared with the threshold so as to recognize the coding field. Then, the cyclic code with each element of the coding field as the unique code root is constructed. And the check-sum corresponding to each element is calculated. Finally, the generator polynomial is recognized based on the continuity of RS code roots. Compared with the spectral cumulant method, the proposed method improves the recognition speed by about one order of magnitude and the recognition performance by 0.1 dB; while at the error rate of 0.001, the amount of data required to achieve the same recognition performance is about 1/3 of the original method. Simulation results show that the proposed method is much better than the spectral cumulant method in terms of recognition speed and data requirement.

Automatic Dependent Surveillance-Broadcast(ADS-B) signal receiver technology is studied for the design requirements of low-cost, high-performance ADS-B system. The ADS-B signal software receiver based on 1090ES mode is designed based on software radio technology. The design is verified with RTL-Software Defined Radio(SDR) and Matlab, realizing the actual reception of ADS-B signal for civil aviation flights. Compared with the traditional ADS-B receiver, it has the advantages of simple structure, high flexibility and high development efficiency.

A Multiple Input Multiple Output(MIMO) optical wireless communication technology based on Discrete Multi-Tone/Quadrature Amplitude Modulation(DMT/QAM) and Space-Time Block Coding (STBC) is proposed in order to solve the problem of indoor diffuse optical wireless communication. Firstly, the channel model of indoor infrared wireless links is established based on DMT/QAM technique by considering the impulse response and noise characteristics of indoor all-optical wireless channel. Then, based on STBC technology, an MIMO wireless communication system for indoor diffuse optical wireless communication is proposed, and the important performance indicators, namely Signal-to-Noise Ratio(SNR) and Bit Error Rate(BER), at the receiver are obtained by analysis. The experimental results show that the proposed indoor MIMO optical wireless communication technology can not only reduce the BER for the system, but also obtain a better SNR compared with other traditional schemes, thus reducing the required optical transmitting power.

In the design of the speed dragging deception jamming system, it is necessary to quickly generate the interference signals and modify the interference parameters to deal with the complex and varied electromagnetic environment. The accuracy and stability of the frequency of the interference signal, as well as the generation speed of the interference signal directly affect the effect of the interference. The basic principles of deception jamming and Direct Digital Synthesizer(DDS) are introduced, the implementation of Field Programmable Gate Arrays(FPGA) based on System Generator and DDS for multi-speed deception jamming is presented. The construction of interference module is proposed and its verification methods are put forward. The test result proves that the DDS technology is very suitable for the synthesis of the interference frequency; and System Generator is very suitable for the FPGA implementation of multi-speed dragging deception jamming.

Electromagnetic situational analysis is a crucial task in information warfare, and modulation signal recognition by using Deep Learning(DL) is one of the key technologies. In this paper, the modulation signals are firstly transformed into the form of constellation diagrams with color information, and two Convolutional Neural Networks(CNNs), VGG16 and AlexNet, are selected to complete the modulation signal recognition task by using DL. The results show that a recognition accuracy higher than 99% can be achieved when the Signal-to-Noise Ratio(SNR) of noise is greater than or equal to 0 dB. Since the computational performance and storage performance of military devices are more stringent in controlling, the Average Percentage of Zeroes(APoZ) method is adopted to compress the DL model. The results show that with 0 dB SNR, AlexNet can be compressed by 3 466 times and VGG16 can be compressed by 20 156 times for model parametric quantities, and by 2 314 times and 13 475 times for floating-point operations, respectively, without losing recognition accuracy. In summary, the proposed method is both feasible and efficient in modulation signal recognition.

