Abstract:A planar Schottky Barrier Diode(SBD) with the Schottky contact diameter of 1 μm fabricated using electron beam lithography method is reported. The DC measurement results show that the DC series resistance, the junction capacitance and the cut-off frequency of SBD are 10.2 Ω, 1.76 fF and 8.7 THz, respectively; the RF extracted series resistance of 15.4 Ω, the junction capacitance of 1.46 fF and the cut-off frequency of 7 THz are also demonstrated.

Abstract:The research and development activities of near-terahertz linear beam vacuum electronic devices are described, including slow wave structure theory, parts design, simulation and optimization, micro-fabrication and micro-assembly techniques, tube integration technologies, etc. These devices include Traveling Wave Tubes(TWTs), Backward-Wave Oscillators(BWOs), clinotrons, Stop-Band Oscillators and TWT harmonic amplifiers, etc with folded waveguide and vane-loaded waveguide as high frequency interaction structures. The devices technologies are mainly composed of Micro Electro Mechanical System(MEMS) technology, Microwave Plasma Chemical Vapor Deposotion(MPCVD) diamond process, metallization and mounting technique, etc. Finally, specifications of devices at W-band, 220 GHz and 340 GHz frequency bands are given.

Abstract:Solid-state doubler is the crucial component in terahertz source application. How to make use of nonlinear devices to improve the conversion efficiency of terahertz doubler is the key to design terahertz solid-state circuits. Two design methods of solid-state terahertz doubler are introduced and two different topology structures of 170 GHz doubler are designed. The direct matching method and the transmission mode matching are employed respectively in the two different 170 GHz doubler topologies. Based on the two structure models, 3D finite element simulation and nonlinear harmonic balance simulation are carried out. Simulation results indicate that the conversion efficiency of the doubler is above 15% and the output power is up to 7 mW within 160 GHz-180 GHz output frequency when driven by 17 dBm input power. Simple comparison and analysis are made between the two doubler structures designed by two different matching methods, which lays foundation for the future terahertz doubler design and research.

Abstract:Terahertz(THz) filters with mirrored asymmetric metamaterial structure have been studied based on the micro-nanofabrication technology. According to the finite difference time domain theory, the electric field and current density distribution of the microstructure are simulated and analyzed. The mechanisms of THz electromagnetic resonance of THz filter and physical mechanism of THz radiation loss are also described. The asymmetric split ring of micro-structures is designed and optimized in order to reduce the radiation loss and improve the Q value of the quality factor. The performance of the THz filter is characterized in the THz Time Domain Spectroscopic(THz-TDS) system. It is found that the quality factor of the filters with mirrored asymmetric metamaterial reaches up to 12.5 at the frequency of 0.923 THz. At the same time, the dependence of the direction of THz electric-field E on the performance of THz filter is studied as well. The study of the THz filter provides an important experimental basis for the development of THz devices, such as electrically tunable THz modulator.

Abstract:Scintillation induced by atmospheric turbulence is an important factor affecting the performance of terahertz wireless communication system. A space diversity scheme is proposed to improve the performance of terahertz photon-counting wireless communication system which is influenced by strong atmospheric turbulence and noise. The Bit Error Rate(BER) expression of transmit diversity system, receive diversity system and Multiple-Input Multiple-Output(MIMO) system in strong turbulence channel are respectively derived. The numerical simulation results show that spatial diversity techniques which can be used to antagonize strong atmospheric turbulence effectively and reduce the BER of the communication system, is a simple and effective approach to improve terahertz wireless communication under adverse weather conditions.

Abstract:Biological functions of biological organic molecules must be achieved in their solutions. Terahertz wave is very sensitive to water and it can detect changes of the water dynamics of biological molecules directly in hydration layer between water and solute molecules. Thus, Terahertz Time Domain Spectroscopy(THz-TDS) technology is an ideal tool for the detection and research of biomolecular organic solutions. In this paper, THz-TDS is used to research the molecular structures of glucose. The absorption spectrum of glucose and its solutions of various concentrations are obtained by THz-TDS and Fourier Transform Far Infrared(FTFIR) spectrometer in nitrogen or vacuum environment at room temperature, respectively. The results show that distinct characteristic absorption peaks of glucose solutions are found at far-infrared range. Solutions of glucose with different concentrations show different absorption to terahertz wave. In consideration of works above, THz-TDS can provide a new method to identify glucose and its solutions of various concentrations.

