Table of Content

20 October 2004 Volume 31 Issue 5

  

Original Articles

A realtime and accurate sinusoidal frequency estimation synthetic approach

ZHOU Xi-qing;ZHAO Guo-qing;WANG Wei

J4. 2004, 31(5):  657-660. 

Abstract ( 1670 )   Save

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The method was studied to exactly estimate the frequency of the sinusoidal signal as quickly as possible, which would satisfy the requirements for real-time processing and accuracy. The completed Rife algorithm provided by this paper is a fined frequency estimate that also uses another two spectrum pints beside the maximum spectrum point. In the same condition, it has a lower SNR and is more accurate than the Rife algorithm when the truth frequency is near those spectrum points. But it will have a great deviation when the truth frequency is away from those spectrum points. The synthesized algorithm which is also proved by this paper is another frequency estimate based on the detected maximum spectrum point. First, two spectrum points beside the maximum point are fined at half frequency step, and then the T is used which is the ratio of the new fined spectrum points to determine which algorithm will be empolyed. The modified Rife algorithm is employed as the T>1.5 and the fine completed Rife algorithm is employed as the T≤1.5. 500 simulation for various algorithms show that the synthesized algorithm not only has a good estimation accuracy, but also has a good frequency stability.

Analysis of the dynamic characteristic for the intelligent plate with random parameters

CHEN Jian-jun;WANG Xiao-bing

J4. 2004, 31(5):  661-665. 

Abstract ( 1622 )   Save

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For the intelligent plate containing distributed slices of piezoceramics on its two surfaces, an element model of 12 DOFs with 2 electrical DOFs is adopted and its dynamics differential equations are deduced by means of the Hamilton principle. And then, the Random Factor Method is used to discuss the dynamic characteristic of the intelligent plate with random parameters. Finally, an intelligent cantilever plate is taken as an example, and numerical results of the Random Factor Method are compared with those of the Monte-Carlo Method, by which it is verified that the Random Factor Method is an expedient, comparatively accurate method in dealing with the randomicity of the intelligent plate.

A method to improve the time resolution of the pulse laser range finder using an A/D converter and a look-up table

JIN Wei-sheng;ZENG Xiao-dong;AN Yu-ying

J4. 2004, 31(5):  666-669. 

Abstract ( 1526 )   Save

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A new method for accurate measurement of the time interval is proposed. In the time interval to be measured a given RC circuit is charged, and then the charged voltage across the capacitor is sampled by use of a precision A/D converter. Based on the law of charging, the width of the time interval is obtained by the look-up table method. The theoretical measurement accuracy could be as high as several picoseconds. In addition, this method has a smaller blind region of ranging than that of the analog time interpolation. When a 40MHz clock is used, the blind region of ranging is less than 18m.

The polarization filtering enhancement of the dielectric cylinder target in the rain clutter

WANG Fang;HUANG Ji-ying;GONG Shu-hong

J4. 2004, 31(5):  670-673. 

Abstract ( 1470 )   Save

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The electromagnetic scattering characteristics of rain media and targets are discussed in the polarization field, with the scattering matrix of rain area and targets are obtained. In the millimeter band, the variations are found of the power density of the rain clutter induced by back scattering with frequency and rain rate. The polarization filtering enhancement of the finite length cylinder in rain clutter are numerically modeled. Then, the position on the Poincare sphere corresponding to the maximum SCR can be confirmed, and the optimum polarization state of transmitting and receiving antennas can be given.

System identification study of equivalent complex refraction constant of rain medium

GONG Shu-hong;HUANG Ji-ying;WANG Fang

J4. 2004, 31(5):  674-677. 

Abstract ( 1531 )   Save

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The paper regards rain media as a discrete random system. By estimating the linearity of the system combining the system identification measure with the radio wave propagation theory, th system model is found. Then, the formula for calculating the equivalent complex refraction constant of rain media is deduced. Attenuation induced by rain is prediceted with the equivalent complex refraction constant. The attenuation predicted is nearly consistent with that calculated by the formula recomended in ITU-R and measured results, which testifies that the method used in that paper is effective. It is also helpful for other discrete media.