A new solution is proposed to integrate Free-Space Optics(FSO) technology into the existing RF-based Wireless Mesh Networks(WMNs) in order to improve the capacity of wireless mesh networks. Firstly, based on the expected long-term uplink and downlink traffic demands at each node, an Integer Linear Program(ILP) is constructed for the joint assignment of FSO transceiver and RF link scheduling to find the key location nodes which increase the overall network capacity to the greatest extent if they get upgraded. Secondly, in order to avoid the complexity of the original ILP, a Probabilistic Greedy Scheduling(PGS) algorithm is proposed, which can calculate a feasible solution at a very low computational cost. As a comparative benchmark, a Simulated Annealing(SA) algorithm is also proposed. The simulation results show that the network capacity can be improved by upgrading some key location nodes.

A kind of high integrated multifunctional sum-difference network which works in the millimeter wave band is presented. In the sum-difference network, a passive sum-difference network, dividers, active receivers, active transmitters, RF switches and a control circuit are integrated. Compared with the conventional RF sum-difference network, this highly integrated design proves to have much less volume and weight. As shown in the experiment measurement, the ports are well matched, and good RF performances are observed within highly reduced design.

High-power microwave source is widely used in the application and effect research of high-power microwave. As the input of test conditions, its control and measurement operations need to be convenient, reliable, clear and recordable. The integrated technology of measurement and control for S-band 1 MW high work ratio microwave source is studied. The remote control is carried out by optical fiber communication. The output signal and test signal are monitored by digitizer instead of oscilloscope. A two-stage amplifiers link is adopted through solid state amplifier pushing klystron amplifier. The output characteristics are measured and the effect of conditioning parameters on the output signal is studied. The integration of measurement-control can monitor the output of microwave source in real time, which is helpful to the experiments of microwave application.

Taking planar phased array antenna as the research object, the calculation method of the beam-control code is described in detail on the basis of the function model of the front antenna pattern. The architecture of the beam-steering system is analyzed. The calculation method of beam controlling code is put forward by combining lookup table method with distributed computing. The software processing flow is expounded, and the technical advantages of this method are compared with the traditional methods. The simulation analysis of the antenna pattern shows that the method can control beam pointing and realize one-dimensional scanning and two-dimensional scanning, one-way scanning and omnidirectional scanning with good accuracy. This work has important guiding significance for the design of the beam controlling system, and can be extended to other array antenna models.

The integration of radar T/R modules has become higher due to the rapid development of integrated circuits, and multi-channel tile type T/R modules that are integrated with antennas have emerged. Due to the integration of the antenna, the original component test method is no longer applicable to the transceiver of the new structure. An auxiliary radiation contrast test method is proposed, which uses the radiation method to test the component antenna unit firstly, then tests the components of the integrated antenna, and finally deducts the influence of the antenna on the component circuit performance, and obtains the performance parameters of the component circuit. Based on the analysis and testing principle, a multi-channel X-band tile T/R component with integrated antenna is utilized to test the transmit power, receive gain and phase consistency. The test results are compared with that of direct test of the circuit. The amplitude error is <0.63 dB and the phase error is <10.5°, which meets the engineering application requirements.

A wideband antenna which has a structure of an equilateral triangular slot ring with a pair of branch slots is proposed. Based on the principle of multi-mode resonance, the antenna feed is set in the non-symmetrical position of the triangular slot ring, and the two branch slots are added symmetrically to the triangular slot ring in order to form many resonance circuits. Therefore, multi-mode resonance is obtained and the bandwidth of the antenna is improved. The results of simulation and measurement are basically consistent. The measured impedance bandwidth of the antenna is 2.11-3.32 GHz, |S11|<-10 dB, and the relative bandwidth reaches 44.5%. Within the impedance bandwidth, the antenna radiation performance is good, and the direction pattern is basically the same. The antenna can be applied in LTE 40 and 41 wireless communication systems, and the triangular slot ring structure can provide some reference for the research of wideband slot microstrip antenna.

