Abstract:

Rydberg atoms can be used for high-precision, self-calibrating measurements of microwave and terahertz fields due to their large polarizability and electric dipole moments and high sensitivity to external electric fields. In this paper, the research progress of using the Electromagnetically Induced Transparency(EIT) effect and the Autler-Townes(AT) splitting of Rydberg atoms to achieve high-precision detection of microwave and terahertz fields, is reviewed, as well as the research of Rydberg atoms in fast terahertz imaging.

Abstract:

Aiming at the requirements of millimeter and sub millimeter wave radiometer for quasi optical feed network, a 23~425 GHz ten channels quasi optical feed network is designed by GRASP software, using flat plane to achieve a double layers quasi optical feed network and reduce the size,using polarization grids and Frequency Selective Surfaces(FSS) to separate different channels. Through simulating the specifications of each channel, the test results are consistent with the simulation results.

Abstract:

In this paper, a different network architecture is proposed for intelligent segmentation of THz security inspection images based on Generative Adversarial Network(GAN) and multi-head attention mechanism. The algorithm is prone to address the problems of low-resolution THz images, blurred edges of dangerous goods, and inability to segment dangerous goods efficiently. More realistic images are obtained by studying the feature map of the deep discriminator. The multi-head attention mechanism is introduced to improve the recognition ability of the model to the characteristics of dangerous goods. A large number of experimental results of segmentation of terahertz security inspection images show that the proposed GAN has better generalization ability at the same depth than the traditional Convolution Neural Networks(CNN).The introduction of multi-head attention mechanism strengthens the model's learning of the characteristics of dangerous goods, which also has a good effect in the case of unknown dangerous goods category. The Intersection Over Union(IOU) index is 9.6% higher than that of RestNet-50, 21.3% higher than that of RestNet-18, and 12.3% higher than that of U-Net. The research is conducive to image segmentation algorithms for more accurate and efficient processing of THz security images, which broadens further applications of THz intelligent security systems.

Abstract:

Terahertz Time Domain Spectroscopy(THz-TDS) is employed to detect the Zinc Citrate(ZC) dihydrate and its dehydration kinetics. Results show that there are two prominent absorption peaks:one at 1.91 THz, the other at 1.77 THz for the ZC dihydrate, while there is no featuring absorption peak for ZC anhydrate at room temperature. When the temperature increases, the absorption peak of ZC dihydrate at 1.91 THz decreases and gradually disappears. According to the variation of the absorption peak area of ZC dihydrate at 1.91 THz under different temperatures and heating time, the enthalpy change of ZC dihydrate transforming to anhydrate is 381.13 J/g(232.6 kJ/mol) by using the Arrhenius equation, and the error is 4.2% compared with the traditional Differential Scanning Calorimetry(DSC) measurement. These results indicate that THz-TDS can be used as an efficient and fast technique for the detection of ZC dihydrate and its dehydration kinetics.

Abstract:

To design the optimal protection scheme for cultural relics of different materials and production techniques, the cultural heritage scientists are in constant search of the most effective nondestructive testing method for the overall survey of the cultural relics. Due to the unique properties of terahertz wave's low energy, strong penetrability for non-metallic and nonpolar substances, simultaneous measurement of amplitude and phase information, strong anti-interference capacity, etc., terahertz technology has been gaining an edge over other conventional nondestructive testing methods. In this review paper, the latest progress of terahertz technology applied in nondestructive testing of cultural relics are introduced, and the terahertz spectra characteristics of various cultural relics materials are illustrated. The principle and characteristics of terahertz imaging detection technology are expounded. The key issues in the application of terahertz nondestructive testing technology for various cultural relics are discussed, and the most successful and representative application examples of terahertz technology in cultural relics science are listed. Finally, we present the developing trend of terahertz nondestructive testing technology in the field of cultural relics.

Abstract:

The traditional passive-resistance test of all electronic fuze adopts external on resistance test equipment or general on resistance test circuit design, which has nothing to do with the electrical performance test of full electronic fuze, and can not avoid the risk of the failure product burning after power on. Therefore, a systematic design idea is proposed to diagnose the electrical performance of passive-resistance and full electronic fuze. This paper designs a full-automatic test control architecture based on ARM chip and FPGA dual core architecture and a 24 bit high-precision four-wire passive-resistance test circuit. The passive-resistance of the external interface part of the all electronic fuze and the working characteristics of the fuze are comprehensively tested. The test results show that the design can be utilized to test the passive-resistance with high precision(the measuremetn accuracy is ±0.1%) as well as the comprehensive working performance after power on.

