Abstract:The technique features of Unmanned Aerial Vehicles(UAV) terahertz wave Synthetic Aperture Radar(SAR) imaging were analyzed．The relation among average power of radio transmitter，resolution in azimuth，maximum range migration, strip width and other parameters of SAR in typical frequency bands was discussed．For multiple scatter targets，based on the Range-Doppler algorithm，the imaging simulation was conducted to verify some operation characteristics of UAV THz SAR and obtain high resolution radar image(0.3 m×0.3 m)．
Abstract:Aimed at wide-band linear frequency modulation(LFM) radar，a method of image deception signal generation was put forward. Via the analysis of the demodulation of radar echo, the expression of the image deception signal was obtained. Then, a solution based on Digital Up Converter(DUC) was proposed, which implemented the conversion of a complex digital baseband signal to a real passband signal. Through the analysis by using high performance spectrum analyzer and image software, the validity of this method to generate jamming picture(400×400 pixel) was proved.
Abstract:Maximum tracking capacity of phased-array radar is not only a key system index, but also the base of Track-And-Search(TAS) mode. In order to analyze the parameter from an engineering aspect, firstly, the relationship between revisit-time and engineering measurement error was researched, and tracking illuminating time with minimum Signal to Noise Ratio(SNR) requirement was analyzed in detail with the assumption of Singer model. Secondly, with the help of statistic analysis under multi-target environment, the statistic mean revisit-time and the statistic mean illuminating time were given to compute the maximum tracking capacity of phased array radar under saturation state. Furthermore, a formula was given to compute dynamic tracking under radar saturation state. Lastly, a simulation software was developed by VC++ and the related conclusions were validated on the simulation software.
Abstract:In order to improve the stability and reliability of Synthetic Aperture Radar(SAR) images matching, a new scene matching algorithm for SAR images based on Scale Invariant Feature Transform (SIFT) features was proposed. Numerous experiments were conducted for homologous and non-homologous SAR images under various conditions, and the preliminary matching conclusions were obtained. The experimental results demonstrates that the proposed approach is stable，reliable，efficient and robust for the data used in the paper.
Abstract:The Radar Electronic Warfare(REW) simulation system based on computers is used to research and evaluate the jamming modes and jamming signals generally. A REW simulation system adopting the software of VC++ and MATLAB was introduced in the study. The barrage jamming and the deception jamming to radar could be realized, and the jamming effect could be evaluated by the simulation system. The structure and the realized method of the simulation system were analyzed, and the key technologies were discussed in detail. Finally, a simulation experiment was performed under the given scene. The simulation results proved the validity and the practicality of the simulation system．
Abstract:The integration of the radar/communication and EW system is the inevitable result of electronic technology development and modern war requirement. The integration of electronic warfare equipment is high-tech system connect ideas for modem material science, photon science, microelectronics, photoelectron technique，micro-machinery technique，especially computer hardware and software，as well as software radio-technology，etc. This paper analyses the main features，development trend and some key technologies for accomplishing the integration of radar-electronic warfare.
Abstract:In order to overcome the slow convergence rate and bigger mean square error of Feed-forward Neural Network(FNN) blind equalization algorithm，a FNN blind equalization algorithm based on Orthogonal Wavelet Transform(OWT) was proposed. In the proposed algorithm, orthogonal wavelet transform was prosecuted on input signal of FNN equalizer to reduce the correlation of the input signal by using the de-correlation ability of wavelet transform. Accordingly, the proposed algorithm could improve the convergence rate and reduce the mean square error. The simulation results of underwater acoustic channels showed that the proposed algorithm outperformed FNN blind equalization algorithm in the convergence rate and mean square error.
Abstract:In recent years，left-handed metamaterials have been extensively studied due to their unique properties. A new kind of structure with left-handed electromagnetic characteristics was designed and analyzed. It was composed of dielectric resonators working at transverse electric resonant mode, which were embedded into a parallel plate waveguide. It worked well from 12 GHz to 14 GHz，and the transition frequency was at 13.15 GHz. The proposed metamaterial demonstrated a good transmission performance with insertion loss less than 0.6 dB and low pass-band ripples. Compared with conventional CRLH structures，the structure is simple and with low insertion loss, low conductor loss at high frequency band. It can be applied to super lens and antennas in future.
Abstract:In the perspective of communication countermeasure, by the way of frequency analysis, this study analyzed the effect of noise jamming signal on Time Hopping-Pulse Position Modulation-Ultra Wide Band(TH-PPM-UWB) communication system. The jamming results of noise jamming signal to the Ultra Wide Band(UWB) communication system were simulated in the Monte Carlo experiment by MATLAB program, and the relationship among the signal power, bandwidth, center frequency and Bit Error Ratio(BER) were given. It has laid the theoretic foundation for manufacturing practical equipment.
