Analysis on two novel spherical helical antennas

Two novel spherical helical antennas are designed by projecting the planar equiangular spiral antenna onto hemisphere and partial sphere surfaces. Their radiation properties are analyzed by the moment method with curved basis and test function, and the curves of the voltage standing wave ratio (VSWR), gain, polarization and pattern that change with frequency are also given, respectively. It can be seen that the circular polarization band of the novel hemispherical helical antenna is broader. The gain curve of the partial spherical helical antenna is flatter and the structure is simpler. __________ Translated from Journal of Xidian University, 2008, 35(1): 144–147 [译自: 西安电子科技大学学报 (自然科学版)]     

Observational linearization and tracking objective excitation control strategy based on phasor measurement unit

To improve the transient stability of multimachine power systems, observational linearization and tracking objective excitation control laws were derived from the phasor measurement unit (PMU), observational linearization, and tracking objective control theory based on synchronized coordinates and reference generator coordinates. The control strategies utilized real-time state variables obtained by PMU to linearize the state equations of the system, and then the linear optimal control strategy was used to design excitation controllers. The inaccuracy of the local linearization method and the complexity of the system models designed in the exact linearization method for nonlinear systems were avoided. Therefore, the control strategies were applied in real time. Simulation results show that the proposed method can improve the transient stability of power systems more efficiently than nonlinear optimal excitation control. Translated from Journal of Sichuan University, 2006, 38(2): 146–150 [译自: 四川大学学报 (工程科学版)]     

Design and implementation of a multi-axis precision movement machine based on MAS theory

A model construction of a multi-agent system (MAS) and the basic function of the agent are described. The precision control method using the multi-CPU of a programmable logic controller (PLC) is introduced, and a distributed method using multiple CPUs to control different motion machines is given. The test results indicate that in industrial control fields, the combination of using the credible PLC to control the motion machine and multi-CPU task distributing methods can solve multiaxis machine linkage and implication, providing a more credible method for multi-axis motion units. __________ Translated from Journal of North University of China (Natural Science Edition), 2007, 28(1): 32–37 [译自:中北大学学报(自然科学版)]     

Robust controller for a class of uncertain switched fuzzy systems

A robustness control of uncertain switched fuzzy systems is presented. Using the switching technique and the Lyapunov function method, a continuous state feedback controller is built to ensure that for all allowable uncertainties the relevant closed-loop system is asymptotically stable. Furthermore, a switching strategy that achieves system global asymptotic stability of the uncertain switched fuzzy system is given. In this model, each subsystem of the switched system is an uncertain fuzzy system, and a common parallel distributed compensation controller is presented. The main condition is given in the form of convex combinations which are more solvable. This method transforms a certain switched system and has strong robustness for various system parameters. Simulations show the feasibility and the effectiveness of this method. Translated from Journal of Northeastern University, 2006, 27(7): 713–715 [译自: 东北大学学报 (自然科学版)]     

A novel MEMS-based focal plane array for infrared imaging

On the basis of opto-mechanical effect and micro electromechanical system (MEMS) technology, a novel substrate-free focal plane array (FPA) with the thermal isolated structure for uncooled infrared imaging is developed, even as alternate evaporated Au on SiN cantilever is used for thermal isolation. A human thermal image is obtained successfully by using the infrared imaging system composed of the FPA and optical detecting system. The experiment results show that the realization of thermal isolation structure in substrate-free FPA increases the temperature rise of the deflecting leg effectively, whereas the noise equivalent temperature difference (NETD) is about 200 mK. Translated from Chinese Journal of Semiconductors, 2006, 27(1): 150–155 [译自: 半导体学报]     