Abstract:The important influence of cloud on climate change, and the common remote sensing method of cloud measurement are introduced, then the absorption spectra of THz wave and the scattering characteristics of cloud particles are studied. By comparing with the traditional cloud detection technology, the advantages of space-borne terahertz cloud radar are analyzed. Finally, the feasibility analysis of the radiation source for space-borne terahertz cloud radar is presented.

Abstract:The loss of the folded waveguide slow wave structure is significant in the terahertz regime, which is necessary to be well studied as designing the slow wave structure of a folded waveguide Traveling Wave Tube(TWT) at 220 GHz. In this paper, the S parameters of the slow wave structure are predicted firstly by simulation, and then the sample of the slow wave structure is fabricated by Ultra Violet-Lithographie, Galanoformung, Abformung(UV-LIGA) process and measured. The measurement result shows that the attenuation factor of the sample is about 240 dB/m at 220 GHz, which is reasonably consistent with the simulation result. The micrographs show that there is a discrepancy between two results at higher frequencies due to the sample deformation.

Abstract:The principle of encoding and decoding for Turbo code and the Log-MAP decoding algorithm are introduced. The encoding and decoding processes are implemented on the Altera DE4 development board and the parameters of the encoder and decoder are based on the 3GPP Long Term Evolution(LTE) standard，which can work with any code length in LTE physical link. Finally，a simulation platform is built. The data from hardware implementation and simulation are compared to verify the feasibility of this implementation.

Abstract:Chinese standard Digital Television Terrestrial Broadcasting(DTTB) signals have become a hot radar emitter due to their remarkable advantages such as high transmitter power, large coverage area, and wide signal bandwidth. However, in consequence of the periodic repeat of signal frame head, it inevitably generates periodic side peaks during ambiguity function analysis, which directly affects the signal detection performance. Therefore, it is essential to suppress side peaks. With the development of the technology, the acceleration of target reconnoitred increases continuously, which makes the acceleration to be an important factor and can not be ignored. Nevertheless, the influences of acceleration have not been considered in traditional side peaks suppression algorithm. In this paper, a new side peaks suppression algorithm based on target acceleration is presented to suppress side peaks caused by DTTB signals periodic repeat. The simulation results show that this method can effectively suppress DTTB signal range and Doppler peaks.

Abstract:With the rapid development of deep space exploration，satellite navigation and satellite remote sensing technology, higher data processing rate and stronger anti-interference performance are required in space communication. Therefore，communication with higher frequency spectrum utilization and stronger anti-interference will be the brilliantly prominent consideration in the future space environment. In this paper，the restriction factors on the performance when transmitting data are analyzed firstly, then the principle，the performance and application of new modulation and coding technology are explained in detail. Finally，a scheme that combines novel modulation and coding technology is proposed under complex electromagnetic environment. By analysis，it is shown that the combined scheme can improve the spectrum utilization and anti-interference performance.

Abstract:A fully differential line driver, with high linearity is presented，which is applied in narrowband Power Line Carrier Communication(PLCC). The proposed configuration includes a preamplifier with programmable gain and a power output stage. The preamplifier features an adjustable output swing, and the static power consumption can be switched by output stage according to power detection circuit. The proposed line driver is deigned based on Semiconductor Manufacturing International Corporation(SMIC) 180 nm Complementary Metal Oxide Semiconductor(CMOS) technology. Post-layout simulated results show that the maximum current driving capacity is up to 660 mA and the Total Harmonic Distortion(THD) is less than -60 dB when peak-to-peak value of output swing is 4 V, which meets the requirement of narrowband power line carrier communication.

