김영수 Young Su Kim , 강흥용 Heung Yong Kang , 김창주 Chang Joo Kim

DOI: JANT Vol.6(No.3) 181-187, 2002

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In this paper, we propose a resolution enhancement method for estimating direction-of-arrival(DOA) of narrowband incoherent signals incident on a general array. The resolution of DOA algorithm is dependent on the aperture size of antenna array. But it is very impractical to increase the physical size of antenna array in real environment. We propose the method that improves resolution performance by virtually expanding the sensor spacing of original antenna array and then averaging the spatial spectrum of each virtual array which has a different aperture size. Superior resolution capabilities achieved with this method are shown by simulation results in comparison with the standard MUSIC for incoherent signals incident on a unuform circular array.

임윤두 Yun Doo Lim , 고봉진 Bong Jin Ko

DOI: JANT Vol.6(No.3) 188-194, 2002

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DBS is utilized as very useful media in information-oriented society because it covers wide service area and provide high quality services. But DBS needs skill that can receive DBS signal at move. In this paper, it is considered a development of a device to receive DBS and design of a low noise downcoverter that use tracking antenna to receive DBS at mobiles unit and ships which navigate in Korea peninsula coast. The structure of dual phase LNB is composed of LNA, BPF, oscillator, mixer, and IF amplifier. And for the position tracking, two input-output phase performed inphase. Measured results showed good performance that with respect to input signal 11.7 GHz ~ 12.2 GHz. noise figure is 0.87 dBmax and conversion gain 62 dB, temperature characterization ±400 kHz in respect to -30 to 60℃, and phase noise -101 dBc/Hz in respect to offset 100 kHz.

고윤선 Yun Sun Ko , 정재필 Jae Pil Chung , 오창헌 Chang Heon Oh , 신동욱 Dong Uk Shin

DOI: JANT Vol.6(No.3) 195-202, 2002

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Recently, as the range of mobile communication services is extended, the interference between adjacent base-stations is increased. Nowdays, on of the important factors causing interference is IMD(Inter-Modulation Distortion) problems. Not only active IMD but also passive IMD effects must be considered to design a CDMA system. In this study, we design and implement 7/16`` DIN connectors which have a various intensity of surface illumination, thickness and quality of plating material to analyze the effects of PIMD. And propose the methods for improving the PIMD characteristics: First, it is more profitable to use the metal which has good intensity of surface illumination where most of all electric currents passes through it. Secondly, we should plate metals more than 5 μm for RF energy enough to propagate in a medium. Thirdly, it is necessary to select a metal having high conductivity and specific heat to protect the aging phenomenon of plate material. And it is required to develop a new plating material to replace the current materials, such as the alloy of three components for cost reduction. We have to know that the plate which has intensity of surface illumination 6 S and the thickness of plating material 5 μm satisfy domestic PIMD specification (KTF) - 150 dBc, regardless of the plate material in case of 7/16`` DIN connector.

곽재민 Jae Min Kwak , 정해원 Hae Won Jung , 조성준 Sung Joon Cho , 이형호 Hyeong Ho Lee

DOI: JANT Vol.6(No.3) 203-210, 2002

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In this paper, the BER performance of IEEE 802.11a OFDM WLAN system is obtained by simulation and it is shown that the proposed modified channel estimation algorithm improves the channel estimation performance of the system. The wireless channel used in channel simulation includes AWGN and delay spread channel implemented by TDL model. At first, the performance of OFDM WLAN system according to data rate and coding rate defined in standard is evaluated in AWGN channel. Then, imperfect channel estimation in indoor wireless channel is considered. After the performance of conventional channel estimation scheme using only two long training symbols is evaluated, and that of proposed modified channel estimation scheme using additional 8 short training symbol is compared with it. From the simulation results, it is shown that modified channel estimation scheme provides reduced channel estimation error and improves the channel estimation performance due to noise averaging effect with the same preamble format as defined in specification.

박철현 Chul Hyun Park , 권용수 Yong Soo Kwon

DOI: JANT Vol.6(No.3) 211-222, 2002

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This paper describes the utility of satellite sensors of the missile defense system using the estimation theory. The inherent flight characteristics of the missiles give the limitations in the response time and the countermeasures. In this point, the early warning and surveillance satellites are important. Using the Extended Kalman Filter, it is analysed LPU and MLU in DSP and SBIRS satellites, and presented the quantitative uncertainties of state estimates of non-rotational DSP compare to the rotating one.

이성렬 Seong Real Lee , 김남성 Nam Sung Kim , 방효창 Hyo Chang Bang

DOI: JANT Vol.6(No.3) 223-230, 2002

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In this paper, we induced that the noise powers and bit error rate of direct detection receiver taking account of ISI (intersymbol interference) in the 2,000 km optical transmission system. And we evaluated the sensitivity in the vrious bit rate system. We verified that the proposed calculation method is applicable to the exact optical system. And we confirmed that the signal distortion due to both chromatic dispersion and nonlinear effects compensated by using of MSSI(Mid-Span Spectral Inversion) method, and yet the sensitivity of a higher bit rate system is reduced, because of the increase of ISI and then the decrease of the average receiving power, compared with a the lower bit rate system.

박제홍 Je Hong Park , 이우주 Woo Joo Lee , 임상석 Sang Seok Lim

DOI: JANT Vol.6(No.3) 231-240, 2002

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For a long time target maneuvers in tracking problem have been a difficult task to handle. In order to solve this problems, there have been various tracking techniques. In the development of a tracking filter for a maneuvering target, maneuver detection threshold plays a key role. However, no study of filter performance the varying maneuver detection threshold has been carried out so far. In stead, the maneuver detection have been chosen empirically. In this paper, the effect of detection threshold selection on the performance of the tracking filters was considered and the relationships between maneuvers and the detection threshold have been analyzed by simulation.

권순녀 Soon Nyu Kweon , 이윤현 Yun Hyun Lee

DOI: JANT Vol.6(No.3) 241-250, 2002

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This paper presents a way to maximize transmission efficiency and reception ability through transmission diversity technology, which can be adapted to wireless multimedia OFDM system. The presented method is a comparative analysis between a case wheere parameter α for time average is 0.3, 1 with consideration of channel presumption with two types of rms delayed spread, which is 50nsec, 150nsec, for the performance analysis of STTC(Space-Time Trellis Code) using time-space ciphering method appropriate for MIMO channel, and performance in the case where presumed channel value from long training column section is applied to according frame in a single frame. The result showed that BER brought SNR improvement of 1.0 dB in 10^3 when α was 0.3 than using only the long training column, and showed increase of general performance improvement for the sake of time average rather than the case without.

장원호 Won Ho Jang , 박주성 Joo Sung Park , 태재훈 Jae Hoon Tae , 이윤현 Yun Hyun Lee

DOI: JANT Vol.6(No.3) 251-257, 2002

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Design and characteristic improvement of existing folded dipole antenna is presented to adopt W-CDMA(1.885~2.170 ㎓) wideband antenna radiators. The antenna structure has +/- 45 degrees dual polarization. In order to overcome the narrow bandwidth and low gain characteristic typical of the microstrip antenna, double layered structure was employed. The antenna achieved below -20 ㏈ reflection coefficients each ports. -20 ㏈ of port isolation, above 7 dBi of gain, providing evidence that the proposed design can be used in the W-CDMA service frequency band antenna.

학회자료

DOI: JANT Vol.6(No.3) 258-258, 2002

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