A new TDOA algorithm based on Taylor series expansion in cellular networks

Time difference of arrival (TDOA) is the positioning technique with the most potential in cellular mobile telecommunication systems. The Taylor series expansion method has been widely used in solving nonlinear equations for its high accuracy and good robustness. However, the performance of the Taylor’s method depends highly on the initial estimation. Therefore, one new algorithm, hybrid optimizing algorithm (HOA) was proposed, which combines the Taylor series expansion method with the steepest decent method. The steepest decent method features fast convergence at the initial iteration and small computation complexity. HOA takes great advantage of both methods. Simulation results show that HOA achieves better performance on positioning accuracy and efficiency. __________ Translated from Journal on Communications, 2007, 28(6): 7–11 [译自: 通信学报]     

Common-mode radiation characteristic analysis of connections between cables and metal cases

In this paper, the common-mode radiation characteristic of the connection between a cable and a conductor is analyzed by the electric field integral function (EFIF) and the method of moment (MoM). The RWG basis function is adopted as the conductor basis function, the pulse basis function as the wire basis function and the juncture employs Costa basis function. A scheme of singular region separation is proposed to overcome the integration singularity of juncture matrix elements. Some new conclusions of the common-mode radiation characteristics with the metal case are obtained by numeration. __________ Translated from Chinese Journal of Radio Science, 2007, 22(3): 375–379 [译自: 电波科学学报]     

Multi-scale Kalman filters algorithm for GPS common-view observation data based on correlation structure of discrete wavelet coefficients

Global positioning system (GPS) common-view observation data were processed by using the multi-scale Kalman algorithm based on a correlative structure of the discrete wavelet coefficients. Suppose that the GPS commonview observation data has the 1/f fractal characteristic, the algorithm of wavelet transform was used to estimate the Hurst parameter H of GPS clock difference data. When 0<H<1, the 1/f fractal characteristic of the GPS clock difference data is a Gaussian zero-mean and non-stationary stochastic process. Thus, the discrete wavelet coefficients can be discussed in the process of estimating multi-scale Kalman coefficients. Furthermore, the discrete clock difference can be estimated. The single-channel and multi-channel common-view observation data were processed respectively. Comparisons were made between the results obtained and the Circular T data. Simulation results show that the algorithm discussed in this paper is both feasible and effective. Translated from Journal of Jilin University (Engineering and Technology), 2006, 36(4): 599–603 [译自: 吉林大学学报 (工学版)]     

FDTD analysis of ground-penetrating radar antennas with shields and absorbers

One of the most critical hardware components of a ground-penetrating radar (GPR) is the antenna system. Important parameters of antennas, such as antenna bandwidth, radiation waveform and cross coupling determine the GPR system performance. The modified TEM horn antenna with distributed resistor load is presented in this paper, and the radiation properties of the antenna with the shields and absorbers are studied through the three-dimensional finite-difference time-domain (FDTD) scheme. Simulations show that the direct signal coupled from the transmitter is decreased by means of the shields and absorbers. Therefore, using the antenna in the GPR system can improve the signal-to-clutter ratio and the dynamic range of the system. __________ Translated from Chinese Journal of Radio Science, 2006, 21(3): 422–427 [译自: 电波科学学报]     

Power allocation scheme for multicell interference coordination in OFDMA systems

To coordinate inter-cell interference, a multicell adaptive power allocation scheme is proposed for downlink orthogonal frequency division multiple access (OFDMA) cellular systems. This scheme uses the difference of the signal to interference plus noise ratio (SINR) between the co-subchannels of adjacent cells to balance SINR for coordinating the transmit power in the co-subchannels. The scheme can improve edge user performance, reduce interference between the co-subchannels of adjacent cells and improve radio resource utility. Simulation results show that the scheme can balance system performance and ensure system throughput. __________ Translated from Journal of Beijing University of Posts and Telecommunications, 2008, 31(1): 71–74 [译自: 北京邮电大学学报]     

