Abstract:Considering the defection of general compression algorithms which neglect the characteristics of Synthetic Aperture Radar(SAR) images, an adaptive compression algorithm based on the distribution of ocean-SAR images was proposed. According to the distribution, a quantization strategy was employed, through which target and background were retained respectively. Using the sparsity of the scene, pixels above the threshold were mapped to a triple before entropy encoding for both grayscales and locations. Then Bit Plane Encoder(BPE) was employed considering the relatively small deviation of the remaining background. Experimental results showed that the Peak Signal Noise Ratio(PSNR) of proposed algorithm was 5 dB-10 dB higher than JPEG2000 at the same bit rates. The proposed algorithm, with better contrast and lower computational complexity, is well suited to various requirements of ocean-SAR image compression.
Abstract:An Extended Kalman Filtering algorithm of autonomous orbit determination is presented in this paper. This algorithm can determine the satellite position and velocity vectors using cross-link range information. The STK satellite software developed by the AGI Company is used to create the GPS constellation scene，and cross-link range is derived based on quasi-distance among GPS satellites．Peak value of error is decreased by using the value of Geometric Dilution Of Precision(GDOP) to replace reference satellite. The simulation results demonstrate that the precision of orbit determination is greatly improved.
Abstract:In radar system, one of the most important direction of research is how to improve the accuracy of target tracking. In this study, a new algorithm, Sequential Block Kalman Filter(SBKF), was proposed based on the traditional radar tracking model, from the perspective of batch process. This algorithm jointed different state vectors together and modified the measurement equation to improve the track accuracy. It is proved by simulation that SBKF is superior in filtering precision and convergence to traditional Extended Kalman Filter(EKF). This new algorithm can obtain more stable results, and can also suppress the effect of nonlinear measurement equation and the wild value.
Abstract:P-code is chiefly applied to precise positioning service presently，which has a higher tolerance to jamming and spoofing compared to C/A code. Meanwhile，the acquisition of the weak signal in complicated environment requires higher sensitivity and shorter time. This paper proposes the improvement method of Fast Fourier Transform(FFT)-based acquisition searching in both frequency domain and PRN code phase domain—overlap average method. The algorithm has been validated by Matlab simulation and implemented in Field Programmable Gate Array(FPGA) by certain design. It can improve the hardware efficiency and decrease the acquisition time.
Abstract:A method for navigation signals down sampling was presented in this study by combining RF direct sampling and digital down conversion. An analysis of navigation signals at frequencies that close to 1.2 GHz and 1.5 GHz was performed. Firstly, bandpass sampling principle was used to select appropriate sampling frequency for the completion of RF direct sampling to navigation signals. Then cascaded integrator comb filter and Half-Band(HB) filter were adopted to carry out decimation filter to the sampled signals, thus realizing the purpose of reducing sampling frequency. Finally, the navigation signals of 5 frequencies were simulated in Matlab, RF direct sampling of the navigation signals was accomplished and the sampling frequency was reduced. The original navigation signal was recovered and separated. It proves the methods of RF direct sampling and digital down conversion are feasible.
Abstract:In the design of wide-band Marchand Balun，the three-conductor coupled lines which replace the two-conductor coupled lines were adopted to broaden the bandwidth and enhance the coupling factor. The capacitance，inductance compensation and impedance network were utilized to improve port match performance. Simulation results show that the port match，output balance and phase differences have been improved．Between the bandwidth from 20 GHz to 55 GHz，S22,S33 are both smaller than -15 dB, while S23,S21 are smaller than -10 dB and -3.6 dB respectively. The amplitude difference is about 0.1 dB.
Abstract:The Rotating-element Electric field Vector(REV) method, for far field calibration of Phased Array Antenna(PAA)，was proposed in this study. First，a 4×4 two-dimensional PAA was commendably calibrated at 0° scanning angle for using REV method by HFSS. Then，a method combining maximum method was used in wide scanning angle calibration with CST，which showed good effect. At last，a test was carried out. The results indicate that the method is valid for small PPA in wide scanning angle.
Abstract:This paper presents a fast and efficient way to extract the target text areas. First, the edge detection and mathematical morphology are used to realize coarse location of text and graphic areas. Then several window features are extracted to distinguish the text areas from graphic areas and thereafter certain rules are set to extract the target text areas. The algorithm has high location accuracy and low time complexity due to weakening the interference of background areas. At the same time, OSTU algorithm is applied to enhance the adaptability of images with complex background during binarization. Test results on several types of samples indicate that the algorithm has strong popularity. The high accuracy of the method has also proved the validity of the algorithm.
