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)]     

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]     

New mutual coupling compensation method and its application in DOA estimation

A new mutual coupling compensation method based on a new mutual impedance matrix, as well as its application to dipole arrays, are proposed. This new mutual impedance matrix is deduced by electromotive force (EMF) method, based on the current distribution obtained by the characteristic basis function method. It appears in a concise and explicit formulation that facilitates the numerical calculation. The compensation performance is demonstrated and evaluated through its application in direction of arrival (DOA) estimation. Numerical results show that the proposed method exhibits excellent compensation performance compared with conventional mutual impedance matrix approaches. __________ Translated from Chinese Journal of Radio Science, 2007, 22(4): 541–545 [译自: 电波科学学报]     

Analysis of the diffracted current basis functions used in the hybrid MoM-PO method

The combined moment method (MoM)-physical optics (PO) approach proposed by Bilow fails in some cases. Based on the theory of diffraction and the fundamental theory of electromagnetism, Bilow’s diffracted current basis function was modified both within and outside the transition regions. The improved MoM-PO technique is validated by comparison with exact solutions for a right-angled perfectly conducting wedge at normal incidence. Translated from Chinese Journal of Radio Science, 2006, 21(4):514–517 [译自: 电波科学学报]     

Positioning models and systems based on digital television broadcasting signals

The requirement and feasibility of the positioning system using digital television (DTV) broadcasting signals are analyzed. The principle of DTV positioning on the basis of frame synchronization is brought forward and the ranging characteristic is studied that the observables are asynchronously measured during the same epoch interval. The models of the pseudo-range observation and Doppler carrier phase integral are researched. The system observation and state equations are presented on the basis of the above models. The simulation results showed that DTV positioning technology could remarkably improve the precision of system state estimates using smoothing methods for positioning systems or integrated navigation systems. The DTV positioning that has a sub-meter level ranging error and meter level positioning accuracy can parallel with and even taken as a beneficial substitute for the tradition positioning technology. __________ Translated from Journal of Southeast University (Natural Science Edition), 2006, 36(5): 690–694 [译 自: 东南大学学报(自然科学版)]     

Pattern synthesis of antennas based on a modified particle swarm optimization algorithm

In order to overcome the drawbacks of standard particle swarm optimization (PSO) algorithm, such as prematurity and easily trapping in local optimum, a modified PSO algorithm is proposed, in which special techniques, as global best perturbation and inertia weight jump threshold are adopted. The convergence speed and accuracy of the algorithm are improved. The test by some benchmark problems shows that the proposed algorithm achieves relatively higher performance. Thereafter, the applications of the modified PSO in the radiation pattern synthesis of antenna arrays are presented. __________ Translated from Chinese Journal of Radio Science, 2006, 21(6): 873–878 [译自: 电波科学学报]     

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)]     

Recurrent neural networks-based multivariable system PID predictive control

A nonlinear proportion integration differentiation (PID) controller is proposed on the basis of recurrent neural networks, due to the difficulty of tuning the parameters of conventional PID controller. In the control process of nonlinear multivariable system, a decoupling controller was constructed, which took advantage of multi-nonlinear PID controllers in parallel. With the idea of predictive control, two multivariable predictive control strategies were established. One strategy involved the use of the general minimum variance control function on the basis of recursive multi-step predictive method. The other involved the adoption of multistep predictive cost energy to train the weights of the decoupling controller. Simulation studies have shown the efficiency of these strategies. Translated from Acta Scientiarum Naturalium Universitatis Nankaiensis, 2006, 39(1): 49–53 [译自: 南开大学学报 (自然科学版)]     

Analysis of electromagnetic field emitted from home plug power line used for indoor high-speed broadband communication

High-speed broadband power line communication (BPL) is a novel and practicable technique for Net-atHome or home area local area networking (LAN). Because of the characteristics of BPL, the electromagnetic wave emitted from the BPL transmission media will influence the indoor electromagnetic environment, which would also affect the performance of other wireless communications. Based on the analysis of the communication channel characteristic, network impedance and attenuation characteristic of the BPL, this paper proposes a novel model for calculating the BPL radiation and the computer simulation model, which are proved by the coherence of the simulation and the test data. The interferences from the high-speed BPL to indoor wireless communications are analyzed to stipulate the standards of high-speed BPL in the future. __________ Translated from Chinese Journal of Radio Science, 2008, 23(3): 539–544 [译自: 电波科学学报]     

