Abstract:Active jamming was one of the most important menaces for radars, and the radar detection range was the groundwork for evaluation of anti-jamming. Based on the analysis of theoretical computation and practical anti-jamming measures, a modified mathematical model for calculating the radar detection range in jamming environment was proposed. The simplified model only needed the calculation of a few modification coefficients, so it was convenient for application. The model could also explain the dynamic change of radar detection range under different anti-jamming measures, thus it was helpful for the evaluation and improvement of the anti-jamming performance. The simulations showed validity of the modified model.
Abstract:Parallel encoders are often used in fiber communication networks. This study introduced an automatic generation method for parallel Reed-Solomon(RS) code encoder Intellectual Property(IP) based on the automatic searching for datapath in parallel computation and auto-generation of the Gaolis computation circuit. The uniform structure made its HDL codes easily generated by software. The synthesis result of the designed 9*parallel RS(255,223) encoder showed that with gate-level optimization, this automatic implementation used less resources, and maintained the same working frequency with the original circuit.
Abstract:Digital Compass is a kind of device which can acquire the carrier’s attitude. This study introduced the principle of an electronic compass. By using magneto resistive sensor chip HMC1022 made by Honeywell，a 2-axis electronic compass was developed. The amplifier AD623 was used as the signal conditioning circuit. The MPU MSP430 was in charge of A/D converting, azimuth computing and digital outputting. And the Set/Reset(S/R) circuit was adopted so that the error due to null and drift could be minimized. Experiment results showed that the system had good ability to acquire the carrier’s attitude with stable operation and low power consumption. The error was below 1°.
Abstract:By studying the key technologies of Joint Tactical Information Distribution System(JTIDS)，and utilizing Simulink software，this study realized the source error control coding. By using 32 bit Cyclic Code Shift Keying(CCSK) code-word S0 to establish spread spectrum space, the tamed spread spectrum was completed. The random transformation of 51 frequency points was achieved with VCO module and the link simulation of JTIDS was prosecuted. The anti-jamming performance of this system was analyzed in the Additive White Gaussian Noise(AWGN) channel and jamming environment，which laid the foundation for the study of effective jamming to this system.
Abstract:Power bus noise problem and Electromagnetic interference(EMI) problem caused by resonant impedance had become a major concern for Electromagnetic Compatibility(EMC) engineers engaged in Printed Circuit Board(PCB) design. Previous research had shown that proper Electromagnetic Band-Gap(EBG) structure could reduce not only the magnitude of the transfer impedances but also the number of the resonance peaks, thus contributed to the EMI reduction of the power bus. In this paper, we had focused on the EMI problem from the power bus structure using such EBG structures and found that using the magnetic material coating on the power and ground planes could significantly contribute to the EMI reduction.
Abstract:Formulation and solution of the Vector Radiative Transfer(SVRT) equation in a finite slab of stochastic precipitation medium composed of two different rain rates were considered. Computer simulation was given to verify the obtained results via Monte Carlo method, to feature the distinctiveness of the stochastic precipitation medium, and to illustrate the influences of the stochastic parameters imposing on the final results. The relationship between an average-rain rate precipitation layer and a stochastic precipitation medium was also discussed.
Abstract:A wideband, minitype and analog optical fiber system was designed for measuring instantaneous electric field produced by nuclear burst with a strong electromagnetic interference. In the system, a monopole antenna was used to convert electric field into voltage, at the same time a minitype transmitter converted voltage into optical signal, and the optical signal was send to the receiver which was far away from transmitter by the optical fiber, finally the voltage was received at the receiver. The system was of good performance, with bandwidth 24 kHz~1 000 MHz, noise smaller than 12 mV.
Abstract:The importance of millimeter wave frequency synthesizers was introduced briefly, the advantage and disadvantage of two schemes of millimeter wave frequency synthesizers were analyzed, and a design scheme of millimeter wave frequency synthesizers was put forward by the combination of their merits and the Direct Digital Synthesis(DDS) technology. A systematic experiment of the scheme was operated, and the results showed that the phase noise was -85dBc/Hz@10kHz. so the performances of the whole millimeter wave communication system were improved.
Abstract:The induced current law on transmission line was studied in electromagnetic pulsed environment. And the variety law including induced current、load voltage、the power were researched according to the following situations: one terminal in short-circuit state and another terminal linked with resistance; two terminals connected with different resistances respectively. The way of non-contact pulsed current injection was taken on the experiment, and the theoretical analysis were done with the transmission line theory model. The results of both ways were identical rule. The results indicated that in electromagnetic pulsed environment the induced current on transmission line and the voltage on the end port resistance had direct relationships with value of load. The dissipative energy by the resistance would reach the maximum value when special resistance values were selected.
