Abstract:In THz range, most of the folded waveguide slow-wave structures are fabricated by microfabrication processes. The principal microfabrication processes for fold waveguide structure nowadays are discussed. The influence of microfabrication process errors including the depth a and sidewall profile on the high frequency characteristics of 0.41 THz folded waveguide slow-wave structures are analyzed. Through the analysis, the depth a shows great influence on the performance of folded waveguide Travelling Wave Tubes(TWTs), therefore, it should be controlled accurately in the process. The sidewall profile has little effect on the performance of folded waveguide TWTs when the angle is above 89°. The key processes are determined by simulation, which is helpful for developing THz folded waveguide TWTs.

Abstract:To improve the current and output power of terahertz Traveling Wave Tube(TWT), a Fundamental Mode Multi-Beam Folded Waveguide(FMMBFW) TWT scheme is proposed. Firstly, the high frequency characteristic is gained and compared with numerical simulation result. Secondly, the transmission characteristic of 60 periods FMMBFW is analyzed. Lastly, the beam-wave interaction characteristic of 0.14 THz FMMBFW TWT is completed by numerical simulation and theoretical calculation. When the DC current is 12 mA and the voltage is 15.75 kV, the 3 dB band of 0.14 THz FMMBFW TWT is 25 GHz(128 GHz-153 GHz), the maximum gain is 33.61 dB and the maximum output power is 23 W. When the DC current is 30 mA and the voltage is 15.75 kV, the maximum gain is 38 dB and the maximum pulse output power is 63.1 W at 0.14 THz. This method can effectively increase the current of FMMBFW TWT, and the interaction gain, efficiency, 3 dB band, output power can be improved. When the gain is the same, FMMBFW TWT can be fabricated more short and compact.

Abstract:Optical rectification of laser pulses in LiNbO3 by Tilted-Pulse-Front Pumping(TPFP) to fulfill phase match is a powerful way to generate terahertz pulses. A more detailed theoretical model for TPFP scheme is presented, which then is used to analyze the terahertz generation efficiency under different pump beam polarization states. A setup to generate high-peak-power terahertz pulses by optical rectification in LiNbO3 and a time domain spectroscopy system are established. The property of generated terahertz pulses is analyzed by using terahertz camera, and the results indicate that the peak power of terahertz pulses with 0.1 THz-2 THz frequency is 0.56 MW, and the generation efficiency is 0.56‰, which is consistent with the calculated result.

Abstract:A single-mode terahertz quantum cascade laser with metallic surface gratings is fabricated in order to obtain a terahertz source with narrow line width. Strong coupling efficiency and low waveguide loss are realized. A semi-insulating surface-plasmon waveguide is used to present a high output power. The lasing wavelength of this laser is 95 μm. The highest optical power of 43 mW and Side-Mode Suppression Ratio(SMSR) of 18 dB can be obtained under 10 K. Under the highest operation temperature of 70 K, an output power of 5 mW is still achieved. This kind of laser is the most promising solid-state source as the Local Oscillator(LO) for a high resolution terahertz heterodyne receiver.

Abstract:A 340 GHz 4-way fully integrated phased array transmitter using 0.13 μm SiGe Bipolar Complementary Metal Oxide Semiconductor(BiCMOS) technology is presented. The chip integrates a 21.25 GHz Phase-Locked Loop(PLL) synthesizer source，a quadrupler together with a 1:4 Wilkinson network，power amplifiers, analog phase shifters，20 Gbps OOK modulators, and a 2×2 on-chip antenna array in each channel. The phased array transmitter are measured and analyzed. The phase array beam scanning capability，3 dB lobe width，and system Effective Isotropic Radiated Power(EIRP) of ±12°,10° and 12 dBm in E-plane are obtained，respectively. The chip size of the fully integrated phased array transmitter is 8 mm×4.3 mm.

Abstract:The propagation characteristics of terahertz wave in non-magnetized and non-uniform plasma sheath are studied by the Scattering Matrix Method(SMM). The terahertz wave power reflection, transmission and absorption are simulated when the wave obliquely radiate the plasma, given that the electron density distribution of the plasma sheath is in double-exponential distribution. The variations of the terahertz wave power reflection, transmission and absorption with incident angle, terahertz frequency, plasma collision frequency and plasma distribution shape are summarized. The numerical results show that the terahertz wave has good propagation characteristics under these conditions. Overall, the transmittance of terahertz wave is better in plasma as its frequency increases, therefore, increasing the carrier frequency to terahertz band can be considered for solving blackout problem.