Abstract:In order to solve the problem of accuracy decrease of Direct Position Determination(DPD) in the presence of gain-phase error, the effect of the gain-phase error on the DPD algorithm is analyzed, and an improved DPD algorithm with gain-phase error is introduced. In this algorithm, array response vector is compensated by the correction results of gain-phase error, and the target location is estimated by DPD algorithm. Simulation result shows that the improved algorithm has higher accuracy than the DPD algorithm without correction.

Abstract:Based on the analysis of inter-satellite distance and clock error computation, the error expressions caused by the relative motion between the satellites are deduced, which provides a theoretical basis for relative motion error elimination. An ideal result of relative motion compensation can be obtained by simulating the relative motion error and using Doppler measurements. In the case of Global Navigation Satellite System(GNSS) constellation, the deviation of clock error measurement can be reduced to 0.001 ns with the proposed method, which can vastly guarantee inter-satellite measurement accuracy and time synchronization precision in the future.

Abstract:The navigation pseudo random long code period is 7 days generally. When the time uncertainty is ±1 s and the code rate is 10.23 MHz, the chips needed to search are up to 20 460 000. So it is difficult to realize acquisition in short time with common methods. By increasing the consumption of hardware resource and reducing the coherent integration time, the acquisition speed will be increased. Nevertheless this will lead to the decrease of the acquisition sensitivity due to the limited hardware resources. In order to realize the acquisition quickly without affecting the acquisition sensitivity with the limited hardware resources, the two-dimensional parallel search method based on Fast Fourier Transform (FFT) is presented. By comparing with the methods of code phase parallel searching based on FFT and matched filtering +FFT in three aspects: acquisiton time, sensitivity, and hardware resources, the proposed algorithm is demonstrated to have advantages of fast acquisition speed, high sensitivity, and rational use of the hardware resources in the long code acquisition.

Abstract:Spaceborne Synthetic Aperture Radar(SAR) obtains electronic image of the earth's surface using electromagnetic waves. For it is side-looking imaging, SAR image inherently contains geolocation error caused by SAR image acquisition geometry, imaging mode, scattering properties and image formation process. These errors should be considered and corrected for SAR image utilization. Geolocation accuracy of spaceborne SAR image and geometric distortion can be improved and corrected by using prior control point. The system error transfer law of spaceborne SAR image geolocation is analyzed. An improved system error correction model is proposed by combining the system error sources with similar error transfer characteristics. Monte-Carlo simulation results show that the new model has higher correction accuracy of system error.

Abstract:A basic model of target detection and tracking of photoelectric image has been analyzed to solve the problems existed in target detection and tracking of photoelectric image in complex background. The distance information is divided into three categories including scalar distance information, vector distance information and array distance information according to spatial dimensions and the amount of contained information. The distance information processing method oriented target detection and tracking in optical information has been researched systematically. The relationship between the target scale in photoelectric image and the scalar distance information is obtained. The image matching method using the high-level feature matching model in photoelectric image is expanded from 2D to 3D space. The applications of array distance information in target detection and recognition are summarized. This work can provide a theoretical basis for target scale analysis, image matching and identification of target species in photoelectric images.

Abstract:The signal processing circuit in pulse taut wire magnetic axis measurement system is improved in order to improve the measurement accuracy. Firstly, The reason of signal distortion is analyzed according to the amplitude frequency and phase frequency responses of the circuit. Then the theoretical computation results show that the Tilt error caused a 30 Hz square wave, and the Offest error caused an extra 5 ms pulse at the edge of the square. The proposed signal processing circuit, which can transfer signals from 30 Hz to 3 000 Hz undistortedly, satisfies the demands of this system. The measurement results show that the axis Tilt and Offest errors are easily to distinguish, and the measurement error is reduced.