Abstract:The ensemble of the cavity scattering matrix and the corresponding radiation scattering matrix were obtained within the computer-box cavity. For a given Loss-Case cavity，normalized impedance and normalized admittance were obtained by random matrix theory. Dyson’s circular ensemble proved the existence of wave-chaotic in the cavity. The good agreements between the experimentally observed values and the Random Matrix Theory results were achieved for the normalized impedance, which indicated the prediction function of random matrix theory on wave chaotic systems. There was a good agreement between the statistic properties of normalized impedance and normalized admittance obtained in experiments，which testified that these two physical quantities were unaffected by the coupling of systems.
Abstract:In order to assess pulse wave shielding effectiveness of shielding room from the traditional Continuous Wave(CW) test results，a frequency response function method was proposed. Taking the measurement of shielding effectiveness for pulsed magnetic field as an example，experiments and analysis were carried out to verify the effects of the above-mentioned approach. The result showed that the estimated pulse inside shielding enclosure was close to the real measured waveforms. This technology provides an effective mean for the conversion of CW measurement results to pulsed field shielding effectiveness.
Abstract:The Energy doubler for HPM pulse compression was developed to implement miniaturized source of high power microwave. Using the Phase Shift Keying(PSK) switch, output power, which was higher than input power, could be obtained. It could output 35 MW when the input of peak power was 5.3 MW. The power gain could reach 7dB. In order to obtain the straight top waveform, some researches were done on the technology of PM–AM. These results can satisfy the requirements of miniaturized sources of high power microwave in different experiments.
Abstract:A new reversible data hiding technique based on difference expansion was proposed. Its main idea was that some difference values which were outside the interval defined by the threshold T were shifted into the interval. A location map was created for the difference inside this interval. The proposed method could not only achieve high embedding capacity but also have smaller location map than other methods. The method was more effective especially while the threshold was small. Experiment results showed that our proposed method had better performances than other methods in terms of high embedding capacity and low distortion.
Abstract:Driver Developer’s Kit(DDK) has provided a set of standard DSP/BIOS device driver model, based on which, the process of the video driver development can be shorten and the codes’ compatibility and portability can be increased. Taking the TMS320DM642 video special board for example, the method of video driver’s development and the process based on DDK were discussed in detail. The debugging result was given for the example. It has been proved that development of video driver based on DDK can work steadily for the video application.
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:Aiming at reducing the large amount of computation of Sub Space Decomposition(SSD) algorithm and improving the poor precision(when signal to noise ratio is below 0 dB) of the Maximum Likelihood Estimation(MLE) algorithm to estimate the signal to noise ratio of the Continuous Phase Modulation(CPM) signal，a new fast algorithm with higher accuracy is presented in this paper. This new algorithm is an improvement based on the frequently used MLE method. It takes the statistic and cross-correlation of the received signal into account, and can estimate the SNR fast and precisely without the initial phase. Error estimate is less than 1 dB when RSN is between -20 dB and 20 dB. A comprehensive deduction of the algorithm is included in this paper. Simulations by MATLAB and FPGA implementation show the validity of this algorithm.
Abstract:A novel approach combining Decision Directed(DD) estimation and Predicted(PD) estimation was proposed to improve the priori Signal to Noise Ratio(SNR) estimation for speech enhancement in noisy environments. PD estimation incorporated the soft-decision scheme and speech presence uncertainty. In contrast to the conventional DD-based scheme, a less speech distortion was achieved when a posteriori SNR was higher; while a further reduction of musical noise was achieved when a posteriori SNR was lower. It was also found that a special case of the proposed method had been degenerated to the DD estimation with a weighting factor. Experimental results demonstrated the improved performance of the proposed algorithm.
Abstract:A steganalysis algorithm based on statistical characteristics of DCT(Discrete Cosine Transform) coefficients for JPEG(Joint Photographic Experts Group) image was proposed. The algorithm analyzes statistical characteristics of DCT coefficients, calculates a total of 8 dimensional feature vectors from each JPEG image, and using LS-SVM(Least Squares Support Vector Machines) classifier to classify cover and stego images, which can apply to blind steganalysis. The algorithm can be implemented conveniently and computed easily. The experiments results show that, the algorithm has good performance in both detection rate and computation speed, and it is also reliable to steganalysis for all kinds of JPEG images steganography.
Abstract:The dose rate effects of anti-fuse FPGA was specifically studied for parts screening. The results of experiments showed that all of the test circuits were seriously disrupted by low level of transient γ radiation, but none of them had latch up effect in high level of radiation. The low level radiation damage was due to that the transient photocurrents had caused the disruption of logic functions of anti-fuse FPGA. Nevertheless, the resistance of programmable switches in sea-cells prevented the radiation induced latch up effect in anti-fuse FPGA. The study results showed that the circuits hardening design was the best method to increase radiation fault-tolerance of anti-fuse FPGA.