Aiming at the synthesis of space sparse arrays with constraints on array aperture, array spacing and number of arrays, a Lévy flight Particle Swarm Optimization(PSO) is proposed. The Lévy flight PSO is introduced to increase the particle position of the population, avoiding the algorithm falling into the local optima and renewing unsolvable. Simulation results show that the Lévy flight PSO has better convergence accuracy than the genetic algorithm and PSO in the literatures, which verifies the effectiveness and robustness of the proposed algorithm.

A new microwave band-stop filter based on two-dimensional photonic crystal is proposed in order to improve the transmission quality of the wireless communication system. The filter consists of a line defect waveguide and Aubry-Andr-Harper(AAH) resonator. By changing the distance between the AAH resonator and the main waveguide, the coupling coefficient between them is increased, and the filtering of the microwave band at 1 668.3 μm is achieved. Based on the Finite Difference Time-Domain(FDTD) principle, simulation is performed in Lumerical platform. The results show that the filter has excellent performance: the center wavelength of the stop band is 1 668.3 μm, the stop band attenuation is 25.2 dB, the pass band insertion loss is 0.2 dB, and the quality factor Q value is 1.5×104. The device is of small size and simple structure, and it is easy to be integrated on a large scale. It has important application prospects for Ultra Wideband(UWB) communication.

Pattern recognition of hand movements based on surface electromyography(sEMG) signals has been widely studied and has good classification performance in healthy subjects. However, for the daily use of amputees, its performance needs to be further studied. In this paper, the electromyography signals of amputees are collected for 10 days to investigate the classification performance of different movements. The practical application conditions are simulated, the time-domain features are taken as the input of Support Vector Machine(SVM), and hand movements recognition is performed on both sides of the arm. As a result, the classification performance of the healthy side is much better than that of the amputation side, because the amputation reduces the stability of the movements. At the same time, different time-domain features are adopted to classify the movements. The results show that the newly proposed feature has better classification performance. The results of classification of different movements show that amputees can control basic hand movements through electromyography signals, but the performance of fine movements needs to be further improved.

The classification and recognition theories of the same type of equipment based on the Radio Frequency Fingerprint(RFF) of the communication radiation source are studied. The integral bispectrum values of the communication signal are extracted as the feature vector of the device, and the Support Vector Machine(SVM) classifier is used for identification. After constructing a radiation source identification system, the measured signals are used for simulation testing. The simulation results show a stable recognition effect by using the proposed method, and the system can achieve nearly 90% classification recognition accuracy when the Signal to Noise Ratio(SNR) is -22 dB. This result validates the effectiveness of bispectrum-based RF fingerprint extraction method.

A mobile data collection scheme based on compressive sensing is proposed in order to reduce the energy consumption and ensure real-time performance of data collection in UnderwaterWireless Sensor Network(UWSN). Firstly, based on the Distributed Energy-Balanced Unequal Clustering (DEBUC) protocol and compressive sensing theory, cluster nodes decide whether to participate in compressive sampling according to the designed sparse measurement matrix, and transfer the obtained measurement results to the cluster head. Then, the data at cluster head is mobile collected by Autonomous Underwater Vehicle(AUV) to the data center. This problem is modeled as a Traveling SalesmanProblem(TSP) based on the maximization of information quality, and an approximate algorithm is proposed to solve this problem. The simulation results show that, compared with the existing underwater data collection algorithms, the proposed scheme effectively reduces the data collection delay and prolongs the lifetime of network, with assuring the reliability of data collection.

The function of pheromone in image edge detection algorithm based on ant colony optimization is not obvious and it is difficult to obtain the global optimal solution, thus reducing the accuracy and efficiency of the target edge detection. An Ant Colony Optimization(ACO) based on Bacterial Chemotaxis(BC) is proposed to improve the performance of edge detection. Firstly, the best solution is found through bacterial chemotaxis to produce the initial value of pheromone. Then, the initial value of pheromone obtained from BC is used as the initial pheromone of ACO, to calculate the walking probability of each ant and choose the walking path. When ants experience a pixel, local pheromones are updated. After all the ants complete the iteration, they update the global pheromone and search for the global optimal solution. Finally, according to the relationship between the optimal solution of pheromone and the threshold, the edge and non-edge are obtained. The results show that the proposed method has a great improvement in search accuracy, optimization speed and stability. Compared with other edge detection algorithms, it has better edge continuity, clarity and detection accuracy for small edges with perfect convergence speed.