Abstract:A new type of profiled horn with contour constituted of three kinds of curves is presented and simulated. Its radiation performance shows good circular symmetry，low sidelobes，low cross-polarization and high Gaussian coupling efficiency. In the frequency range of 39 GHz-42 GHz，the return loss is below -20 dB, the antenna radiation efficiency approaches to 100%, and the coupling efficiency reaches 98%, which is comparable to the performance of corrugated horn. Therefore it can be used as an efficient Gaussian beam launcher to take the place of corrugated horn which is relatively complicated and costly.

Abstract:A new monopulse antenna is designed and analyzed based on quasi-optical technology at sub-millimeter wavelengths. The radiation performances of the proposed monopulse antenna are rigorously investigated by combining the Finite Difference Time Domain(FDTD) method and the Stratton-Chu formula. In order to suppress the side lobe levels of sum radiation patterns, a modified hyperbolic-plano dielectric lens with cutting segments is introduced. The simulated results show that this monopulse dielectric lens antenna has good radiation characteristics with the side lobe levels below -11.9 dB in sum patterns, the maximum null-depth below -30.0 dB and the amplitude imbalance below 0.50 dB in difference patterns.

Abstract:Digital core image analysis technique is utilized in the core physical study in order to solve the problems such as time-consuming and difficult to reproduce of the core physical properties experiments. Taking the two-dimensional(2D) slices of the core as the training images, a three- dimensional(3D) image is reconstructed by the simulated annealing algorithm. A 2D image sequence of the same series is acquired by Computed Tomography(CT) technique. The pore structures are extracted from these two sets of images. Pore-throat sizes and their distribution are calculated by maximal balls model. By comparing the results with that of the mercury intrusion method experiments, distinctions and reasons between the current digital core analysis technique and traditional core physical properties experiments are analyzed. Results show that the large pores could be depicted in 2D slices and CT images. However, the core physical properties experiments are able to measure the size of micro pores, while the digital core reconstruction method could not due to the limitations of imaging equipments.

Abstract:Feature extraction is the key technology in the field of image and voice recognition or fault diagnosis. Having deeply studied the advantages and disadvantages of the feature extraction based on the wavelet transform and Empirical Mode Decomposition(EMD), a method combining advantages of the two methods is proposed to extract the feature information. Firstly, the proposed method acquires stabilized single mode state components by EMD, and then Wavelet Packet(WP) analysis is performed to single mode state components. Finally, by comparing the method with other methods through simulation and example test, it is proved that the proposed method not only features higher feasibility, but also can extract fault information more accurately.

Abstract:The principle and basic programming syntax of firewall tool―netfilter/iptables and traffic control tool―Traffic Control(TC) based on Linux are analyzed. According to features of small-scale Local Area Network(LAN), a network management system is proposed. This system implements packet filtering and network IP address translation by iptables, and implements traffic control by Hierarchical Token Bucket(HTB)-based TC. Test results indicate that the proposed system based on iptables and TC can effectively protect network security, reasonably constrain the bandwidth of network devices and ensure quality of services.

Abstract:The development of small total phosphate testing system and the study of phosphate electrode are proposed in order to optimize the pretreatment system of small water sample digestion. Digestion is performed for each electrode before testing. A digestion pretreatment system for water treatment based on ultraviolet photo-catalytic method is optimized. A 254 nm wavelength UV light is used in this system, and gold is selected as sensing material. The volume of digested water sample or actual sample is measured. These electrodes are applied to detect total phosphorus concentration in water samples from lake. The experiment results demonstrate that the system shows high sensitivity in the concentration range of 0.1 mg/L–1.0 mg/L(R2＝0.993 3) and a low detection limit (0.1 mg/L) in the slope around 1.477 0 μA/(mg?L-1). The proposed total phosphate testing system bears the characteristics of small size, low power consumption, high digestion efficiency and has no need of strong oxidizing agent, which is expected to be used for online-monitoring of total phosphorus.