Abstract:

The multiple features are selected and classified based on Nonlinear Correlation Information Entropy(NCIE) for the target recognition problem of Synthetic Aperture Radar(SAR) image. The Gaussian mixture model is employed to model the probability distributions of different kinds of features and then the KL(Kullback-Leibler) divergence is utilized to evaluate the similarity among different kinds of features. The NCIE values of different combinations of features are calculated and the one with the maximum entropy is chosen as the optimal. The joint sparse representation model is employed to represent and classify the selected features. Experiments are conducted based on the MSTAR data under the standard operating condition and extended operating condition. The results show the effectiveness of the proposed method.

Abstract:

The emitter threat level evaluation is an important topic in electronic countermeasures. To deal with the disadvantages of the current methods for emitter threat level evaluation, the UTilites Additives DIScriminantes(UTADIS) method, which is a method of multicriteria classification, is introduced. It is indicated that UTADIS can produce reasonable and accurate evaluations of emitter threat level that reflect the preference of decision makers and can give more information of emitter threat degree. Thus, UTADIS has advantages in performance and applications and is a new way to effectively evaluate the emitter threat level.

Abstract:

This study investigates artificial noise aided Multiuser Multiple-Input Single-Output(MU-MISO) broadcast wiretap system designs in slow fading channel environment. We adopt a beamforming technique with artificial noise to achieve secure multiuser communication and optimize system performance. To overcome the complexity of this model, a novel optimization scheme using semi-closed-form expressions and Monte Carlo method is employed to derive the relationship between transmission parameters and secure transmission performance. In this article, we detail the procedure of our new method, and conduct some heuristic simulation works. The simulation results reveal how power allocation ratio and information rate influence the multiuser system secure transmission probability and effective secrecy throughput of the multiuser system. We compare the multiuser system security and throughput performance with each user's performance, which helps us to verify the security ability of our method. Our research results extend the traditional single-user artificial noise design method to multi-user scenarios, and provide ideas for solving the optimization problem of multi-user broadcast communication.

Abstract:

As a common structure of power electronic system, the unequal length multiconductor transmission lines model has a crosstalk problem which may affect the normal operation of the whole system. In this paper, the Finite Difference Time Domain(FDTD) format is employed to differentially discretize the transmission line equation, and the Kirchhoff’s law is utilized to process the connection positions of different multiconductor systems. Then, the iterative formulas of the voltage and current on the multiconductor transmission lines are derived, and the simultaneous solutions of all voltages and currents on the entire model are realized. Finally, the effectiveness of the method in analyzing the electromagnetic interference problem of electrically large transmission lines is verified by a numerical example.

Abstract:

It is one of the key technologies of underwater pulsed laser detection to suppress the backscattered noise caused by water transmission in signal processing. Based on the correlation between two adjacent detections of backscattering in the same water area, an improved Normal Least Mean Square(NLMS) adaptive filtering algorithm is proposed. The step factor is controlled according to the intensity of backscattering and the size of the filtered target signal to make it achieve good filtering effect for target signals at different distances and intensities. The algorithm is verified by simulation and swimming pool experiment. The results show that the filter algorithm can effectively filter the backscattered noise with a lower order for targets with different reflection strengths at different distances, and retain the target echo signal. Compared with the existing adaptive filtering method, it greatly reduces the computing resources required for filtering, and has certain application value in underwater pulsed laser detection systems.

Abstract:

Currently a number of image matching algorithms focus on measuring the distance between key points while ignoring the structure information of the images, hence are prone to mismatches. This paper presents an image matching algorithm using the geometric invariance of variance constraint coupling. With the help of Forstner operator, the interest value of pixels is calculated to detect the characteristics of the image. The gradient information of the image is calculated to obtain the direction value of the image. The circular neighborhood of image features is cut to obtain the fan-shaped sub domains. Based on the direction value of the image, the feature vector of the image feature is obtained by calculating the gray invariant moment in the fan-shaped sub domains. The region variance function is introduced to obtain the structure information of the image, which is added to the image feature matching process to constrain the results of Euclidean distance measurement and realize the image feature matching. Based on the geometric invariance between matching points, the matching image features are processed to get accurate image matching results. Experimental results show that compared with the existing matching techniques, this algorithm has higher matching accuracy, which up to 96.56%, 95.38% and 93.52% for non-transformed images, zoomed images and rotated images, respectively.