Abstract:Radiation hardened packages were prepared by using special composite shielding material and welding technique. Hardened package memory LS28C256R which was based on general package memory 28C256 was produced. Special experimental testing circuit and testing software were designed to dynamic test memory devices using linear electron accelerator. The result of contrastive irradiation test indicated that the performance of the hardened package memory LS28C256 in anti-electron irradiation was 1~2 orders of magnitude better than the general package memory. This hardened package method had provided technical support for the space application of COTS(Commercial Off-The-shelf) devices.
Abstract:Improving Single Event Upset(SEU) resistance of Static Random Access Memory(SRAM) is being a hotspot in the research area of electronics Radiation-Hardening. It is hard to improve the anti-SEU ability of bulk CMOS SRAMs without circuit Radiation-Hardening，whereas more area and power consumption will be spent with Radiation-Harding design. To investigate the SEU resistance of Silicon on Insulator(SOI) SRAMs，this study introduced the key technology breakthrough in SOI CMOS Radiation- Hardening process and 128 kb SRAM circuit design. The SEU experiment of a homemade 128 kb SOI SRAM showed that its threshold Linear Energy Transfer(LET) value was more than 61.8 MeV/(mg/cm2)，which was higher than that of CMOS SRAMs without Radiation-Hardening design. It is concluded that SOI fabrication process is promising to obtain preferable SEU resistance of SRAMs with proper considerations on basic device and 6-T cell structure.
Abstract:Position Sensitive Detector(PSD) features high position resolution and the setup of position displacement measurement system is simplified. The performance of measurement circuit is the key factor for the application of PSD. Some results are obtained by the way of analyzing the equivalent noise of measurement circuit. The circuit noise is one of the most important factors which will lower the position resolution. For one dimensional PSD device S3932, the position resolution of 1μm can be achieved if the photocurrent of the device is above 7μA.
Abstract:A magnetic analyzer was designed to measure the energy spectrum of the pulsed intense electron beam of a linear induction accelerator. The principle of magnetic analyzer was described. The basic parameters were set based on the accelerator and some test conditions. The magnet was designed theoretically according to these parameters. 3-D simulation and optimization of this design were performed using Opera/Tosca software from Vector Fields Co. The final parameters of this magnetic analyzer were obtained. The magnetic analyzer was C-shape, with the bending radius of 300 mm and the bending angle of 60 degree after hard-edge approximation, and the good-field-region was 6.54 cm. Results of the design satisfy the physical requirement very well.
Abstract:As the IC feature size continues to decrease, interconnect cross-talk noise with the process fluctuation is also a corresponding increase in sensitivity. The impact of interconnect process fluctuation on the interconnect cross-talk noise in Very Large Scale Integration(VLSI) was studied and discussed in this study. The approximate function relationships were obtained by analyzing the impact of interconnect geometric parameters fluctuation on the interconnect parasitic parameters. On the basis of these studies, the statistical cross-talk noise model was successfully proposed and built. The expressions of mean and standard deviation of interconnect cross-talk noise could be obtained from this model. Compared with HSPICE, the computation results showed that the time of calculation was greatly shortened with a good calculating precision using the proposed method. It will have a potential bright future in the analysis and optimization of VLSI interconnects signal integrity.
Abstract:In beams automatic alignment system，by adjusting the angles of many cavity mirrors and reflectors of laser equipment，the direction and position of beam can meet to the physical criterions. To increase the collimation efficiency of far and near field and reduce the adjustment times for motor，this study proposed a collimation arithmetic. Adjustment arithmetic of round image was implemented in the collimation of cavity mirror. In the collimation of reflector，correlative coefficient matrix was improved from traditional two dimensions to four. By the alignment experiment platform，the arithmetic was proved to be converged rapidly. The adjustment steps of motor were more accurate，and the times of move were less than three，which could meet the collimation precision requirement.
Abstract:The design requirements of the control system for a Linear Induction Accelerator(LIA) are presented, as well as the hardware and software configuration of this system. The feature of PXI bus and the design of a DAQ/Control based on PXI are described on emphasis. Combining PXI with embedded system, the structure of LIA control system can be simplified and the performance can be improved. Relative equipments can be controlled and integrated by CVI programming. The final product has been successfully tested in the Linear Induction Accelerator.
Abstract:In order to solve the problem of the existing anti-theft device easily to be cracked and reproduced when communicating at a fixed-frequency, a new anti-theft device was designed on nRF905 which had the function of frequency modulation. Since the communication frequency was kept changing， the information could not be interfered or intercepted，and the anti-theft device was difficult to be reproduced and cracked．Through the communications program optimization and program design, the reliability of the frequency-hopping communications was improved. The car owner could gain prompt access to car conditions and alarm information through the two-way communication function. The multi-sensor detection circuit design could improve the reliability of the anti-theft device. The new anti-theft device has been tested to have a good effect，so it has good prospects of application.