Analysis of PBG structures in microstrip by modified locally conformal FDTD

SONG Jian;ZHANG Yu;LIANG Chang-hong

J4. 2004, 31(5):  678-681. 

Abstract ( 1515 )   Save

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We present the analysis of some Photonic Band Gap(PBG) structures in microstrip transmission lines by using the Modified Locally conformal Finite Difference Time Domain(MLC-FDTD) Method. Numerical results show that better numerical accuracy can be achieved using this method. The analysis is made to study the influence of the period pattern and the radius of holes etched in the ground plane on the S parameters. Numerical results show that the period pattern determines the central frequency and that the redius of holes influences the width and the depth of the forbidden band.

A novel method of noise reduction based on the signal-adapted orthogonal filter bank

ZHANG Ai-hua1;SHUI Peng-lang2

J4. 2004, 31(5):  682-687. 

Abstract ( 1751 )   Save

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A novel method using signal-adapted filter banks to carry out the noise reduction is investigated. Since signal-adapted filter banks match the statistics of the underlying signal, more efficient signal decomposition can be obtained. The filter banks are designed based on teh low pass subband energy maximum according to the statistics of the signal. Combining signal-adapted filter banks and the traditional thresholding technique, an efficient noise reduction method is presented. Experimental results show that the novel method achieves larger improvement of SNR than the standard filter banks methods at the same filter length.

An algorithm for carrier recovery based on the false frequency offset

ZENG Zhi-bin1;CHU Zhen-yong1;2;YI Ke-chu1

J4. 2004, 31(5):  688-692. 

Abstract ( 1454 )   Save

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The influences of frequency ofset and phase offset on communications are discussed, and then a novel algorithm for recovering the carrier based on the false frequency offset is presented. The proposed algorithm estimates several possible frequency offset values in a wide frequency offset range, and then obtains the true frequency offset value by the false frequency offset elimination method. The novel carrier recovery algorithm also estimates and corrects phase offset by a fast phase offset estimate method. simulation results show the algorithm is less expensive computationally in recovering the carrier.

Wavelet-based on-line state estimate of a nonlinear system

BAO Hong;DUAN Bao-yan;CHEN Guang-da

J4. 2004, 31(5):  693-695. 

Abstract ( 1776 )   Save

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A class of single-input-single-output(SISO) uncertain nonlinear system is concerned. An on-line state estimate algorithm is presented based on a wavelet multiscale analysis. The basic idea is, for the nonlinear system, to perform linear deployment first, then unknown parameters are identified with the application of suitable wavelet functional tests, and finally the best optimizing state estimate of a Kalman is adequately compensated by results obtained. Simulation results are given to demonstrate the effectiveness of the newly proposed method.

Influence factors analysis of the Q-switching result in the multi-direction side-pumped DPL

YANG Ai-fen1;2;GUO Zhen1;WANG Shi-yu1;CAI De-fang1;WEN Jian-guo1

J4. 2004, 31(5):  696-700. 

Abstract ( 1685 )   Save

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A series of experiments on the Q-switching result in different resonators and different locations in the mlti-direction side-pumped DPL has been done. It can be seen from experimental results that the Q-switch location achieving the smallest pulse width, the biggest peak power and the largest Q-switching efficiency is exactly near the oscillating light waist. By discussing this phenomenon, we find the affecting pattern of the oscillating light on output pulse, and learn the influence of pump light on the Q-switching result further. The conclusion of this paper can be used in the optimal design of the acoustics-optical Q-switched multi-direction side-pumped DPL.

Current switch drivers based on high-speed current-steering digital-to-analog convertor dynamic performance

ZHU Zhang-ming;YANG Yin-tang;LIU Li;LIU Lian-xi

J4. 2004, 31(5):  701-704. 