Abstract:

Aiming at the problem of low network coverage caused by uneven deployment and distribution of Wireless Sensor Network nodes, with the goal of maximizing wireless sensor network coverage, a network coverage optimization strategy based on Improved Firefly Algorithm(IFA) is proposed. This method uses the good point set method to initialize the population, improve the diversity of the population and lay the foundation for the global search. Simultaneously, it uses the sigmoid function with non-linear exponential decline as the inertia weight to balance the global and local search capabilities of the algorithm. Then, Gaussian disturbance strategy is employed to perturb individual position update and avoid the premature of the algorithm. The simulation results indicate that compared with Artificial Fish Swarm Algorithm(AFSA), seed Hybrid Particle Swarm Optimization(HSPSO) and Chaotic Glowworm Swarm Optimization(CGSO), this algorithm effectively enhance the network coverage rate and make the WSN more evenly distributed.

Abstract:

In order to improve the accuracy of image segmentation without changing the structure of original semantic segmentation models, an approach is proposed to train Semantic Segmentation models by using Generative Adversarial Network(SS-GAN). There are three steps related to this work: constructing the generative model of Fully Convolutional Network(FCN) structure to segment image preliminarily; constructing the adversarial model which can learn the high-order relationship between pixels and training it to improve the learning ability of generative model; adding the anti-loss to assist generative model training, encouraging generative network to learn the relationship between pixels independently. Experiments on Pattern Analysis, Statistical Modeling and Computational Learning (PASCAL VOC) and Cityscapes datasets show that the proposed method achieves better performance than the existing advanced methods, and improves Intersection over Union(IoU) by 1.56%/1.17% and 1.93%/1.55%, respectively.

Abstract:

Accurate and timely acquisition of the phenological information of winter wheat which is one of the main crops in China, is a prerequisite for its growth monitoring and yield estimation. Spaceborne Synthetic Aperture Radar(SAR) is an all-time and all-weather microwave remote sensing device, which can realize large-scale monitoring of periodic crop phenology. According to the time series Sentinel-1A SAR data, a phenological period identification method of winter wheat is proposed based on spaceborne dual-polarization SAR. This method uses eigenvalue decomposition and polarization scattering analysis to extract the backscattering coefficient, polarization entropy, scattering angle, etc., in different phenological stages to realize winter wheat phenology identification. The experimental results show that the overall accuracy of phenological phase identification reaches 79%. This method has practical value in winter wheat growth monitoring.

Abstract:

By using the 1 Pulse Per Second(1PPS) received from Global Positioning System(GPS), the disciplining method is studied for common secondary frequency source Temperature Compensated Crystal Oscillator(TCXO) and Coherent Population Trapping(CPT) atomic clock. A disciplining scheme of phase-locked loop is designed. The time difference between 1PPS from local frequency division and that received by GPS receiver is measured by Time-Digital Converter(TDC) to realize the locking of local signal to GPS time signal. TCXO has achieved frequency stability of 8.5 × 10 - 12 at 10 ks, and the average frequency accuracy at 35 ks after disciplining has been improved by more than 4 times. In addition, the noise model of CPT atomic clock is deeply studied and simulated through Matlab. The corresponding relationship between white frequency noise and random walk frequency noise on Allan variance curve is established. The results after disciplining by average filtering and Kalman filtering on CPT atomic clock are compared, and the frequency stability increases by an order of magnitude at 50 ks.

Abstract:

Effective choice of the solution is essential to achieve a real-time, bi-directional(full- duplex) communication of the smart grid. The Power Line Carrier(PLC) technology provides a low-cost solution, which suits China's own national conditions. In this paper, the advantages of OFDM PLC modulation technology are introduced. A PLC module of system model is established through the analysis of the input impedance under the low-voltage power line channel. The high-speed PLC module based on low-voltage Power Line is also designed according to the studies of power line channel. The results show that the design of the PLC module has featured high receiving sensitivity and anti-noise ability.

