Abstract:

Terahertz(THz) imaging technology, as an emerging imaging method, has the advantages of being non-invasive, non-destructive, and high-resolution, and has achieved significant progress in recent years. This paper reviews and analyzes terahertz imaging technology from the perspectives of technical approaches and current research status. Based on the type of signal source, the technical characteristics of pulsed terahertz imaging and continuous-wave terahertz imaging mechanisms are compared and analyzed. On this basis, the paper focuses on the technical solutions with super-resolution and high-speed imaging capabilities, analyzes their current development status, and discusses their advantages in future terahertz imaging scenarios. Finally, the challenges of application-oriented terahertz imaging technology are summarized and prospected.

Abstract:

Interferometric imaging technology can accurately measure the tiny deformations or displacements on the surface of objects in a non-contact manner, demonstrating extensive application potential. In this paper, a reflection and transmission interferometric system based on the terahertz band is designed and constructed. This system directly reconstructs images using phase information after scanning. Experiments show that at frequencies of 164 GHz, 172 GHz, 196 GHz, and 204 GHz, the imaging quality and resolution of the Michelson interferometric system are superior to those of the direct measurement method. At 150 GHz, without using any imaging algorithm, the system can achieve half-wavelength resolution, with a contrast improvement of 50% compared to direct measurement. At 180 GHz, a Mach-Zehnder interferometric system is implemented, where the dual-path difference effectively reduces phase noise, thus proving the feasibility and advantages of the system. Terahertz interferometric technology provides a noncontact, high-resolution imaging solution for the imaging field.

Abstract:

A terahertz fourth harmonic mixer based on anti-parallel Schottky diode pair is introduced, and its Radio Frequency(RF) operating range covers 400 GHz to 600 GHz.The mixer use a multi-point ground structure at the RF ends, which effectively reduces the return loss of RF port compared to the traditional single point ground structure. By adopting an integrated RF-end design method, the number of matching branches is reduced by 30% during the design process compared to traditional methods, thereby enhancing design efficiency. The measured results show that the typical value of conversion loss is 20 dB and the optimal value is 14 dB in the whole working band when the Local Oscillator(LO) power is in the range of 7~13 dBm.

Abstract:

The quality of the insulation layer of high-voltage cables is crucial for the long-term reliability of power transmission and transformation systems. Non-uniformity in the thickness of the insulation layer can lead to localized tangential electric fields, which are prone to creating safety hazards. A reflective terahertz detection system, combined with a cylindrical coordinate scanning device, is employed to achieve full-angle scanning measurements of the insulation layer thickness of cross-linked polyethylene high-voltage cables. The non-roundness of the insulation layer thickness is quantified, and its distribution uniformity is assessed. The terahertz images intuitively display the interface wrinkle texture features of the insulation layer, which are highly consistent with the actual specimen morphology. This validates the effectiveness of terahertz imaging technology in the quality inspection of high-voltage cables, providing a new detection method and evaluation approach for the quality assessment of high-voltage cables.

Abstract:

Millimeter-wave holographic imaging systems based on phase imaging have been extensively applied in fields such as security screening and non-destructive testing, due to their special penetration capabilities and high-resolution advantages. While extending operational frequencies to higher bands for achieving better resolution, the problems of dense transceiver arrangements and high system complexity need to be considered. This study presents a W-band short-range high-resolution millimeter-wave holographic imaging system utilizing linear array scanning. By implementing a 25-transmitter and 100-receiver array configuration with integrated electronic circuitry design, the system achieves high-quality short-range imaging across the 85~105 GHz operational band. Experimental results demonstrate the system can obtain spatial resolutions superior to 2 mm in the horizontal direction and 2.5 mm in the vertical direction at an imaging distance of 0.5 m, confirming its enhanced performance in practical applications.

Abstract:

To meet the low electromagnetic scattering requirements of optical instrument windows, a metal microstructure model based on Voronoi diagrams is employed, arranging the metasurface structures in a checkerboard array. This design achieves effective reduction of Radar Cross-Section(RCS) while satisfying the transparency and imaging quality requirements of the instrument windows. Experiments shows that the checkerboard metasurface without transparentizing could achieve more than 10 dB RCS reduction in the frequency band of 11.6~17.9 GHz, and the phase response of the metasurface unit remains consistent before and after transparentizing. The designed transparent RCS-reducing metasurface has high light transmittance, can uniformly diffract stray light distribution, and possesses the characteristic of wideband RCS reduction. The research results provide a new idea for the design of low-RCS transparent windows.

Abstract:

With the development of Low-Earth Orbit(LEO) satellite systems, satellite-borne phased array antennas have been applied in satellite systems, providing the conditions for phased array measurement of the Direction of Arrival(DOA) of satellite-borne electromagnetic waves. In the current satellite direction-finding and positioning systems, the single-DOA positioning system is unable to locate aerial targets, and the dual-satellite Time Difference of Arrival(TDOA) and DOA joint positioning system requires synchronized measurement and calculation by two satellites with simultaneous visibility of the target to achieve positioning. To address these issues, a positioning method based on single-satellite dual-DOA is proposed. The principle and algorithm of single-satellite dual-DOA positioning are analyzed. Through simulation, the quantitative impact of different satellite intervals, direction-finding errors, and satellite position errors on the positioning accuracy of satellites is calculated. The Geometric Dilution of Precision(GDOP) of this positioning system is derived, and its feasibility is verified through simulation.