Abstract:Solar power is now the new energy which has huge development prospects，the advanced and efficient solar cell producing industry has great significance for solar power，so solar cells defect detection technology in the process of producing solar cell has huge application value. The new technology of using near-infrared imaging for solar cells defect detection shows high efficiency，however，the current industry only uses a relatively simple post-processing. Based on the near-infrared images of solar cell for some image processing，the defects of solar cells，such as debris，cracks，broken gate，etc.，can be identified more quickly. Compared with the traditional methods，this new method can identify more detection fault types with higher efficiency，therefore can significantly reduce the failure in the production of solar cell.
Abstract:Practical signals such as radio transient signals turn out to be non-stationary and nonlinear time series, and estimating instantaneous parameters of such signals in time domain will benefit detecting and identifying specific emitters, such as radio stations and aerospace targets. However, conventional methods such as wavelet and Wigner-Ville distribution(WVD) methods are difficult to deal with these transient signals when the signal is not stationary. To provide more efficient approach for estimating instantaneous parameters of non-stationary and Specific Emitter Identification(SEI) with high accuracy, a method based on Intrinsic Time-scale Decomposition(ITD) for analytic signal is proposed in this paper. The simulation results are presented to demonstrate the effectiveness of this novel method.
Abstract:Present track association algorithms in distributed multi-target passive tracking system always adopt theory in multi-sensor information fusion, in other words, only state informations of targets are concerned. A new track association algorithm is proposed based on information fusion of multi-feature such as frequency pulse-width and Pulse Repetition Interval(PRI) in distributed multi-target passive tracking system by applying Dempster-Shafer(D-S) evidence theory. The algorithm is of such advantages like faster association speed, higher correctness probability and it can be adapted to circumstance of dense targets due to the use of multi-feature information. The simulation proves that the proposed algorithm is superior to weighted track association.
Abstract:The channel noise variance information is required by the soft decision for a channel decoder. However, such information is usually unknown and/or time varying. In this paper, the effects of channel noise variance on soft decision metric are analyzed. Then, a new channel noise variance estimation method applied to the multipath fading channel is presented to generate exact soft-decision metric for a channel decoder. Applying the proposed method to the outer receiver of Digital Terrestrial Multimedia Broadcasting(DTMB) system, simulation results indicate that the proposed method converges rapidly and the generated soft decision metric is very close to the optimal one.
Abstract:Based on Affine Projection Algorithm with Selective Regressors(SR-APA)，a new algorithm is proposed with a view to data reusing factor. The proposed algorithm introduces a weighting method to change the selective principles. Unweighted original data is reused in the iteration to avoid increasing the condition number of the input data, and finally the steady state Mean Square Error(MSE) is reduced. Simulation results show that the proposed algorithm not only reaches lower steady state MSE than SR-APA, but also accelerates the convergence speed of SR-APA. And with the same performance，the proposed algorithm has only 50% computations of SR-APA.
Abstract:Multi-carrier transmission has been employed widely for communications and jamming system. But high Peak to Average Power Ratio(PAPR) of the transmitted signal is a major drawback of multi-carrier transmission system. This paper introduces the definition of PAPR and some main methods of PAPR reduction. In order to reduce the large computation complexity of traditional methods and keep the invariability of spectrum，a real-time PAPR reduction algorithm based on Field Programmable Gate Array(FPGA) has been proposed. This method improves the traditional phasing algorithm and has been implemented in Virtex-5 chip of XILINX. The experiment results show that the proposed method can reduce the PAPR with low complexity，and thus is of good practicability.
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: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:A high performance packet detector for MB-OFDM UWB(Multiband Orthogonal Frequency- Division Multiplexing Ultra Wideband) system is proposed according to MB-OFDM UWB physical international standard ECMA-368. On the basis of conventional cross correlation，the detector can complete packet detection and fine symbol timing at the same time by accumulating multi-path energy. Simulation results show that the new detector has a lower packet detect error rate and a higher symbol timing precision compared with the existing schemes.
Abstract:Radio broadcast signal monitoring is an important guarantee for the safety of broadcasting. A systematic solution to process digital signal based on FPGA platform is presented，aiming for the audio remote and local monitoring. Specially addressed in the paper includes audio signal acquisition，analysis， switching，network transmission modules and software designs. Also，the picture of actual object and test results are given. Test shows that the system is reliable and of stable performance，greatly reducing the burden of the radio listener in the broadcast station.