Abstract ( 1479 )   Save

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Based on the analysis of teh influence of the current switc driver on dynamic performance of the high-speed current-steering D/A converter, the design principle of the current switch driver is proposed. The crossing point theory, synchronous flip-latch and limited swing driver are included in the principle, and a novel current switch driver circuit is proposed in TSMC 0.35μm CMOS technology. The driver circuit is simulated and analyzed by Hspice. The 4-bit D/A converter introduced novel driver has low glitch energy, and the 8-bit segmented D/A converter introduced novel driver has high SFDR. The simulated results show that the principle and the driver are very useful to the high speed D/A converter design with good dynamic performance.

A norm method for noncoherent despreading/demodulation signal

CHU Zhen-yong1;2;YI Ke-chu1;TIAN Hong-xin1

J4. 2004, 31(5):  705-708. 

Abstract ( 1498 )   Save

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The energy calculation of the noncoherent despreading/demodulation signal was extended into vector norm calculation based on the equivalence property theory of vector norm in the orthogonal codes spread spectrum system. Because the different kinds of norms need the different computation and complexity, we should choose the most suitable vector norm to process the despreading signals for simplifying the hardware circuit. Finally, we discussed the FPGA designs of three kinds of noncoherent despreading/demodulation signal processing units, which were realized by the 2-norm method, 1-norm method and ∞-norm method respectivel, and then offered their BER curves.

Efficient implementation of the sum-product algorithm for quantized decoding of LDPC codes

TONG Sheng;WANG Peng;WANG Dan;WANG Xin-mei

J4. 2004, 31(5):  709-713. 

Abstract ( 1818 )   Save

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An efficient implementation of the sum-product algorithm(SPA) in the log-likelihood ratio(LLR) domain is presented in [1]. In this paper, we modify a formula in [1] such that SPA can be implemented by using two small look-up tables. With this modification, all the calculations involved in this implementation involve only additions, subtractions, comparisons and table looking-ups, which leads to low computation complexity and facility in hardware implementation. Based on this modified implementation, various quantization schemes of SPA for decoding low-density parity-check(LDPC) codes are investigated. And the issues related to quantization, such as clipping levels and variables' quantization, are also investigated. Simulation results show that the performance of the uniform quantization scheme is very close to that of the non-quantization over the AWGN channel. Moreover, it can obtain the same performance as that of non-quantization at high SNRs.

Parallel architecture in VLSI implementation of the MQ-coder for JPEG2000

CAO Bin;LI Yun-song;LIU Kai;DENG Jia-xian

J4. 2004, 31(5):  714-718. 

Abstract ( 2030 )   Save

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Hardware implementation of the MQ-coder for JPEG2000 standard is investigated. An efficient method for VLSI implementation described in VDHL is presented on the basis of making full use of parallel architecture. Pipe-line architecture used in this design makes several actions performed in parallel in general structure. Parallel output architecture solves the problem of generating two bytes of compressed data in one clock, and at the same time greatly improves the efficiency of producing output data. The stimulation results testify that this implementation can not only ensure the correctness, but meet the needs of the JPEG2000 coding system both in efficiency and resource occupancy.

Copyright protection of the vector map using the digital watermark

LI Yuan-yuan1;XU Lu-ping1;2

J4. 2004, 31(5):  719-723. 

Abstract ( 1701 )   Save

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An algorithm for watermarking of the vector map is presented. We lay a rectangular grid over the map; according to the classification of density of vertices in each block we modulate the intensity of watermark adaptively, in the tolerance of the coordinates, and a two-value watermark image is embedded repeatedly by displacing the coordinates of vertices. When extracting the watermarks double-threshold combinative detection is used, the proposed algorithm can enhance the intensity of watermarks and ensure the precision and usability of the map. Experimental results show that this algorithm is robust to some processing.