Robust adaptive output feedback control of nonlinearly parameterized systems

The ideas of adaptive nonlinear damping and changing supply functions were used to counteract the effects of parameter and nonlinear uncertainties, unmodeled dynamics and unknown bounded disturbances. The high-gain observer was used to estimate the state of the system. A robust adaptive output feedback control scheme was proposed for nonlinearly parameterized systems represented by input-output models. The scheme does not need to estimate the unknown parameters nor add a dynamical signal to dominate the effects of unmodeled dynamics. It is proven that the proposed control scheme guarantees that all the variables in the closed-loop system are bounded and the mean-square tracking error can be made arbitrarily small by choosing some design parameters appropriately. Simulation results have illustrated the effectiveness of the proposed robust adaptive control scheme. Translated from Journal of Sichuan University (Engineering Science Edition), 2006, 38(4): 136–140 [译自: 四川大学学报 (工程科学版)]     

High-speed ground moving target detection research using triangular modulation FMCW

The frequency modulated continuous wave (FMCW) radar has the characteristics of low probability of interception, good hidden property and the ability to counter anti-radiation missiles. This paper proposes a new method for high-speed ground moving target detection (GMTD) using triangular modulation FMCW. According to the characteristic of the opposite range shift induced by the upslope and downslope modulation FMCW, the upslope and downslope are imaged, respectively. After compensation of continuous motion of the platform and time difference between upslope and downslope signals for imaging, the moving target can be detected through displaced phase center antenna (DPCA) technology. When the moving target is detected, the moving target image is extracted, and correlation processing is used to obtain the range shift, which can be used to estimate the target radial velocity, and further to find the real position of the target. The effectiveness of this method is verified by the result of computer simulation. __________ Translated from Journal of Xidian University, 2008, 35(4): 586–591 [译自: 西安电子科技大学学报(自然科学版)]     

Using Petri nets to verify acyclic rule-based system

A series of Petri net-based definitions were formulated for describing four types of structural errors in a rule-based system (RBS), including inconsistency, incompleteness, redundancy and circularity. A marked ω-Petri net model of acyclic RBS was constructed. Then, its reachability tree was generated to record all reachable relations between propositions in RBS. Moreover, a backward reasoning forest of a reachable marking was generated for explicitly representing reachable paths in RBS. Finally, a set of theorems and algorithms were provided to analyze and check structural errors. The usability of the research results presented in this paper was illustrated by an example. __________ Translated from Journal of Tongji University (Natural Science), 2007, 35(2): 232–238 [译自: 同济大学学报(自然科学版)]     

Medical image lossless compression based on combining an integer wavelet transform with DPCM

To improve the classical lossless compression of low efficiency, a method of image lossless compression with high efficiency is presented. Its theory and the algorithm implementation are introduced. The basic approach of medical image lossless compression is then briefly described. After analyzing and implementing differential plus code modulation (DPCM) in lossless compression, a new method of combining an integer wavelet transform with DPCM to compress medical images is discussed. The analysis and simulation results show that this new method is simpler and useful. Moreover, it has high compression ratio in medical image lossless compression. __________ Translated from Journal of Northeastern University (Natural Science), 2007, 28(10): 1454–1457 [译自 : 东北大学学报 (自然科学版)]     

A cross-layer adaptive transmission scheme over correlated fading channels

Conventional adaptive transmission schemes perform poorly in wireless correlated slow-fading channels. A cross-layer adaptive transmission scheme combined with selective repeat automatic repeat request (SR-ARQ) is proposed. We apply a multi-state Markov system model for analyzing the performance of systems and optimizing the selection of modulation levels and packet sizes in correlated fading channels, which is also described by a finite-state Markov chain. A general closed-form expression of the average throughput for our suggested scheme is presented. Numerical results show that our adaptive scheme combined with SR-ARQ can obtain good performance in correlated fading channels. Translated from Journal on Communications, 2006, 45(1): 35–41 [译自: 通信学报]     

Diversity analysis of space-time-frequency coded broadband MIMO-OFDM system with correlation across space time and frequency