Abstract:

With the development of Internet applications, users’ demand for bandwidth is soaring sharply. Meanwhile，along with the development of broadband access technology, the endpoint can also adopt multiple network accesses. But due to one-way communication of traditional Transmission Control Protocol(TCP)，the waste of resources will exist. To this end，IETF has specifically proposed Multi-Path TCP(MPTCP) to implement TCP multiplexing，thereby enhancing the efficiency and robustness. This paper gives a review of the IETF’s research on MPTCP，including MPTCP architecture, routing and congestion control, aiming to provide a reference for deeply studying.

Abstract:

Traditional methods and instruments are not able to measure the true Root Mean Square(RMS) of distortion sine wave or non-sine signal accurately. This article introduces a method to measure the true RMS of any high frequency signal by using the true RMS measurement IC，AD536A，designed by AD corporation. The paper analyses the difference between the RMS measured by the average measure method and the true RMS in theory. It explains the disadvantages of current RMS measure method，and presents the design of true RMS measure circuit. The experiment results prove that the proposed method and circuit can measure the true RMS of any high frequency signal accurately.

Abstract:

The requirements for micro stress measurement of strain gauge are high precision，high linearity，high stability and high gain. One kind of differential amplifier circuit with excellent performance was designed. Some skillful techniques were adopted to avoid common voltage in the circuit and to reduce the temperature drift. The gain linearity is about 0.01%，and its Common-Mode Rejection Ratio(CMRR) is about 129 dB under work conditions.

Abstract:

Aiming at the problems in existing underground personnel positioning systems, an assisted positioning method based on pedestrian dead reckoning is proposed. Low-cost Inertial Measurement Unit(IMU) and magnetometer are employed to constitute a stable Attitude Heading Reference System (AHRS). The theory of inertial navigation is utilized, an algorithm for step detection is described, and Zero velocity Update(ZUPT) is adopted for velocity and position estimation to compose a pedestrian dead reckoning system. An experiment is performed in the corridor of a laboratory building to emulate the underground mine road environment. The experimental results demonstrate that the dead reckoning performs well and this method is an effective complement to existing underground positioning by improving the positioning accuracy.

Abstract:

Terahertz(THz) optoelectronics has promoted the development of the THz generation, transparent control, and detection methods，and hastened many devices in the past decades. Especially, THz metamaterials and metasurfaces will exhibit extraordinary electromagnetic response when the subwavelength scale metal structure is excited by the THz illumination. Therefore, they have been applied to the devices such as wave beam shaper, waveguide, and modulator etc. The THz metamaterials and metasurfaces also show the potential applications in the research fields such as sensors, communications, and radars. In this paper, the works about the spectrum and wavefront modulation with THz metadevices carried out in our group are summarized. The basic theory and corresponding experiment results for different devices are introduced. It is expected these works can pave the avenue of the application of the THz metadevices.

Abstract:

According to the requirements of safe, simple and nondestructive radiation effect investigation of semiconductor devices, the method of laser simulation was proposed and greatly promoted. Compared with large-scale facilities, laser simulation has various unique advantages. It helps understand the ionization radiation effect in depth and is an effective low-cost, table-top supplement for the hardness assurance. Its research shows great significance for radiation effect study in both theory and practice. In this paper, the basic principles of the interactions of γ and laser with semiconductor devices are firstly presented. Then the physical basics and characteristics of laser simulation are given, with the research progress review followed. The existing problems of current research are deeply discussed providing with feasible research approaches. In the end, necessary research contents in the future are proposed.

Abstract:

Ultra-wideband(UWB) communication shows its advantages of fast data transfer(100 Mb/s or above) in a relatively short distance(typically below 10 m) with relatively weak power consumption (energy spectrum below -41.3 dBm/MHz). Integrated with Multiple Input Multiple Output(MIMO) technology, channel capacity could be further enhanced. As a critical link in the ultrawideband communication，UWB antenna needs extra efforts in design optimization to boost the performance of the whole system. UWB antenna is defined as the antenna whose bandwidth exceeds 500 MHz or relative bandwidth greater than 20%. This paper takes the most representative Vivaldi antenna as a show case for multi-objective optimization design with statistical methods. The optimized miniaturized antenna(sized130 mm×100 mm) shows a -10 dB bandwidth of 2.4 GHz. The design method provides guidance in common wideband，multi-parameter antenna design.