SAF: semi-fragile authentication watermarking with feedback

ZHANG Yong-ping;GUO Bao-long

J4. 2004, 31(5):  724-727. 

Abstract ( 1381 )   Save

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The well-known adage that "seeing is believing" is no longer true due to the pervasive and powerful multimedia manipulation tools. To prevent image manipulations and fraudulent use of modified images, multimedia authentication techniques are being developed. But nfortunately there is a big problem in authentication watermarking algorithms which are in the transform(e.g., DCT) domain. Converting the modified transform coefficients back to the integer pixel domain and then converting them again to the transform domain may not have been manipulated otherwise. Combining the embedding process with the performance analysis, a new semi-fragile authentication watermarking with feedback, called SAF, is presented. The embedding process in some image blocks is performed several times according to the results of the performance analysis of the watermarking detecting process. By the reconstruction of the DCT coefficient, SAF can accept JPEG lossy compression on the watermarked image to a pre-determined quality factor, and reject malicious attacks. The experimental results show its effectiveness in protecting the content-integrity of images.

A modeling algorithm for generating terrain in virtual environment

LI Guang-xin;WU Zi-li;DING Zhen-guo;ZHOU Li-hua

J4. 2004, 31(5):  728-731. 

Abstract ( 1609 )   Save

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The paper presents a modeling algorithm for generating terrain in virtual environment. Perlin noise is introduced as the generator of terrain height, which results in a 3D terrain height field of a given 2D terrain area. The terrain is continuous to some degree in virtue of the smoothness characteristic of the noise. By controlling the frequency and amplitude of Perlin noise and superposing more noise value, we can get diversified terrain with the complex work of manual geometry modeling avoided. 3D texture technology is used to map different textures on part of terrain with different heights to simulate diverse environment. A script language is designed to describe the terrain. The script can act as driving data to construct terrain quickly and conveniently in virtual environment application. It turns out that the terrain generated is realistic and that our algorithm satisfies the requirements of real time virtual environment system based on the general PC platform.

Measurement determination of copling parameters between adjacent elements in an active integrated antenna array

AI Bao-qiang;CHU Qing-xin;LEI Zhen-ya

J4. 2004, 31(5):  732-735. 

Abstract ( 1667 )   Save

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In order to accurately design an active antenna array, coupling parameters between adjacent elements must be determined. The coupling parameters, however, cannot be described in a simple expression. In this paper, the coupling parameter is determined through measurement and curve fitting according to the dynamic equations for active antenna arrays. The resulting coupling parameters are applied to design a two-element active antenna array to check validity of the method. It is shown that theoretical results are in good agreement with measurement results.

Suppression of the fast follower jammer using adaptive beamforming

DUAN Zhi-qiang;ZHANG Lin-rang;SU Tao;MA Da-yuan

J4. 2004, 31(5):  736-739. 

Abstract ( 1716 )   Save

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The interference-resist ability can be improved by a combination of the adaptive antenna with the frequency-hopping(FH) technique. In order to effectively decrease the influence of the fast follower jammer on a frequency-hopping(FH) system, frequency compensation must be considered. A new frequency compensation method is presented, which uses the focusing matrix of the coherent signal-subspace method(CSM) to update the data matrix before the fast follower jammer's arrival. The convergence of the adaptive beamformer is improved by using the method. Computer simulation results demonstrate the effectiveness of the proposed method.

Adaptive TWTA pre-distorter based on vector quantization

GU Chun-yan;YI Ke-chu

J4. 2004, 31(5):  740-743. 

Abstract ( 1627 )   Save

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The TWT amplifier exhibits nonlinear distortions in both amplitude(AM/AM) and phase(AM/PM), which can lead to signal distortion. So linearization technique is needed for amplifiers. Among a lot of techniques proposed, the pre-distorter based on direct maping is simple and effective. Based on the vector quantization technique, this paper impves the "direct mapping pre-distorter," presents a new adaptive predistorion technique for compensating for nonlinear distortions. Compared with the "direct mapping pre-distorter," this technique not only can decrease memory while maintaining compensation precision, but also can be aplied to input signals with different quantization bits, thus resulting in a great flexibility.