The current image fusion methods mainly use image energy features to fuse layer content, and ignore the significant information of image, resulting in low contrast in the fusion image. In this paper, a method is proposed, which will fuse visible and infrared images based on the significant information of image. Firstly, a smooth transform is designed to decompose the visible and infrared images by using the L0 and L1 norms, and obtain the base layer and detail layer images with good edge features. Then, by using the frequency tuning method, the significant information in the infrared image is obtained to establish the fusion model of the base layer image, and get the fusion base layer image. Through the information entropy features of image, the fusion model of detail level image is constructed, and the fusion detail level image is obtained from the information relevance of different detail level images. The fusion image is obtained by summing the fusion detail layer image and the fusion base layer image. Experimental results show that this algorithm can better fuse visible and infrared images than current algorithms; its fusion results can not only highlight the target information, but also have better contrast.

Urban land use classification is of great significance for capturing current situation of cities accurately and optimizing urban spatial structure. An urban land use classification model specifically for China is proposed by using remote sensing images. Firstly, a multi-resolution feature fusion convolution neural network is designed to recognize urban land use types. Besides, according to the distribution characteristics of urban functional areas in China, a new dataset for the urban land use classification is proposed. Experimental results show that the proposed work can reach 88% accuracy on six urban land use types, which validates the effectiveness of the algorithm in the classification of urban land use. Finally, a case study for part of Beijing’s main urban districts demonstrates the value and effectiveness of the proposed model for providing data support in the field of urban planning.

In the Permanent Magnet Synchronous Motor(PMSM) speed control system, an improved active disturbance rejection control strategy with higher tracking accuracy for time-varying input is proposed. The traditional active disturbance rejection controller is mainly used for fast and static-free tracking of step signals, but there is a large tracking error for time-varying signals, which limits the application of active disturbance rejection controller. In this paper, the theoretical analysis of the existence of steady-state error is carried out, and then an improved speed Active Disturbance Rejection Controller(ADRC) with derivative feedforward and Parallel Linear Extended State Observer(P-LESO) is designed to reduce the tracking error of the system. In order to observe and compensate the reverse electromotive force in real time and reduce the current following error, a current loop linear active disturbance rejection controller is designed. By constructing Simulink simulation model for verification, the control system not only improves the tracking accuracy of PMSM for time-varying input, but also has a good dynamic performance for step input.

The work of Wireless Sensor Networks(WSNs) depends on reliable coverage of the area to be monitored. The problem of coverage holes arises when one or more nodes fail due to energy depletion or harsh physical environments. Therefore, Fuzzy Inference Systems(FIS)-repair node Selected(FISS) algorithm is proposed in this paper. FISS algorithm adaptively adjusts the sensing radius of node, and covers hole by moving nodes. The residual energy and coverage overlap rate of the nodes are taken as the input of FIS, and the output of FIS is to be the weight of the repair node. The node with the maximum weight is selected as the repair node. At the same time, according to the network conditions of the repair nodes, the movement direction and distance of the repair nodes are estimated. Finally, the repair of the covered void area is finally realized. Simulation results show that the proposed approach outperforms others in terms of coverage and energy consumption.