Abstract:

Radio Frequency IDentification(RFID) series Radio Frequency(RF) card has been applied widely because of its stability，reliability and easy operation features. Aiming at multiple protocols，such as ISO14443 protocol，ISO15693 protocol and Tag-it protocol，this study proposed a new type of circuit design based on Advanced RISC Machine(ARM) for the RFID series RF card reader. The data stream encryption was implemented by using peripheral device in the operation. The system composition，working principle and work flow were introduced. Then，the detailed circuit design of the RF network and encryption hardware were presented，and the test and analysis for the design were performed. The results showed that the circuit could accurately read, write and encrypt various types of card within effective range.

Abstract:

The background requirements of the fuze antenna in terahertz spectrum as well as its advantages and disadvantages are introduced. The working principles and application characteristics of dielectric lens antenna in terahertz frequency are analyzed in order to implement the terahertz fuze antenna. The longitudinal size of H plane horn antenna can be reduced effectively by using fuze antenna formed by an H plane horn with dielectric lens antenna. The terahertz fuze antenna with different beam angles is achieved by focal technology of lens. The feasibility of the technology solution is verified through simulation.

Abstract:

High-speed data acquisition system is an important component in modern radar signal processing. A design of high-speed data acquisition system based on band-pass sampling was presented and applied to the signal processing of wideband receiver. The Virtex Series FPGA was used as the main platform to control the high-speed ADC08D1000 for completing data acquisition, transmission，storage and signal processing. High-speed First Input First Output(FIFOs) were selected as the storage devices to implement data rate conversion. The system realized the software and hardware design，and test results verified the feasibility of the solution.

Abstract:

This article introduces a new type of high speed，multi-modulated digital modulator with adjustable center frequency and bit rate features. It can realize the Quadrature Phase Shift Keying(QPSK) and 16QAM(Quadrature Amplitude Modulation) with 80 MHz center frequency and 7.936 5 MHz bandwidth. The general-purpose modulation arithmetic based on software radio，symbol mapping and the realization of pulse shaping filter are discussed. The measuring results demonstrate that the modulation scheme meets the requirements of practicability and general utilization.

Abstract:

The implementation of TCP/IP protocol stack on TM320DM642 platform could provide technological support for the application of multimedia embedded systems to networks. Both the function of TM320DM642 chip and the hierarchical structure of LWIP(Light Weight Internet Protocol) were analyzed. Network communications for TM320DM642 systems were implemented by the transplantation of LWIP, not by a solution scheme of NDK(Network Developer’s Kit). Testing examples verified the effectiveness of the LWIP transplanted method.

Abstract:

The Spatial Light Modulation(SLM) technology has been widely applied to the fields of threshold switch, high speed optical interconnection and optical logic operations, which demands good performance on the real-time and fast optical signal addressing. Compared with Electro-Addressing SLM(EA-SLM), Optically-Addressing SLM(OA-SLM) shows great advantages of fast speed and high resolution by parallel addressing. Nevertheless, how to achieve fast and stable optically addressing is the key point in practice. Based on ZnO thin film as a photoconductive layer, Liquid Crystal OASLM(LC-OASLM) is designed and fabricated; the modulation of the readout light intensity and phase distribution in the two-dimensional space is achieved effectively.

Abstract:

The design of code tracking loop is a key sector of the realization of noncoherent spectrum spread receiver. In order to realize the code tracking in noncoherent spectrum spread receiver, an energy-normalization digital delay-locked loop was designed, the structure of the loop and the calculating procedure of loop parameters were introduced. The characteristic of noncoherent spectrum spread was analyzed first，and then the key point of the loop design was pointed out. Based on this, the design and realization methods of code loop discriminator, loop filter, early and lag code generator were expatiated. A set of specific loop parameters were introduced as well. Modelsim simulation results and FPGA actual measured data prove the precise code tracking ability of the design.