Abstract:The ability to perceive the vehicle’s local environment is one of the main challenges in the field of Unmanned Ground Vehicles(UGV). Many kinds of positive-negative sensors are used to obtain the information of the vehicle’s local environment. The environment perception system is in charge of processing, fusing and understanding the information. The system also realizes the detection of road and obstacles and the classification of terrains. Autonomous navigation and path planning of UGV are based on the process results of perception system. In this paper, the architecture of environment perception system is introduced. The methods of road detection and obstacles detection are discussed, and then the detection results of these methods are analyzed. The existing problems and the future development trends of the environmental perception system are summarized and prospected at last.

Abstract:Message-digest algorithm is widely applied in the field of e-commerce and information security，and its unidirectionality and collision resistance are the keys to the algorithm. By using splitting and summing of integer vector，combining with the irreversibility of data interception and extensibility of nonlinear transform matrix, a new message-digest algorithm is constructed. The algorithm is described，discussed and verified through designed test cases. Test results show that the algorithm can achieve the desired effect. with the advantages of being concise，flexible，logical and widely applicable.

Abstract:Different types of nano-cantilever specimens are fabricated from a macroscale multilayered thin film(silicon/copper/silicon nitride, Si/Cu/SiN) by using the Focused Ion Beam(FIB) based on the cantilever bending method in order to investigate the cracking behavior of nanoscale interfaces. For the single-mode interface cracking, a straight nano-cantilever specimen is fabricated. For the mixed-mode interface cracking, a double-nano-cantilever specimen is proposed to simultaneously apply bending and torque moments to the interface. All specimens are in situ loaded in the Transmission Electron Microscopy(TEM). In straight nano-cantilever specimens, the Cu/Si interface fractures due to a bending moment. In torsion nano-cantilever specimens, by changing the loading position, fracture experiments with different mode-mixities are successfully conducted. In addition, finite element analysis is employed to inquire the critical stress distribution on interface during the crack initiation, and stress concentration regions near the interface edge in all specimens are within the scale of 100 nm. In straight nano-cantilever specimens, the interfacial normal stress dominates the interface cracking, indicating a single-mode fracture. In torsion nano-cantilever specimens, the critical normal and shear stresses at crack initiation have a circular relation.

Abstract:Switch current stress of the traditional resonant-type bi-directional full bridge DC/DC converter will surge when the energy pushes reversely. A new kind of inductor–capacitor–inductor(LCL) composite resonant-type bi-directional full bridge DC/DC converter is proposed, which ensures that the current stresses of switches always keep low. The working principle of the resonant converter is elaborated. The AC impedance model of the converter is established, and the method of parameter design is given. Furthermore, the output control of the converter is realized through energy injection and free oscillation control strategy. The experimental result shows that the proposed control strategy is feasible.

Abstract:Thermal batteries have been widely used for military use due to their high specific power density and long storage life. With the development of electronic devices miniaturization, smaller and thinner thermal batteries are being studied as potential power sources for some special applications. Thin film FeS2 cathodes prepared by rolling and coating are compared with the FeS2 pellets shaped by traditional pressing. The discharging capacities of FeS2 thin films(thickness=120 μm) are 821 mAh?g-1 and 528 mAh?g-1 respectively with different current densities of 100 mA?cm-2 and 1 A?cm-2. The results show that the FeS2 thin films have a 20%-30% higher capacity than the pellets manufactured by traditional pressing, and the resistance of thin film thermal battery is only 81 mΩ. In addition, compared with the traditional thermal battery, the discharge capacity of thermal battery piled by thin-films is increased by 153%, and the weight and volume are reduced greatly.

Abstract:The new process of laser technology combined with manual and automatic acid decapsulation is applied to decapsulation experiment of small, heteromorphic and multichip plastic encapsulated microcircuits. The laser etches the encapsulation materials above the chip accurately and incompletly, and then combines with manual and automatic acid decapsulation to remove the rest encapsulation material on the chip surface. The experimental results show that the manual and automatic acid decapsulation time is 8 s after laser decapsulation. Comparing with the traditional acid decapsulation, the laser technology in decapsulation of plastic encapsulated microcircuits can achieve accurate positioning, shortening the time of decapsulation, and improving the efficiency.