Aiming at the problems of the resource limitation of nodes and the error-prone communication chain in Wireless Sensor Networks(WSN), a secure and efficient remote authentication protocol based on WSN is presented. It adopts the centralized cluster-based hierarchical WSN to select the cluster head with the optimal percentage, and the cluster head is authorized to communicate with neighboring nodes; the network load balance is realized by minimizing the energy consumption of the nodes. Then each cluster head acts as a server, ensuring data authentication and exchange with each payload that delivers the message, and authenticating nearby nodes to form clusters. Simulation results indicate that the presented protocol is better than the existing protocols of improved Low Energy Adaptive Clustering Hierarchy(imp-LEACH) and secure LEACH(sec-LEACH) in the aspects of security, robustness, handshake duration, average energy consumption, and average network throughput.

Aiming at the problem that the existing deep collaborative attention models in the Visual Question Answering(VQA) task only consider the unidirectional attention of the question-guided image, which leads to the lack of interactivity of multimodal learning, a multimodal bidirectional guided attention network is proposed. The network consists of multimodal feature extraction module, bidirectional guided attention module, feature fusion module and classifier. The extracted image and question features are respectively output with weighted attention features after passing through layers of attention, and then the features are linearly merged into the softmax classifier to obtain the predicted answer to the question. Finally, the counting module is combined to improve the counting ability of the model. The results show that the model performs well on the public data set VQA v2.0, and obtains an overall classification accuracy of 70.77% and 71.28% on the test_dev and test_std, respectively, showing certain advantages compared with most advanced models.

Radiation effects and radiation mechanism of Micro Electromechanical Systems(MEMS) accelerator are summarized, which indicates the importance of MEMS radiation effect and hardening techniques study. The radiation sensitivities of different types of MEMS accelerator are introduced, as well as the degradation mechanism of radiation effects, radiation damage of different materials and Si radiation effect. The international radiation experiments about MEMS accelerator are emphatically analyzed, and the trends of radiation hardness of MEMS accelerator are put forward.

Ion source injected Interdigital H(IH) mode Linac has great potential to accelerate high current particle beam with high efficiency and low power consumption. One prototype of this accelerator was developed by Institute of Fluid Physics, China Academy of Engineering Physics. This accelerator was designed to accelerate protons from 0.04 MeV to 2.0 MeV with an IH cavity. The accelerator now has been constructed and tested. Beam test results show that the transmission is about 32.77%, and all parameters are consistent with the designed values, which proves the effectiveness and feasibility of this kind of accelerator.

The magnetic switch is important for solid-state high power pulse modulators due to its excellent characteristics, such as long lifetime, high stability and high power capacity. Some applications require the synchronization of multiple pulse generators, for example, to obtain higher load power. Magnetic coupling is a simple, passive, maintenance-free technique, which can be utilized to reduce the output timing variations of magnetic switched pulse generators. In this paper, a synchronization experiment of two magnetic switches is carried out. The experimental results show that the time difference between the two pulses is reduced from 2.2 μs and 0.6 μs to 0.3 μs and 0.1 μs respectively after coupling the magnetic switches, which demonstrate that the magnetic coupling technique can make magnetic switches operate synchronously. An improved circuit model based on the gyrator-capacitor approach is established which can effectively simulate the synchronization process of magnetic switches. Analysis about the synchronization mechanism is also given.

As an important second-generation semiconductor material, indium phosphide has wide bandgap, fast electron drift and better radiation resistance than Si and GaAs. It can be used as an alternative material for the preparation of electrical devices on space vehicles. With the nano-size of semiconductor devices, the displacement damage caused by low-energy proton irradiation in space environment is one of the main factors affecting the electrical properties of components. In this paper, the types and proportions of Primary Knock-on Atom(PKA) produced by low energy protons irradiation and the depth distribution of Non-Ionizing Energy Loss(NIEL) of protons with different energies are obtained by Geant4 simulation. The results show that the probability of proton capture and nuclear reaction increases with the increase of proton energy, which decreases the proportion of recoil atoms In and P and enhances other recoil atoms in elastic collision. The NIEL peak tends to move forward in depth of the bulk material with the increase of proton energy, which means the area of serious displacement damage gradually shifts from the end of the material to the surface of the material.