Abstract:THz atmospheric transmission is an important part of science and technology，which has permeated into almost all applications of terahertz technology. Research on terahertz atmospheric transmission is nearly on horizontal level in the existing literature. A dispersion attenuation model of terahertz atmospheric transmission is presented based on the radiation transfer, dispersion theory and Van-Vleck Weisskopf line-shape combined with Jet Propulsion Laboratory(JPL) database. The absorbing attenuation characteristics of terahertz atmospheric transmission along the slant path between 0.1 THz and 1 THz are studied using this model and compared with the existing literature. The influences of water vapor with different densities on the amplitude, phase and spectrum of the transient terahertz pulse are analyzed. Three relatively stable atmospheric transmission windows in 0.14 THz-0.17 THz，0.19 THz-0.32 THz and 0.32 THz-0.37 THz are obtained. This work has provided a theoretical reference for terahertz time-domain communications and space transmission.

Abstract:Single Carrier-Frequency Domain Equalization(SC-FDE) has been widely considered as an attractive technology for uplink broadband wireless transmissions because of its advantage of low peak-to- average power ratio. Based on a statistical model for channel estimation, the robust SC-FDE design with imperfect channel knowledge at receivers due to channel estimation errors is studied. The optimal equalization coefficients are derived under the criterion of minimizing the Mean Square Error(MSE) conditioned on a given channel estimate. Simulation results show that the robust FDE scheme achieves significant improvement over the conventional non-robust FDE scheme.

Abstract:Automatic Repeat reQuest(ARQ) scheme is one of the error control methods. There are two typical ARQ categories: the Selective Repeat ARQ(SR-ARQ) and the Go-Back-N ARQ(GBN-ARQ). SR ARQ has a much better throughput performance than that of GBN-ARQ, whereas its implementation is more complicated which results in heavy processing load. Both of the two methods can hardly satisfy the standards of wireless Asynchronous Transfer Mode(ATM). A novel ARQ scheme based on active fault tolerant is designed. It makes use of the statistical relationship of the control data from the network to recover the erroneous data. It is compared with conventional SR-ARQ and GBN-ARQ both in theories and in simulations of throughput performance. The results show that AFT-ARQ has a lower complexity than that of SR-ARQ；and it has a better throughput performance than that of GBN-ARQ，which is close to that of SR-ARQ.

Abstract:Single Carrier-Frequency Domain Equalization(SC-FDE) is effective to overcome multipath fading in digital communication and it is widely used for its performance. SC-FDE is adopted in broadband communication systems and a symbol transmission rate of 27.5 Mbps is realized under the carrier frequency of 137.5 MHz. The concatenated channel error correction coding of 1/2 rate convolution code combined with (239,223) Reed-Solomon(RS) code is used in order to improve the reliability of the system. The SC-FDE system is designed, and the key technologies of this system are analyzed. It is implemented on Field Programmable Gate Array(FPGA) hardware platform. The commissioning and validation are performed as well. The actual Bit Error Ratio(BER) test of the system is executed.

Abstract:Partial projection based interference suppression algorithm is proposed for cognitive Multiple-Input Multiple-Output(MIMO) system to achieve effective spectrum sharing between primary user and cognitive user. In this algorithm, spatial transmission characteristics of the primary user are introduced to the design of secondary user’s transmission. Based on analysis of structural characteristics of the interference, it is proved that the leakage signal from secondary transmitter to the idle dimensions of primary user is not harmful. Then the secondary signals are projected to the null space of low-dimensional subspace of interference channel between primary and secondary user to eliminate interference. Theoretical analysis and simulation results show that the algorithm effectively eliminates interference to the primary user; the secondary user’s transmission rate and the applicability of the algorithm have been significantly improved compared to the traditional method.

Abstract:An auto-adaptive tracking algorithm for fast moving target is put forward based on the improved traditional Mean Shift tracking algorithm, in order to achieve good tracking of fast moving target with variable scale. This algorithm firstly adopts the color image constituted by the pixels of target region with spatial weighting as initial frame object template, and the true position of target is obtained by the iteration of Mean Shift algorithm, therefore the spatial localization of fast moving target is realized. Then the features of adjacent frame targets are matched by Scale Invariant Feature Transform(SIFT) operator; the kernel bandwidth of next frame is updated in real time according to the scaling factor of target; the tracking window size of the algorithm is amended, which can adapt to the variable scales of the target, so the scale localization of fast moving target is achieved. Finally, the experiments demonstrate that compared with the traditional Mean Shift tracking algorithm, the tracking accuracy rate of the algorithm is above 97%, and the algorithm can accurately track the fast moving target with variable scales.

