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[Keyword] ARF(9hit)

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  • Optimization of a Sparse Array Antenna for 3D Imaging in Near Range

    Andrey LYULYAKIN  Iakov CHERNYAK  Motoyuki SATO  

     
    BRIEF PAPER

      Vol:
    E102-C No:1
      Page(s):
    46-50

    In order to improve an imaging performance of a sparse array radar system we propose an optimization method to find a new antenna array layout. The method searches for a minimum of the cost function based on a 3D point spread function of the array. We found a solution for the simulated problem in a form of the new layout for the antenna array with more sparse middle-point distribution comparing with initial one.

  • Radar Modulation Identification Using Inequality Measurement in Frequency Domain

    Kyung-Jin YOU  Ha-Eun JEON  Hyun-Chool SHIN  

     
    PAPER-Digital Signal Processing

      Vol:
    E100-A No:4
      Page(s):
    975-981

    In this paper, we proposed a method for radar modulation identification based on the measurement of inequality in the frequency domain. Gini's coefficient was used to exploit the inequality in the powers of spectral components. The maximum likelihood classifier was used to classify the detected radar signal into four types of modulations: unmodulated signal (UM), linear frequency modulation (LFM), non-linear frequency modulation (NLFM), and frequency shift keying (FSK). The simulation results demonstrated that the proposed method achieves an overall identification accuracy of 98.61% at a signal-to-noise ratio (SNR) of -6dB without a priori information such as carrier frequency, pulse arrival times or pulse width.

  • Optimal Decision-Making of Countermeasures by Estimating Their Expected Utilities

    So Ryoung PARK  Sanguk NOH  

     
    PAPER-Distributed Cooperation and Agents

      Vol:
    E93-D No:3
      Page(s):
    560-568

    This paper investigates the autonomous decision-making process of the selection of alternative countermeasures against threats in electronic warfare settings. We introduce a threat model, which represents a specific threat pattern, and a methodology that decides the best countermeasure against real-time threats using the decision theory. To determine the optimal countermeasure, we model the probabilities of the effects of countermeasures, if executed, and combine the probabilities with their utilities. This methodology based upon the inductive threat model calculates the expected utilities of countermeasures which are applicable given a situation, and provide an intelligent command and control agent with the best countermeasure to threats. We present empirical results that demonstrate the agent's capabilities of choosing countermeasures to threats in simulated electronic warfare settings.

  • Rate Adaptation Based on Collision Probability for IEEE 802.11 WLANs

    Taejoon KIM  Jong-Tae LIM  

     
    LETTER-Terrestrial Radio Communications

      Vol:
    E91-B No:4
      Page(s):
    1227-1230

    Nowadays IEEE 802.11 wireless local area networks (WLANs) support multiple transmission rates. To achieve the best performance, transmitting stations adopt the various forms of automatic rate fallback (ARF). However, ARF suffers from severe performance degradation as the number of transmitting stations increases. In this paper, we propose a new rate adaptation scheme which adjusts the ARF's up/down threshold according to the channel contention level. Simulation result shows that the proposed scheme achieves fairly good performance compared with the existing schemes.

  • Performance Analysis of IEEE 802.11 DCF in a Multi-Rate WLAN

    Weikuo CHU  Yu-Chee TSENG  

     
    PAPER-Network

      Vol:
    E90-B No:10
      Page(s):
    2836-2844

    The IEEE 802.11 family of specifications is by far the most prominent and successful technique for accessing WLANs. Because the channel used by wireless devices is a time-varying broadcast medium, these devices need to have multi-rate and rate-adaptive capability to adapt to the changing channel so that better performance can be achieved. In this paper, we propose an analytical model, which we call Rate-Adaptive Markov Chains, to study the saturation throughput and delay performance of an 802.11 WLAN in which the mobile hosts have multi-rate support, will use the ARF protocol to adapt rates for different channel qualities, and follow the DCF protocol to contend for data transmissions in a slowly-varying channel. Simulation results are also provided to verify the correctness of the model.

  • Improvement of ArF Photo Resist Pattern by VUV Cure

    Hisakazu MIYATAKE  Takashi ITO  

     
    PAPER-Lithography-Related Techniques

      Vol:
    E90-C No:5
      Page(s):
    1006-1011

    The dry etching resistance of ArF resist patterns was improved by irradiating vacuum ultraviolet (VUV) light with a wavelength of 172 nm to ArF resist patterns in N2 atmosphere. The density of C=O bonds of the resists is decreased, and the dry etching rate of resist is also decreased after VUV irradiation. The line width shrinkage by the electron beam irradiation of CD-SEM was greatly improved from 9 nm to 2 nm, and LER (Line Edge Roughness) of resist patterns was approximately 2 nm improved from 8.4 nm to 6.5 nm under VUV irradiation. Using VUV cure, the dry etching pattern of a SiN film showed a rectangle-like cross-sectional view, and indicated almost the same LER value as the resist mask pattern. The VUV cure technique is an attractive method of fine resist pattern fabrication by ArF lithography.

  • Recognition of PRI Modulation Types of Radar Signals Using the Autocorrelation

    Young-Jin RYOO  Kyu-Ha SONG  Whan-Woo KIM  

     
    LETTER-Sensing

      Vol:
    E90-B No:5
      Page(s):
    1290-1294

    In electronic warfare support systems, the analysis of PRI (Pulse Repetition Interval) modulation characteristics for a radar pulse signal has attracted much interest because of the problem of the identification ambiguity in dense electronic warfare signal environments. A new method of recognizing the PRI modulation type of a radar pulse signal is proposed for electronic warfare support. The proposed method recognizes the PRI modulation types using classifiers based on the property of the autocorrelation of the PRI sequences for each PRI modulation type. In addition, the proposed method estimates the PRI modulation period for the PRI modulation type with the periodicity. Simulation results are presented to show the performance of the proposed method.

  • Mobile Agents in Network-Centric Warfare

    Marion G. CERUTI  

     
    LETTER

      Vol:
    E84-B No:10
      Page(s):
    2781-2785

    This paper describes agent technology and the various ways in which it can be applied to command, control, communications and intelligence in general, and to network-centric warfare in particular. The paper provides a brief overview of agents, their properties, and their advantages. It covers the concept of the current military trend, network-centric warfare. Problems associated with agents are described, including the conflict between security and autonomy, in a distributed environment. The paper concludes with a discussion of research trends in mobile agents, particularly with regard to applications in the Department of Defense.

  • Development of Transparent Alkylsulfonium Salt as a Photoacid Generator for ArF Excimer Laser Lithography

    Kaichiro NAKANO  Katsumi MAEDA  Shigeyuki IWASA  Etsuo HASEGAWA  

     
    PAPER

      Vol:
    E81-C No:7
      Page(s):
    1045-1050

    A series of transparent photochemical acid-generators (PAGs) has been successfully prepared and investigated to apply ArF excimer-laser lithography. These PAGs were synthesized as new alkylsulfonium salts that have cycloalkyl groups but no aromatic ones. They were almost transparent at 193. 4 nm and have high acid-generation efficiency enough to use for ArF excimer-laser resists. The photochemical reaction of these alkylsulfonium salts occurs mainly due to the S-C bond fission. A resist utilizing the PAGs was capable to resolve a 0. 2µm L/S pattern at a 50-mJ/cm2 dose with an aqueous alkaline developer. These PAGs are promising materials for use in ArF excimer-laser lithography.