Image adaptive RST invariant watermark using pseudo-Zernike moments

Rotation, scaling and translation (RST) attacks can desynchronize watermark detection, which causes failure in many watermarking systems. In this paper, an image adaptive RST invariant watermark (AWPZM) is proposed by using the rotation invariant property of pseudo-Zernike moments (PZM) and oddeven quantization. PZM of the original image is computed first, and then those suitable for watermark generation are selected. Then, magnitudes of them are odd-even quantized to generate the watermark. In detection, a normalized hamming function is employed to determine the similarity of the watermark. Experimental results show its robustness to rotation and scaling. For traditional attacks, such as JPEG compression, added noise and filtering, the similarities are all above 0.95. __________ Translated from Journal of Xidian University, 2007, 34(1): 38–42 [译自: 西安电子科技大学学报]     

A novel distributed algorithm for media access control address assignment in wireless sensor networks

This paper presents a novel distributed media access control (MAC) address assignment algorithm, namely virtual grid spatial reusing (VGSR), for wireless sensor networks, which reduces the size of the MAC address efficiently on the basis of both the spatial reuse of MAC address and the mapping of geographical position. By adjusting the communication range of sensor nodes, VGSR algorithm can minimize the size of MAC address and meanwhile guarantee the connectivity of the sensor network. Theoretical analysis and experimental results show that VGSR algorithm is not only of low energy cost, but also scales well with the network size, with its performance superior to that of other existing algorithms. __________ Translated from Journal of Xidian University, 2006, 33(5): 716–720 [译自: 西安电子科技大学学报 (自然科学版)]     

Routing and wavelength assignment in hierarchical WDM networks

A new routing and wavelength assignment method applied in hierarchical wavelength division multiplexing (WDM) networks is proposed. The algorithm is called offline band priority algorithm (offline BPA). The offline BPA targets to maximize the number of waveband paths under the condition of minimum number of wavelengths, and solve the routing and wavelength assignment (RWA) problem with waveband grooming to reduce cost. Based on the circle construction algorithm, waveband priority function is introduced to calculate the RWA problem. Simulation results demonstrate that the proposed algorithm achieves significant cost reduction in WDM network construction. __________ Translated from Journal of Shanghai Jiaotong University, 2007, 41 (5): 747–750 [译自: 上海交通大学学报]     

Droplets actuating chip based on electrowetting-on-dielectric

A droplet-based actuating chip by using the method of electrowetting-on-dielectric (EWOD) was developed to manipulate the microfluidics. Here, the actuation mechanism of the sandwiched-configuration EWOD chips was carefully studied, and the movement of droplets was numerically analyzed by using the computational fluidic software, CFD-ACE+. The fabrication of the chip, including a heavily phosphorus-doped poly-silicon micro-electrode array and a thermally grown SiO₂ dielectric layer, was exploited to improve the chip stability and decrease the actuation voltage. In experiments, the transportation of a deionized droplet of about 0.5 μL is successfully achieved in air by applying the low voltage of 45 V. Translated from Journal of Tsinghua University (Science and Technology), 2006, 46(7): 1 341–1 344 [译自: 清华大学学报 (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]     

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)]     

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)]     

UWB planar antenna technology

Recent developments of the ultra-wideband (UWB) planar antennas are reviewed, where the progress in UWB plate monopole antennas, UWB printed monopole antennas and the UWB printed slot antennas is introduced and compared. In addition, the UWB printed antennas with the band-notched functions are also presented. __________ Translated from Chinese Journal of Radio Science, 2007, 22(2): 308–315 [译自: 电波科学学报]     

Loaded-frequency selective surface

A new frequency-selective surface (FSS) with loadings is introduced in this paper and analyzed by way of period moment methods (PMMs). The simulated results show that FSS may operate in different bands and especially generate a large reduction in the resonant frequency for a fixed unit cell size through different loadings. This provides a new orientation in the development for FSS. Practical circuits are fabricated, and the measured results agree well with the simulated results. __________ Translated from Chinese Journal of Radio Science, 2006, 21(3): 441–444 [译自: 电波科学学报]     

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)]     

Robust adaptive beamforming algorithm based on Bayesian approach

The performance of adaptive array beamforming algorithms substantially degrades in practice because of a slight mismatch between actual and presumed array responses to the desired signal. A novel robust adaptive beamforming algorithm based on Bayesian approach is therefore proposed. The algorithm responds to the current environment by estimating the direction of arrival (DOA) of the actual signal from observations. Computational complexity of the proposed algorithm can thus be reduced compared with other algorithms since the recursive method is used to obtain inverse matrix. In addition, it has strong robustness to the uncertainty of actual signal DOA and makes the mean output array signal-to-interference-plus-noise ratio (SINR) consistently approach the optimum. Simulation results show that the proposed algorithm is better in performance than conventional adaptive beamforming algorithms. __________ Translated from Journal of Northeastern University (Natural Science), 2007, 28(6): 793–796 [译自: 东北大学学报 (自然科学版)]