Abstract:The state of time domain electric field volume integral equation is good, while that of surface integral equation is poor, which results in slow convergence in the iterative solution of time domain electric field integral equation with volume-surface coupling, unable to meet the project requirements. Furthermore, the acceleration effect obtained by general preconditioning techniques is not very ideal. Therefore, a too long iteration time for time domain volume-surface integral equation has become the core issue in practical engineering applications. Aiming at the problem of poor behavior matrix, a new Block Matrix Pre-conditioner(BMP) method which can accelerate the convergence of matrix iteration is proposed. The time domain volume-surface integral equation matrix is decomposed into three pieces in the form of matrix multiplication, and the three matrices are all sparse. The efficiency of the preconditioning technique is illustrated by several volume-surface examples.

Abstract:The inject-locking on a magnetron is a key technique to achieve coherent power combining to extend the power capacitance of magnetrons. The improvement on the output spectrum of a 1 kW Continuous Wave(CW) magnetron at S-band is presented. The influence of the filament current on output characteristics of the magnetron is studied. The bandwidth of the free oscillating magnetron is reduced from 10 MHz to 300 kHz by decreasing its filament current. The inject-locking bandwidth of the CW magnetron has been expanded to 14 MHz by increasing the injection signal power. The External Quality Factor(QE) of the magnetron evaluated from the Adler equation varies from 52 to 72 at various injecting power ratios.

Abstract:It is difficult to describe the microwave heating procedure with accurate mathematical modeling since it is nonlinear and time-delayed. The existing microwave power control methods generally adjust and control parameters according to the results identified by the system. Because those methods feature a long transition time and low stability, a method of expert-Proportion Integration Differentiation (PID) active control on the source power of microwave is proposed. When 'thermal runaway' is prevented, the database of experts’ control rules is set up in line with such prior knowledge as dielectric properties and reflected power of materials. The control rules are in advance stored in the controller, so the problems of hard real-time control and low accuracy of control in the microwave heating procedure can be solved. Compared with the classical PID control, the simulation findings show that the expert-PID control saves about 70% of time taken to reach the state of being stable, improves the efficiency by 89% and increases the accuracy by 87%.

Abstract:A method of designing X-band low phase noise frequency synthesizer is proposed. By combining the mixer-Phase Locked Loop(PLL) and the analog of high order multiplier, the hopping signal of X-band is realized. The synthesizer can achieve specifications including spurious-suppress below -68 dBc and phase noise below -99 dBc/Hz@1 kHz, -104 dBc/Hz@10 kHz, -106 dBc/Hz@100 kHz. It emphasizes the key techniques of low phase noise multiplier using step recovery diode, and analyzes the method of implementing specifications. Through the measured results, it is demonstrated that the method can design the X-band low phase noise frequency synthesizer achieving the given specifications.

Abstract:Reflection coefficient of the active device is the main parameter which directly affects the output power of the signal. The two methods－impedance tuner and Vector Network Analyzer(VNA) frequency shift , are analyzed in order to measure the reflection coefficient of active device on the state of "RF ON". Some measurement experiments on the signal generator and amplifier are performed. The results show that, the difference between the two methods is less than 0.06，and the phase difference is below 10°, under 10 dBm of the output. The work provides feasible ways to measure the reflection coefficient of active devices.

Abstract:Pose and illumination variations are two major challenges in face detection. Therefore，a novel face detection method based on differential features is proposed. This method extracts first order and second order differential features from images, which are respectively used to train two face detectors using the Gentle Adaboost algorithm with the Classification And Regression Trees(CART) as weak classifiers. Given a new image, the two face detectors are first separately applied to detect candidate faces in the image, and then their detected face regions are combined to give the final face detection results. Thanks to the illumination invariance of first order derivative features and to the rotation invariance of second order derivative features, the proposed differential features based face detection method can better handle the detection of multi-view faces in complex background. The proposed method has been evaluated on the CMU-MIT and FDDB datasets and the results demonstrate its effectiveness.

Abstract:A keyword extraction algorithm for Chinese documents based on frequent pattern mining is proposed aiming at the problems of existing Keywords Extraction Algorithm(KEA) including high computational complexity and mining shallow semantic information. This algorithm adopts improved FP-Growth technology to extract word co-occurrence information and remove noisy words. It utilizes semantic similarity algorithm to eliminate synonyms and simplify the characteristics of candidates, thus reducing the storage space and the amount of calculation when ensuring the high precision and recall. Experimental results show that the average F value of corpus reaches 59.7%, which is higher than classical algorithms; and that the support threshold is the vital influencing factor.