Abstract:With its extending applications，Synthetic Aperture Radar(SAR) is required to process more and more data. The processing speed of traditional SAR processor turns out to be a bottleneck of the extension of SAR applications. Highly efficient SAR signal processors need to be explored towards these challenges. Recently，Graphics Processing Unit(GPU) is developing at top speed，which is a novel and promising computation platform for efficient SAR processors. A GPU-based SAR signal processor is introduced in this paper. The implementation of this processor takes full advantage of GPU′s computation capability, using general purpose computations to implement the SAR imaging based on CUDA programming model. As the result shows, this processor is more than ten times as fast as traditional CPU-based SAR processor. It provides a promising way to solve the problems of SAR signal processing in the future.
Abstract:Focusing on the illumination coherence problem of the three-dimensional virtual scene, this study analyzed the environment mapping technology to improve the sense of reality. The light probe image was used to light the scene and the irradiance of the diffuse surface was approximated by using spherical harmonics function. By considering the shadowed diffuse transfer simultaneously, the soft shadow of diffuse objects was generated successfully under dynamic, low-frequency lighting environments. The experiment results showed that this algorithm approached accurately with high quality.
Abstract:Wide-band signal processing is one of the topics in electronic warfare. In contrast to narrowband signal processing, wideband signal processing can result in the worsening of digital range，sensitivity and multiple signals processing，etc. To tackle these problems，this paper introduces some modern advanced electron technologies，including wideband sampling，array processing，digital channelizing，and jamming based on the digital radio frequency memory etc. in wideband digital signal processing，and analyses the effects of bandwidth on these technologies. It discusses the applications and the development trends of the technologies in electronic warfare. It is expected that the topic could provide useful reference for engineers engaging in the digital signal processing.
Abstract:Noise power spectrum estimation is a fundamental component of speech enhancement. An improved weighted noise power estimation algorithm is proposed in the paper by taking into account the correlation of inter-frequency in the noisy speech. Because of calculating the weighting factor from the time domain and frequency domain smoothed noisy speech, the new presented algorithm can distinguish noise and weak speech more accurately, especially in the weak speech regions following strong speech. The tracking delay and the overestimates are all considerably reduced compared to competitive noise tracking algorithms. Objective experimental results and a subjective comparison show that the improved noise estimation algorithm is preferred to other noise estimation algorithms when integrated in speech enhancement.
Abstract:An approach for intra-pulse feature extraction of radar emitter signals was proposed based on the multi-resolution characteristics of wavelet transform. It was efficient to obtain quantitative information from signals. The energy entropy from approximation coefficients of wavelet transform and the other energy entropy from inter-scale correlations denoise of detail coefficients were adopted together as two-dimensional feature vectors. Experiment results demonstrated that the features of ten typical radar emitter signals extracted by wavelet transform showed good performance of noise-resistance and clustering when Signal-Noise Ratio(SNR) was low.
Abstract:This paper introduces a power driving circuit for Laser Diode(LD). It adopts power Metal- Oxide Semiconductor Field Effect Transistor(MOSFET) as adjust device，and apply current negative feedback to ensure constant current output. The output current is a forward current adjustable in 0 A–10 A range with ripple less than 10 mV，whose short-term stability has reached 1×10-5. This circuit also bears functions including maximum current，surge current limitation and slow start. It has been applied as pump source for a Yb doped optic fiber laser，and the experimental results has proved its reliability and safety.
Abstract:Microwave Positive Intrinsic Negative(PIN) switch speed and power capacity are two contradictory parameters. In order to improve the two parameters at the same time，combining the characteristics of semiconductor，this study adopted the design of PIN diode feeding simultaneously (namely double-fed switch). By optimized design，Single Pole Double Throw(SPDT) PIN diode switch from 2 GHz~6 GHz was obtained. Its switch speed and power capacity were improved greatly in comparison with traditional switch circuit. This study has laid a good foundation for successive engineering application.
Abstract:Aiming at the echo problem in communication, this study designed an adaptive echo cancellation with the algorithm of Least Mean Square(LMS). By using of DSP Builder Tool combining Matlab/Simulink and Quartus II design tools, the hardware circuit of this canceller was implemented in FPGA chips with the concepts of modularization. Software simulation of modules was conducted and hardware verification of the whole system was completed. The results proved the correctness of the design. This design makes the implementation of the adaptive echo canceller simpler and faster.