Abstract:According to the early research of the relationship among the capability of vanadium batteries and various environmental parameters，the runtime parameters of vanadium, an intelligent monitor and manage system for vanadium batteries was designed. The data gathering, analyzing and control functions of the system were implemented by using a Micro Control Unit(MCU) as a controller，and LTC6802 was adopted to gather multi-channel voltage in serial. Data exchanging between the MCU and the monitor host computer was realized by ethernet. Through this system，the researchers can quickly obtain more full and accurate data of vanadium batteries in its R&D stage，therefore quicken the progress of the research and application of vanadium batteries.
Abstract:This paper discusses Fault Tree Analysis(FTA) technology, uses FTA to analyze a variety of software elements causing software system failure, and constructs software system fault tree through determining all software failure combination of reasons. Then generates the minimum cut sets of fault tree，analyses the security constraint conditions of cut sets，and analyzes the testing data according to the security constraint conditions. Thereafter, the testing case algorithm is generated．Practice shows the fault tree analysis technique can be used to guide the design of software testing, reflecting the systematic, accuracy and predictability of systems engineering methods to study software testing.
Abstract:To achieve Image-Based Visual Servoing(IBVS) for mobile robots more easily，and avoid using an approximate input-output linear feedback which has many assumptions，three methods combining epipolar geometry with triangle geometry were proposed. The proposed approaches did not need any knowledge of 3-D scene geometry. Simulation results validate the effectiveness of the proposed approach.
Abstract:The Internet Of Things(IOT) is to make full use of next generation IT technologies among the industries，and the technologies of Radio Frequency Identification(RFID) and Wireless Local Area Network(WLAN) are an important part of IOT. This paper describes the principles and network structures of RFID and WLAN technologies，and studies the system solutions of the joint application of them，then analyzes an application instance. Finally，this paper outlooks their market prospects. Analysis shows that，RFID and WLAN joint application，making the most of the characteristics of WLAN and RFID，can provide users with faster，and more flexible identification services，and has broad market prospects.
Abstract:It is one of the key issues that making knowledge discovery effectively in a Cognitive Radio(CR) engine design. Basing on the research about Rough Set Theory and C4.5 algorithm of decision tree, this study presented a model of CR knowledge discovery designed by combination of rough set and decision methods and studied its feasibility through a case. Using data based on simulation platform of MATLAB 802.11a physical layer as CR perception sample, decision tree sequence was trained, and decision tree was built for knowledge extraction. Then the accuracy and performance of the design model was evaluated by confusion matrix. The simulation results show that the proposed design model gets high classification accuracy rate, can enhance the interpretability of knowledge，and therefore has preliminarily achieved the purpose of knowledge discovery for cognitive radio and learning from the experiences.
Abstract:This research built a flight phase safety risk assessment model basing on Back Propagation(BP) neural network. By using MATLAB software and flight data of A320，the training and verification of the model were realized，and the errors were acceptable. The results shows that the model is capable of predicting the possible risk in a flight phase. Moreover，the flight phase safety risk assessment system can provide scientific solutions and can be taken as a tool, which facilitates not only the management regarding flight safety for an airline company，but also the role in flight supervision for the civil aviation administration.
Abstract:Based on the mechanism of magnetorheological finishing by computer control for optical surface, the core issues of process software are calculating dwell function and designing of machining path. This study utilized Jansson-Van Cittert algorithm to calculate dwell function，then optimized machining path. It accomplished software modularization programming, modular testing and integration testing. Finally, a validity and reliability test on a fused silicon element with an aperture of 330 mm×330 mm was performed. The data were consistent between analog surface and practical polishing surface. This proves that the software can control the whole magnetorheological finishing process accurately and effectively.
Abstract:It is significant to explore the Multi-access(MAC) protocol of HF due to the poor bandwidth of HF. In this study，the protocol of Multi-access for 3G-Automatic Link Establishment(ALE) was researched. Then based on OPNET Modeler, the networks model, node model and process model of the 3G-High Frequency(HF) were designed. The process of automatic link establishment was simulated. Simulations for successful ratio of link establishment were executed under different conditions. The results show that the Bit Error Rate(BER) has the most important effect on the ratio，while the number of channels and network nodes are following, and the traffic of nodes has the least impact.