Abstract:Recognition of quartz and feldspar is meaningful for reservoir research. Traditional mineral composition analysis mainly relies on the man-machine interactive identification, which brings enormous work as well as low efficiency. Considering above problems, an effective dividing method is proposed in this paper based on rock particles' texture characteristics under orthogonal polarizer. The gradient information of sample images is firstly extracted using Sobel operator. And Gray Level Co-occurrence Matrix(GLCM) energy and relevance of each gradient image are calculated as the characteristic parameters sample library. Then apply Artificial Neural Network(ANN) classification methods to training. Based on the training data，the particles is identified according to the characteristic parameters. At last, polarized sequence diagram is used to decide the final recognition result. The experimental results indicate that the method of recognizing quartz and feldspar achieves good effect.

Abstract:The exsiting example-based super-resolution algorithms of face image adopt global search, which causes the problems of non-local mismatch and poor visual effect of image restoration. A new matching and learning-based face image super-resolution restoration algorithm is proposed. A pre-classification process of input image is applied to get a sub-sample library from the image library, and the corresponding feature images are created. In the matching process, two new search strategies for different face images are used, which consider the similarity and consistency between image patches and make the recovered image look more coherent and natural. Experimental results show that the proposed algorithm synthesizes high-resolution faces with better visual effect and obtains higher values of the average of Peak Signal-to-Noise Ratios(PSNR) when compared with other methods.

Abstract:Curved Point-Normal(PN) triangles or the similar PN quads are both efficient ways to enhance realism in 3D rendering through tessellating every input triangle or quad into smaller triangles based on tessellation factor and soften triangles’ shared edges by using Bezier techniques. With the support of tessellation in modern GPU(Graphic Processing Unit) architecture and graphics library (e.g. DirectX 10 and 11), the PN triangles or quads has neither special requirement on rendering pipeline nor modeling tools, and it can produce soft silhouette and efficient rendering result by using vertex position, normal information, adaptable Load of Detail(LoD), and possible Normal Map or Displacement Map.

Abstract:The OpenGL viewpoint control is one of the key techniques to determine the space situational visualization. The principle of OpenGL viewpoint coordinate system is introduced firstly. Secondly, a viewpoint control algorithm based on the spherical coordinates is put forward, which realizes the viewpoint transform between the spherical coordinates and Cartesian Coordinates since the view function interface is based on the Cartesian coordinates system. Then, the viewpoint translation, rotation and scaling in spherical coordinates are derived. The application of the viewpoint control method in the space situation scene are introduced.

Abstract:Long-term free-riding behavior of Peer to Peer(P2P) systems makes the system gradually lose its original distributed shared characteristics. In order to prevent selfish behaviors, a new evaluation model for P2P systems is proposed based on the characteristics of game theory suppression model and incentive-based node behavior model. The reputation value which reflects the period performance of users is adopted to characterize user-behavior, and some confinement conditions are set to prevent generating selfish nodes. The various kinds of incentive mechanisms in P2P systems are mathematically modeled and fitted with Auto-Regressive(AR) model. The simulation results based on this model show that the behavior of the system evaluation changes periodically; and the satisfaction is stabilized to a smooth number, 30%.

Abstract:Cam phaser is vital to increase the efficiency of engine. The maximum corner, friction torque and leakage are important parameters to influence the performance of Variable Cam Phaser(VCP). For the sake of testing these three parameters，the overall structure，the principle of the measurement and work flow are introduced. The industrial control computer, acquisition card and expandable modules are selected to set up electricity control system. Laboratory Virtual Instrumentation Engineering Workbench(LabVIEW) is selected to design upper computer. The test bench can measure VCP，perform conformity judgment，classify VCP after measurement, execute data statistics and create the report form all automatically.

Abstract:There exist various kinds of low level indices and uncertainty of evaluation information in the capability evaluation for air traffic control system. To solve this problem，a novel evaluation methodology using Dempster-Shafer(D-S) evidence reasoning is proposed. Firstly, the rule base is built with belief structure, and the input information is transformed into a pre-defined form. Then the activation weight of input is calculated. After that, the final assessment distribution is obtained by using evidence reasoning for index aggregation. The capability evaluation of a certain air traffic control system is investigated, so as to illustrate the feasiblity and effectiveness of the new methodology.