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 structure of FIR filter determines that it will consume a great deal of the resources of flip-flop or memory to design the FIR(Finite Impulse Response) filter by using the FPGA(Field Programmable Gate Array). Taking the n-order filters for example, a method of read and write operations to save the resources of flip-flop and dual-port RAM was presented. Comparing with a conventional FIR filter, the application simulation in a communication system showed that the method was not only good for filtering, but also in reducing a number of adders and multipliers, saving flip-flop and dual-port RAM effectively. The higher orders of filter, the more resources were saved.
Abstract:Based on the wireless communication performance of Unmanned Aerial Vehicle(UAV) airborne Synthetic Aperture Radar(SAR), the design of ground terminal system for UAV airborne SAR is presented in this paper. The key techniques applied in the system are described in detail, and a deep research on Directdraw, double buffering, multithreading and memory mapping techniques is performed as well. Application result proves that the design has realized time reasonable assignment between image process and data receiving. This study will be of great value for designing of ground terminal system for UAV airborne SAR.
Abstract:To defend network system against the harm done by unauthorized access. basing on theory and conception of trusted computing and Role Based Access Control(RBAC) model，this paper proposes an access control model named Environment Role Based Access Control(ERBAC). This model correlates the role with system environment security. When an user′s environment is secure enough, the permissions corresponding to its roles are valid，and the user is allowed to access resources. An access control application instance is given to prove the effectiveness of the model and semantics.
Abstract:In order to implement communication between System On Chip(SOC) and peripheral device，an interface design for data transfer between Advanced Peripheral Bus(APB) and Inter-Integrated Circuit(I2C) has been proposed in this article. It first describes the function partition of the whole system. Then the APB interface design and register configuration are introduced. The design of main state-machine of I2C bus and the implementation of clock generator are presented. Asynchronous First In First Out(FIFO) is adopted to synchronize data transfer between APB bus and I2C bus. Finally，the functional simulation has shown that the design performs well in both 100 kbps and 400 kbps. It completely meets the requirement for transfer speed.
Abstract:To meet the requirements of the robot driver for automobile emission durability test，a multi-sensor data-acquisition system was designed. The reliability and real-time performance of data acquisition were improved. The hardware system consisted of sensors，conditioning circuits and a data-acquisition card ACL8112，while the software system consisted of the card driver on Linux and performance functions. The main floor data were sampled during robot driver’s working. It is shown that the system works reliably in the sampling period of 20 ms.
Abstract:The programming of database and report in LabVIEW is a difficult problem for the engineers who use LabVIEW to develop test&control system software. The database programming technique with the third part database tool in LabVIEW is introduced in detail. The hybrid programming technique of report with LabVIEW and Delphi is also discussed. With the hybrid programming technique，the report can be created easily and conveniently in normal and diversified types. The project application has indicated that most test&control system problems about database and report programming will be tackled with these techniques and will get satisfying results.
Abstract:This study introduced the realization of a new monitor-controlling instrument of turbine protection system based on high performance DSP TMS320F2812. The signal of turbine measured by sensor was processed effectively by DSP or judged logically, then the result was outputted to PC, executive body or other instruments, in order to monitor and control the turbine. The protection system with this instrument is provided with many advantages, such as small volume, quick processing and high accuracy. Particularly, a few instruments can be collected by enhanced Control Area Network(eCAN) bus for realization of distributed real-time control.
Abstract:Dynamic Power Management(DPM) is a design methodology aiming at reducing power consumption of electronic systems by performing selective shutdown of idle system resources. How to improve predictive accuracy is the main problem needed to be solved in DPM policy based prediction. With the assumption of the relevancy among the pieces of idle time，the exponential average policy Under is prevalently used can not predict accurately when abnormal error like a sudden long or short idle period happens. In this paper, the authors propose a new adaptive DPM predictive policy basing on improved exponential average model and mathematic definition of abnormal error. The policy would self-adjust to get higher predictive accuracy if sudden error occurs. The new policy excels the existed ones in prediction accuracy.
Abstract:Based on the anterior knowledge model, a Dynamic Spectrum Access(DSA) algorithm was proposed according to the Channel Remaining Idle Time(CRIT) estimation. Each Secondary User(SU) maintained an estimation vector of the CRIT and upgraded it periodically. At the beginning of each time slot, SU chose a channel with the largest CRIT estimation to access. The adaptability of the DSA algorithm was analyzed and the optimal transmission time for the SU was obtained. Simulation results show that the new algorithm has 5%-10% higher channel utilization efficiency than other ones under certain channel parameters while making the lowest interference to Primary Users(PU).
Abstract:Aimed at the scalability of resource allocation preferring for system performance，the advantages of economic-based mechanisms for resource management in grid computing was addressed. The model and the algorithms based on pricing mechanism and Nash equilibrium were analyzed. After comparing the representative works related to economic-based grid resource scheduling，this study pointed out the significant problems existing in this field and prospected the research orientations of economic dispatch control.