Abstract:

The corresponding solutions are proposed to tackle with the disadvantages of conventional oilfield Geographic Information System(GIS), including inconvenience of Client/Server(C/S) mode operation and maintenance, being unable to perform real-time online Point of Interest(POI) rendering, being incapable of segmentation and location according to regions, etc. An oilfield information query system of Browser/Serve(B/S) framework based on AJAX+JSON+HTML5 is designed and implemented. Experimental results show that the POI real-time rendering and regional segmentation improve on their interactivities, and the experiences of users are enriched, which meets the actual requirements of oilfield development. This work has paved the way for the development of diversified network services.

Abstract:

A detector can achieve quick response when it is much smaller than the wavelength of the source signal in THz wave band at the expense of signal coupling capability．Therefore, an antenna is applied to collect signals in order to enhance the signal coupling capability of the detector．The properties of antenna determine the frequency response band，the sensitivity and other parameters of the detector directly. A planar-integrated antenna is adopted for signal acquisition in the Nb5N6 microbolometer detector, which is fabricated by lithography，lift-off and other processes of micro-fabrication. The Nb5N6 microbolometer is placed in the center of the planar antenna. Aiming for the center frequency of 0.32 THz, a special capacitive coupling design is proposed to improve the signal coupling capability．

Abstract:

The single-channel blind separation of GMSK(Gaussian Minimum Shift Keying) mixing signals is researched. The GMSK mixing signals can not be separated by the Per-Survivor Processing (PSP) algorithm directly, therefore, linear approximation processing of the GMSK signal is considered, which enables GMSK signal to be separated by the PSP algorithm. This algorithm separates the GMSK mixing signals by maximum likelihood estimation in the joint space of the symbol sequential and the channel parameters, reserves the best path and outputs the symbol pairs to get the separated signals. Simulation results show that the bit error rate performance produced by the PSP algorithm on separating the GMSK mixing signals is slightly better than that produced by the particle filtering algorithm; and the complexity of the proposed PSP algorithm is much smaller.

Abstract:

The application of CORDIC(COordinate Rotation DIgital Computing) arithmetic in solving transcendental function has become popular in modern engineering. A brief introduction of CORDIC arithmetic was given in this study. Taking the hyperbolic sine and cosine functions as examples, the method of realizing the arithmetic in FPGA was presented and simulated on ISE(Integrated Software Environment) platform. The result showed this arithmetic was of good precision and instantaneity because of using pipeline. This arithmetic has great practical value in some applications. In addition, a curve of the relationship between the iterative number and the error obtained by the Matlab simulation of the arithmetic can help designers planning the number of iterations for practical applications.

Abstract:

A double gate setting with priority of Doppler velocity and the Extended Kalman Filter(EKF) based Multiple Hypothesis Tracking(MHT) algorithm are proposed in order to realize Multiple Targets Tracking(MTT) in High Frequency(HF) ground-wave radar, and to effectively improve the performance of MTT by using the Doppler measurement. In the EKF based MHT, parameters obtained in the EKF are adopted directly to calculate the probability of each hypothesis. A simulation scene is built, and the EKF based MHT algorithm is compared with the one which assumes that the Doppler measurement is independent from the radius measurement. Simulation results show that the double gate setting helps induce number of clutter, and the EKF-based MHT algorithm is better than the other one under dense environments of HF ground-wave radar with stronger track-catching and false-alarm-filtering ability and higher efficiency.

Abstract:

A new usage of Hough Transform is introduced in this paper.Firstly,the position and scope of the license plate is located and the image that contains the license plate is picked up.Then, a two-stage Hough transform algorithm is applied to the image to cal

Abstract:

A forward secure strong proxy signature scheme is proposed on the basis of the proxy signature schemes and forward secure schemes.The security of the proposed scheme relies on the difficulty of solving discrete logarithm problems and the difficulty of com

Abstract:

Wavelet denoising is an important application of wavelet analysis in engineering.The keys of wavelet denoising,namely how to select threshold and how to utilize the threshold to dispose wavelet coefficients,are introduced.Via the noised simulated signal e

Abstract:

Based on three generally accepted basic hypotheses, the definition of environmental factor and restricting conditions of constant failure mechanism are discussed.The research status and common study methods of environmental factor are reviewed. Finally, a

Abstract:

For completing the scheme of hard target smart fuze, several factors influencing the outputting acceleration of the high-G accelerometer such as target material, impact angle, impact velocity, the fixed position of accelerometer, carry plane etc., are put