Abstract:Core scanner is used widely in the petrol or geological departments at present, although there is still lack of device that can monitor working status and control core scanner more conveniently. Several kinds of 2.4 GHz wireless communication methods are compared, and a design scheme of wireless monitor system for core scanner based on ZigBee is proposed. CC2530 is used as the core component of the system. The hardware and software of the system are designed in detail. Related test results show that this system can monitor temperature and humidity of the core scanner and also can control it wirelessly. The proposed system can organize network fast with good reliability.

Abstract:The establishment of an information management system is very necessary under the global popularization of Internet and the sharing of information resources conditions. Focusing on how to design an efficient, fast, high-quality operation monitoring system, four aspects are studied including the business architecture, application architecture, data architecture and technical architecture, and the function for each architecture is designed in detail and analyzed. A whole system design route is formed through integration, which can lay a solid foundation for the design and implementation of monitoring system in the future.

Abstract:Because the tethered balloon has the characteristic of floating for a long time in the sky, the control system must be of safety and reliability. Four aspects are considered including the redundancy, emergency response capability, fast replacement and electromagnetic compatibility for the design of ball control computer. The redundancy designs are conducted on the data processing, pressure detection channel and data transmission channel based on modularized network. The emergency response and electromagnetic compatibility are designed as well. Failure free operation lasting for several months has validated the high reliability and safety of the proposed control computer.

Abstract:The inertia force sensing characteristics of FBAR(Film Bulk Acoustic wave Resonators) micro- accelerometer sensor are studied, which integrates inertial force sensing structure of silicon micro mass-proof and cantilever beams with AlN(Aluminum Nitride) FBAR detecting elements. The stress distribution of silicon micro supporting beam under the inertia force loads are obtained by applying Finite-Element Analysis(FEA) static simulation. Then the maximum stress value is selected as load, the relationships between elastic coefficient and stress of wurtzite AlN are calculated according to the first principles. Therefore, the maximum variation of AlN elastic coefficient under the inertia force load can be predicted. Next, the micro-accelerometer frequency characteristics and the tendency of FBAR micro-accelerometer are predicated through the analysis of harmonic response. It is concluded that the resonance frequency of FBAR micro-accelerometer shifts to a higher one under an inertial load, with a sensitivity about kHz/g; and there exists a good linearity in the acceleration increment-frequency shift characteristic curve.

Abstract:It is very difficult to establish high-fidelity model for self-actuation failure threshold power of switch when considering the fringing field effect of the electric field distribution of the capacitive RF MEMS(Radio-Frequency Micro-Electro-Mechanical System) switch membrane. Therefore, in order to characterize the intensity of the fringing field effect of the electric field distribution on the membrane, the Figure of Merit(FoM) is constructed by using the ratio between the area of the switch membrane subjected to RF power(ARF) and the facing area(A) (which is between the membrane and the transmission line). The three-dimensional electromagnetic model of self-actuation failure of the switch is constructed by using the HFSS(High Frequency Structure Simulator) software. For a case of a common configuration of the switch, the distribution of fringing electric field of membrane under a variety of RF signal powers (Pin) and with different air gaps of the switch(g0) are obtained through simulation. The comparison between the calculation of FoM and simulation results indicates that it is feasible to characterize the intensity of the fringing field effect of the electric field distribution of the membrane by using FoM(ARF/A).

Abstract:A certain component is a kind of multilayer narrow gap container. To test the vibration of slab induced by flowing water at high speed in this component, a shielded eddy current sensor is designed based on the eddy current principle. The coil parameters of the probe and the structure parameters of probe’s shell are optimized for the proposed shielded eddy current sensor. The assembly and debugging, as well as the calibration of the third party, are performed. The test results show that: the proposed shielded eddy current sensor, which has no interference to the flow field and no breakage to the structure of the device, can realize the vibration test of slabs with narrow gap reliablely and efficiently.

Abstract:With the development of satellite based remote sensors, embedded systems become more and more popular in space camera electronics. Static Random Access Memory(SRAM) is one kind of the most widely used memories due to its merits of high efficiency and low power dissipation, but testing its function still depends on writing testing modules with hardware description language, which results in low developing efficiency and low reliability. In this paper, an embedded testing method is proposed, which is based on MicroBlaze and its speed increasing function design. Implementation of the test method is based on reusable Intellectual Property(IP) technique and greatly improves data transfer speed. With this method, secondary development of SRAM test system can be made in application layer instead of fundamental logical layer, which simplifies the system design. It is not only more efficient and more reliable, but also easier to transplant, which greatly reduces test design cost. The validity and feasibility of the method have been proved by test results.