Multiuser detector based on the support vector machine in the TD-SCDMA system

WANG Yong-gang1;2;JIAO Li-cheng1

J4. 2004, 31(5):  744-748. 

Abstract ( 1759 )   Save

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A nonlinear multiuser detector based on the support vector machine(SVM) is presented. The presented detector can approach the optimum multiuser detector by using the Midamble of TD-SCDMA. Structural risk minimization(SRM) introduced in SVM leads to the greater generalization and fewer training samples than the other learning models. The nonlinear support vector machine multiuser detector can approach the optimum multiuser detector in a better way than the other linear detectors. The resuls of simulation show the feasibility and validity of this detector in the multipath channel.

Analysis of the micro-cantilever rough surface adhesion model

TIAN Wen-chao;JIA Jian-yuan

J4. 2004, 31(5):  749-752. 

Abstract ( 1598 )   Save

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"Stick" affects the performance and reliability of the MEMS device greatly. The "cutting-ball" adhesion model of the micro-cantilever rough surface is set up on the basis of the three hypotheses. By the Hamaker micro continuum medium method and gap revision principle, the adhesion mathematical model is found. The adhesion simulation results are obtained, and followed by the discussion of the rough degree influence on adhesion.

Bit plane-parallel VLSI architecture for a modified SPIHT algorithm using depth-first search bit stream processing

LIU Kai;WU Cheng-ke;LI Yun-song;ZHUANG Huai-yu

J4. 2004, 31(5):  753-756. 

Abstract ( 2249 )   Save

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We present a bit plane-parallel architecture for a modified SPIHT algorithm using depth-first search bit stream processing which is suitable for VLSI implementation. In the architecture, the coding information of each bit plane can be obtained simultaneously. that is, the ancestor-descendant relationship between coefficients of the tree stucture can be calculated by logical operators. Then, the corresponding VLSI architecture for implementing the formulated requirements is presented. Compared with other architectures, this has advantages of high parallelism, no intermediate buffer and the ability to scan with error resilience as a single tree. The experimental results show that the proposed architecture reduces the processing time greatly compared with others. The quality of images can satisfy most application fields.

Convertible designated confirmer partially blind signatures

HUANG Zhen-jie1;2;HAO Yan-hua1;WANG Yu-min1

J4. 2004, 31(5):  757-760. 

Abstract ( 2130 )   Save

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The concept of partially blind signature is extended to the convertible designated confirmer partially blind signature, which has an additional property that only the designated confirmer and the user can verify and prove the validity of given signatures and convert given signatures into universally verifiable partially blind signatures. A formal definition is given and a practical scheme is proposed. The proposed scheme is efficient and secure, in which its unforgeability is the same as that of the Schnorr's signature scheme and its untransferability relies on the hardness of the Decision-Diffie-Hellman problem. Furthermore, the proposed scheme can be used as a normal partially blind signature scheme by letting the designated confirmer's secret key be a common constant.

Improvement on the performance of the auxiliary channel STAP in the non-homogeneous environment

WANG Wan-lin;LIAO Gui-sheng;ZHANG Guang-bin

J4. 2004, 31(5):  761-764. 

Abstract ( 1815 )   Save

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The auxiliary channel processing(ACP) is one of the reduced rank methods for space time processing(STAP) clutter mitigation. However, the ACP technique has an imperfection of signal self-nulling by the correlation between the clutter in the auxiliary channel and the signal in the main channel due to the limited samples in the non-homogeneous environments. Thus, a new method for clutter mitigation based on ACP for phased array airborne early warning(AEW) radar was proposed, which aims at avoiding the bad effect of the target signal in the adaptive weight training, and its detailed realization structure was also given. The new method is very robust whether the target exists training, and its detailed realization structure was also given. The new method is very robust whether the target exists or not, therefore greatly improving the target test performance. The final computation experiments also prove the effectiveness of the proposed method.