For the frequency selective and time variant multiple-input multiple-output (MIMO) channel model taking into account transmitting and receiving antenna correlation, the diversity of space-time-frequency coded broadband orthogonal frequency division multiplexing (MIMO-OFDM) system is analyzed. Based on the average pairwise error probability (PEP), the design criterion of space-time-frequency code (STFC) is expanded. For a given STFC, it is found that the achievable diversity order is related to the transmitter and the receiver correlation matrix as well as the time correlation and frequency correlation matrix. The maximum available diversity of STFC over the correlation channel is Lrank(P)rank(Q)rank(R _T). The space-time code and space-frequency code are special cases in our approach. Simulation results validate the findings. __________ Translated from Journal of Southeast University (Natural Science Edition), 2007, 37(4): 549–553 [译自: 东南大学学报(自然科学版)]     

A novel auto-reference ultra-wideband receiver scheme

A new auto-reference (AR) transmit-receive scheme and a corresponding group decision algorithm on the generalized likelihood ratio testing (GLRT) principle is proposed in this paper to overcome the drawbacks of the power inefficiency and the high noise vulnerability in transmitted-reference (TR) ultra-wideband (UWB) systems. A partly overlapped detection window structure is introduced in which the decided data frames are regarded as the reference signal so that energy and time resources in the reference frame are saved and full-rate data transmission is achieved. Differential coding was utilized to solve the error propagation problem introduced by the overlapped detection windows. The group decision algorithm on the GLRT principle was utilized to estimate the correlation template through all data frames in detection windows and could offer better noise suppression. Simulation results reveal that the AR scheme with its decision algorithm outperforms the conventional and other modified TR schemes in generalized signal-to-noise ratio (SNR). Translated from Journal Xi’an Jiaotong University, 2006, 40(8): 932–935 [译自: 西安交通大学学报]     

Closed-form solutions to fractional-order linear differential equations

The definitions and properties of widely used fractional-order derivatives are summarized in this paper. The characteristic polynomials of the fractional-order systems are pseudo-polynomials whose powers of the complex variable are non-integers. This kind of systems can be approximated by high-order integer-order systems, and can be analyzed and designed by the sophisticated integer-order systems methodology. A new closed-form algorithm for fractional-order linear differential equations is proposed based on the definitions of fractional-order derivatives, and the effectiveness of the algorithm is illustrated through examples. __________ Translated from Journal of Northeastern University (Natural Science), 2007, 28(1): 10–13 [译自: 东北大学学报(自然科学版)]     

Error-space estimate method for generalized synergic target tracking

To improve the tracking accuracy and stability of an optic-electronic target tracking system, the concept of generalized synergic target and an algorithm named error-space estimate method is presented. In this algorithm, the motion of target is described by guide data and guide errors, and then the maneuver of the target is separated into guide data and guide errors to reduce the maneuver level. Then state estimate is implemented in target state-space and error-space respectively, and the prediction data of target position are acquired by synthesizing the filtering data from target state-space according to kinematic model and the prediction data from errorspace according to guide error model. Differing from typical multi-model method, the kinematic and guide error models work concurrently rather than switch between models. Experiment results show that the performance of the algorithm is better than Kalman filter and strong tracking filter at the same maneuver level. __________ Translated from Journal of University of Electronic Science and Technology of China, 2007, 36(2): 217–219 [译自: 电子科技大学学报]     

Design and implement of the signal generator in the magnetic focused conductivity tomography system

To improve stability and performance of the signal source and sweeping detection, as well as to extract abundant and reliable signal, the direct digital synthesis technology was employed to design the generator of the source which formed sweeping frequencies of sine wave output from 1 to 20 MHz. The planar spiral coil was connected as an amplitude modulation circuit. The same coil adopted differential architecture for signal detection and extraction. The MC1595 was utilized to compose a phase detector in which difference of phases varies with the change of frequencies. A low pass filter was designed to filter the carry waves of the sweeping source. Thereby the system gained abundant data and its stability was improved. Further, the spatial resolution of the system was enhanced. All of the above favors the use of software in the magnetic focused conductivity tomography system (MFCT) to reconstruct the image of conductivity within the human body. Translated from Journal of Sichuan University (Engineering Science Edition), 2006, 3(2): 155–158 [译自: 四川大学学报 (工程科学版)]