Abstract:

To address the issue of high computational load and long processing time in the imaging calculation process of lightning radiation sources using time-reversal algorithms in the frequency domain, a series of optimized acceleration methods for time-reversal algorithms are proposed. Firstly, the introduction of Graphics Processing Unit(GPU) parallel computing is further expanded to dual-GPU cluster computing, while adopting multi-threading concurrent programming methods of Central Processing Unit(CPU) and GPU to cover the time consumption caused by mutual waiting; secondly, the maximum energy search algorithm and phase difference filtering algorithm and other programs are written to the GPU to achieve parallel search and calculation of phase difference values; finally, the data acquisition and transmission module, GPU processing module, and positioning imaging module are integrated to achieve the integrated function from data collection to positioning imaging of lightning data. For a 500 ms segment of Very High Frequency(VHF) lightning data, the actual measurement only takes 18 minutes, which is about 703 times faster than the previous CPU single-line processing process, and the number of effective positioning points is only reduced by 9.3%.

Abstract:

In response to the current state and developmental requirements of HF(High Frequency) reconnaissance and localization, research work on the processing of ionospheric wave propagation multipath and polarization information has been conducted. This research investigates the simulation data of shortwave ionospheric multipath propagation delay and polarization matching, and quantitatively analyzes the relationship among the polarization state of the electromagnetic wave signal when it is received by the antenna, the polarization state when the electromagnetic wave signal is emitted, and the changes in the polarization state of the electromagnetic wave during its propagation in the ionosphere. A shortwave ionospheric multipolarization propagation model is constructed, and the research on the relationship between shortwave ionospheric multipath propagation delay and polarization matching is completed. The simulation results indicate that for shortwave signals, their polarization rate after passing through the ionosphere is only related to the angle between the propagation direction and the geomagnetic field.

Abstract:

A compact, high-gain ±45° dual-polarization patch antenna is proposed. A rectangular patch antenna operating in TM₀₅ mode is investigated and modified. The out-of-phase current portions of the patch are replaced by thin microstrips, minimizing the influence of the out-of-phase currents on the radiation pattern. Considering the one-dimensional antenna array configuration required in base station applications, the thin microstrips are meandered so that the proposed antenna structure size is significantly reduced compared with that of the traditional dual-polarized antenna. A pair of differential power dividers is utilized to replace the complex feeding network of the normal antenna array, thus simplifying the structure of the antenna. The simulated S₁₁ of the proposed dual-polarized antenna is less than -10 dB in the range of 3.4 to 3.6 GHz and the measured realized gain at the operating frequency range is greater than 11.3 dBi.

Abstract:

Metasurfaces have demonstrated extensive application potential in multiple fields. During the design of metasurfaces, it is necessary to optimize the components based on factors such as polarization, amplitude distribution, and phase distribution. This process typically requires the involvement of experts and is time-consuming. A method is proposed for inverse design of components that integrates high-precision ultra-wideband spectral forward prediction using neural networks and genetic algorithms. This method can simultaneously predict the amplitude and phase of a 16×16 high-degree-of-freedom discrete grid structure within the frequency range of 0.5~2 THz. The amplitude prediction accuracy can reach 0.019, and the phase prediction accuracy can reach 4.332°. The average optimization time for a single metasurface unit is 1.5 min. Two sets of 3 bit frequency-multiplexed and polarization-multiplexed metasurfaces are designed and simulated, and the simulation results validate the effectiveness of the proposed method. The method provides a new paradigm for the rapid design of components facing complex application scenarios and is of significant reference value to metasurface designers.

Abstract:

In battlefield communication confrontation, the rational allocation of interference parameters has always been a challenging task. Based on Deep Reinforcement Learning (DRL), this paper allocates the interference power, interference waveform, and interference target for the jammer, saving resource consumption and improving resource utilization while ensuring the effectiveness of interference. Specifically, the problem of interference parameter allocation is constructed as a fully cooperative multi-agent task. The SA(Stochastic Attention)-QMIX(Q-value based Mixing) algorithm is adopted to mitigate the issue of high decision-making dimensionality in multi-agent scenarios. By introducing the maximum entropy method and multi-head attention mechanism into the QMIX algorithm, the agents can make more effective collaborative decisions in partially observable environments. Simulation results show that when using the SA-QMIX algorithm for interference parameter allocation, compared with the traditional QMIX algorithm, it can increase the interference success rate by 5% while reducing the interference power by 1.5 dB. Moreover, the algorithm in this paper can converge faster, with the convergence speed being improved by approximately 40%.

Abstract:

Aiming at the problems of low efficiency and slow speed in current fall detection algorithms, a novel human posture-based fall detection algorithm is proposed. This algorithm obtains human skeletal key points information based on OpenPose and determines the human fall state based on three criteria: the descent speed of the center of gravity, the body tilt angle, and the deformation ratio of the body contour. During the experimental phase, compared with methods solely based on deep learning or wearable devices, the proposed algorithm shows the best performance, with a detection sensitivity of 98.35%, specificity of 96.79%, and accuracy of 97.11%. The experimental results verify the stability and reliability of the proposed algorithm, which has a broad application prospect.

Abstract:

Aiming at the problem of low accuracy in existing bird nest detection on transmission towers, a UAV(Unmanned Aerial Vehicle)-based bird nest detection system for power transmission lines based on the Lightweight Residual Convolutional Attention Network(LRCAN) is proposed. On the basis of analyzing the workflow, a bird nest detection model for power transmission lines based on LRCAN is proposed, which enables the network to focus more on the required detail features and suppress the interference of other irrelevant information. The normal convolution in the feature fusion network is modified by using depthwise separable convolution layers to reduce the number of network parameters. Simulation results show that compared with YOLOX-S, which has a similar number of parameters, the proposed model has increased the mAP(mean Average Precision) by 5.4%. Compared with YOLOX-L and YOLOX-X, which have the same level of mAP, the number of parameters in the proposed model is reduced to 1/5 and 1/10 of theirs, respectively.

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:

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:

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:

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:

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:

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:

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:

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:

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 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 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:

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 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:

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:

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:

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:

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:

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