A novel scheduling strategy for broadband multimedia satellite networks

WANG Kai-dong;YI Ke-chu;TIAN Bin

J4. 2004, 31(5):  765-769. 

Abstract ( 1648 )   Save

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This paper proposes a novel scheduling strategy for broadband multimedia satellite networks. It is composed of the ground local scheduler and on-board global scheduler. Because most of the complexity that is added to the satellite network is confined to the ground segment, the scheduling strategy minimally affects the design of the on-board processing(OBP). Simulation shows that it is a highly efficient scheduling strategy which not only reduces the end-to-end delays endured by the best effort connections but also minimizes the degradation of VBR and ABR connections with increased frame utilization performance.

Anisotropic PML absorbing boundary for FDTD in generalized orthogonal coordinates

CHEN Lin;LIU Qi-zhong;JI Yi-cai

J4. 2004, 31(5):  770-773. 

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A simple and systematic derivation of anisotropic perfectly matched layer(APML) for the finite-difference time-domain(FDTD) method in generalized orghogonal coordinates(GOC) is presented. The derivation is based on the complex coordinate stretching approach. Through mapping matrix presentation of Maxwell's equations in a complex coordinate system into the real one, the constitutive tensor of this APML is simply obtained from teh Lame coefficients of the coordinate. Numerical results illustrate the effectivenss of absorbing in this APML.

An adaptive beamforming algorithm in the presence of coherent interference

CAO Yun-he;ZHANG Shou-hong;ZHAO Yong-bo

J4. 2004, 31(5):  774-776. 

Abstract ( 1525 )   Save

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Based on the ESB method, this paper presents a novel beamforming algorithm for the uniform linear array which constructs a special matrix instead of the convariance matrix. The algorithm can overcome the problem that the ESB can not work n the environment of coherent signals. Moreover, the algorithm can converge rapidly and keep a good performance in a low SNR and a little snaphshots.

A timestamp-based registration protocol in mobile IP

WANG Li-ming;YANG Bo

J4. 2004, 31(5):  777-780. 

Abstract ( 1555 )   Save

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Mobile IP is widely used in today's life, and then how is its security ensured? This paper deals mainly with the security aspect of the registration procedure in Mobile IP. We present a timestamp-based registration protocol. The public-key mechanism and timestamp are both used for entity authentication. The private-key mechanism is also used by the mobile node to achieve mutual authentication between itself and home agent, in the case where mobile agent's computational power is limited.

Analysis of the availability of component-based software systems

WANG Chao;ZHU Jian-ming;MA Jian-feng

J4. 2004, 31(5):  781-784. 

Abstract ( 1297 )   Save

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System failures of the component-based software systems are mainly caused by component failures and component interface failures. The two kinds of failures and their repairs were seldom considered simultaneously in the previous studies of software system availability. System availability is analyzed. The system states are described by the states of the components, the failures and their repairs by component state transitions, and the system state transitions by continuous time Markov chain(CTMC). Thus the two kinds of failures and their repairs are considered at the same time. Finally a case study is discussed to compare the effects of the two kinds of failure rates o the software system availability.

An approach to the formal analysis of the TMN protocol

LIU Xiu-ying1;2;ZHANG Yu-qing2;YANG Bo1;XING Ge2

J4. 2004, 31(5):  785-790. 

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This paper analyzes the TMN protocol comprehensively using a formal analysis method called the running-mode analysis and uncovers a number of attacks on the TMN protocol. According to the detailed forms of these attacks and the different intentions of the intruder, we classify these attacks. Finally, linking with known attacks, we deduce that the running-mode analysis has analyzed the TMN protocol effectively.

Analysis of the localization errors in the netted passive sensor system

LIU Zong-xiang1;XIE Wei-xin2;YANG Xuan2

J4. 2004, 31(5):  791-795. 

Abstract ( 1604 )   Save

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The analysis of the localization errors in a netted passive sensor system plays an important role in the selection of the passive sensors and the allocation of the posts. In order to solve the problem of the error analysis, the analytical method for the localization errors is proposed. Finally, the distributing features and regularity of errors in two-sensor and three-sensor systems are analyzed through simulation calculation.

A solvable necessary and sufficient condition for the second order linear differential equation with variable coefficients

YAN En-rang

J4. 2004, 31(5):  796-798. 

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The solvability of the second order linear differential equation with variable coefficients y″+P(x)y′+Q(x)y=f(x) is studied. A solvable necessary and sufficient condition: P(x)=bG(x)-G′(x)/G(x)-2F(x)，Q(x)=F²(x)-F′(x)-F(x)(bG(x)-G′(x)/G(x))+cG²(x). (F(x), G(x)∈C¹, G(x)≠0, b and c is constant) is obtained. Moreover, some solving processes and formula for teh general solution are given.

Research on ISAPI--based communication engineer PM system design

YANG Xiang-chi;LI Peng-fei

J4. 2004, 31(5):  799-802. 

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This paper gives framework model of PM system, and introduces ISAPI technology, and the developing process of communication engine PM system based on ISAPI, and gives PM system function, system structure, software design in detail.

The effect of MAI on the WCDMA property

LIU Yuan;WANG Xiang-hua;LUO Yun-fan

J4. 2004, 31(5):  803-806. 

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Based on the Okumura-Hata propagation model, we analyze theoretically and effect of MAI on the WCDMA property, and educe the relation between MAI and coverage and capacity. The result of simulation indicates that, when MAI rises by 1dB, the WCDMA coverage area will reduce by 12%, and that the MAI's increase also reduces capacity. In a word, this effect will be different if the NodeB antenna's height, NodeB transmit signal power or cell coverage radius is different.

High-power millimeter wave mode converter in an overmoded circular waveguide

ZHU Lian-xuan1;NIU Xin-jian2

J4. 2004, 31(5):  807-810. 

Abstract ( 1350 )   Save

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Based on the mode coupling theory, the design of TM₀₁-TE₁₁，TE₀₁-TM₁₁，TE_0n-TE₀₁，TE₀₁-TE₁₁ overmoded circular waveguide mode converter geometric configurations with different phase rematches and structures is given to obtain more acceptable geometry parameters. This result contributes to teh design of a corresponding circular waveguide mode converter with compactness high efficiently and a wideband.

A fair multi-party exchange protocol with the off-line trusted third party

LI Yan-ping;ZHANG Jian-zhong

J4. 2004, 31(5):  811-814. 

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The difference between teh fair exchange protocols and the non-repudiation protocols is proposed. Based on the publicly verifiable secret sharing scheme and group encryption scheme, a new multi-party fair exchange protocol with an off-line semi-trusted third party(off-STTP) is presented. The off-STTP who need not be completely trusted intervenes into the exchange in case of trouble. That the off-STTP can only decipher a sub-secret key makes sure the confidentiality of exchange data and the true fairness of the barter. The participants can barter with others at their will and the exchange topology is unknown to others including the off-STTP.

Study of the shadow zone of the radar in the atmospheric duct

JIAO Lin;ZHANG Yong-gang

J4. 2004, 31(5):  815-820. 

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From the shadow of the radar in the standard atmosphere, the paper studies the characteristics and distributing features of the atmospheric duct. Using the simulating test, we analyze the shadow of the radar in the atmospheric duct with different electromagnetic parameters of the radar, atmospheric duct parameters and terrain factor parameters. The study will offer the credible gist for using the radar, and establish the academic groundwork for the applied research of the shadown of the radar.