• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.3
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• pp.327-335
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• 2011

A study on the RCS of a self-manufactured active transponder, which has a manually adjustable RCS, for SAR(Synthetic Aperture Radar) external calibration and image analysis at X-band is presented in this paper. The RCS of the active transponder was comparably analyzed using the lab-test and the COSMO-SkyMed SAR system, and also precisely analyzed the difference between the adjusted and estimated RCSs. A maximum RCS of the designed and manufactured active transponder is 60 dBsm. The active transponders with 60 dBsm and the adjusted RCS of 40 dBsm were measured using the single target calibration technique(STCT) and 2D target scanning technique(2DTST). And the extracted RCS using power-spill integration technique in a SAR image was compared with the measured RCS of active transponder. The comparison results show that the measured and extracted RCSs are 59.7 dBsm, 40.2 dBsm and 57.3 dBsm, 39.2 dBsm, respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.957-960
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• 2006

In this paper, we studied the location estimation algorithm of a spatial 3 dimension which extend the location estimation algorithm of a plane 2 dimension in 2.45GHz band RTLS(Real time location system). We used TDOA scheme which need not a time of transmission information of the tag and estimated 3 dimension coordinates. Also, estimated intersection of hyperbolic curve to X, Y coordinate of the tag at 2D coordinates searching area, $300m\times300m$ and LOS propagation environments. And, we estimated Z coordinate ultimately using X, Y coordinate. The location estimation algorithm of a spatial 3 dimension satisfies the RTLS specification requirement, 3m radius accuracy. From the result, we confirm that the location of tag which similar to actual coordinate in the case to an ideal received offset. However, we verified that the location of tag which escapes from a radius 3m within error range when received offset increased. Therefore, as the future work we are consider enhanced location accuracy of a spatial 3 dimension in RTLS system which using the decrease scheme of reader offset or the discriminate scheme of the estimation location.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.483-483
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• 2013

Latral Composition Modulation (LCM)으로 성장한 InP/GaP 초격자(Superlattice)의 선편광된 광발광(Photoluminescence) 특성을 저온(5 K)에서 측정하였다. LCM 기법은 z-축 방향으로 InP와 GaP를 단층 초격자(monolayer supperlattice)로 성장하는 과정에서 strain에 의해 x-y 평면으로 초격자가 형성되는 특별한 경우이다. 이렇게 성장된 LCM 초격자의 경우 In-rich 영역과 Ga-rich 영역이 교차로 성장되는 구조를 가지며 가전자대역(valence band)에서 무거운 양공과 가벼운 양공의 band mixing 이 일어나게 되어 선평광된 발광특성을 가진다. 우리는 저온 발광실험에서 In-rich 영역과 Ga-rich 영역의 재결합에 의해 나타나는 두 개의 독립된 전이 피크를 측정하였다. 이 두 피크는 [110] 방향의 편광에서 발광 강도가 최대치를 가지며 [1-10] 방향에서 최소값을 가짐을 보였다. 이때 전이 에너지의 경우 [110] 방향에서 [1-10] 방향으로 편광이 바뀔 때 Ga-rich 영역의 전이의 경우 적색편이를 나타낸 반면 In-rich 영역의 경우 청색편이를 보이는 현상을 발견하였다. 이러한 상반된 편이 현상은 서로 다른 3족 물질의 영역에 따라 격자 상수가 바뀌며 tensile strss와 compressive stress에 따른 가전자 대역의 band mixing 변화에 기인하는 것으로 여겨진다.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2007.05a
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• pp.99-101
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• 2007

비종관 관측자료인 기상위성 및 레이더 분석자료에서 위성영상에서 볼 수 있는 서해남부 해상의 스콜라인 형태의 강한 대류운을 무안-진도 레이더 반사도에 의한 수평 및 연직 구조로 살펴보았는데 특히 발달한 대류운 영역이 보다 상세한 반사도 차이로 나타나고, 40 dBZ 이상 강한 반사도 셀이 고도 6km, 20km 정도의 수평규모를 갖는 여러 대류운시스템이 합쳐진 다중세포시스템으로 구성되어 있음을 알 수 있었다. 또한 연구용 X-대역 무안 레이더 반사도 분포를 보면 사이트 주면에 강한 dBZ의 대류운이 자리하고 있어 발달한 강수입자에 의한 감쇄효과 때문에 북서방향과 남서방향의 강한 대류운들이 약하게 잘못 관측되고 있음을 볼 수 있었지만 S-대역 진도 레이더는 발달한 강수 입자에 크게 영향을 받지 않고 고유의 강한 반사도를 제대로 관측하고 있음을 알 수 있었다. 이와 같이 태풍에 의한 직${\cdot}$간접적인 호우, 장마전선의 활성화에 따른 집중호우를 동반하는 중규모대류운시스템에 대해 정확히 정량적으로 판단할 수는 없지만, 관측자료 분석을 통해 중규모대류운시스템을 발달${\cdot}$유지시킬 수 있는 기구의 존재 가능성을 체계적으로 이해하는데 많은 도움이 되었다. 본 연구 결과를 바탕으로 레이더 반사도와 3차원 바람장 그리고 마이크로강우레이더와 광학강우강계에 의한 연직 구름계와 순간적으로 발생하는 강수특성 등 섬세하고 다양한 비종관 관측자료를 이용하여 집중호우를 유발하는 중규모대류운시스템의 강수 구조와 특성 분석 및 예측에 활용될 수 있으리라 기대된다.

• Information and Communications Magazine
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• v.16 no.10
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• pp.112-124
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• 1999

본 논문에서는 FTTC/VDSL (Fiber-to-the-Curb/Very High-speed Digital Subscriber Line) 전송시스템의 개발동향과 ANSI, ETSI, ITU등의 표준화 위원회에서 현재 진행중인 VDSL 시스템의 표준화 작업에 대해 기술하였다. 특히, POTS (Plain Old Telephone Service), BA-ISDA(Basic Access Integrated Services Digital Network), HDSL(High-rate Digital Subscriber Line), SDSL (Single-pair HDSL), ADSL(Asymmetric Digital Subscriber Line) 등의 다양한 xDSL (Digital Subscriber Line) 서비스들에서 발생하는 NEXT (Near-end Crosstalk)/FEXT (Far-end Crosstalk)와 같은 crosstalk를 최소화하기 위해 제안된 VDSL시스템의 주파수 대역과 PSD (Power Spectral Density) mask에 관해 설명하고, 순방향(down-stream) 채널과 역방향(upstream) 채널의 데이터 전송률이 대칭적인 VDSL전송시스템과 비대칭적인 VDSL 전송시스템 간의 주파수대역의 호환성 문제, RFI(Radio Frequency Interference) ingress/egress 문제의 해결 방안에 관해 기술하였다. 또한, 현재 VDSL Coalition과 VDSL Alliance 간에 논의 중인 VDSL 전송시스템의 변복조 방식에 관한 표준화 작업과정 및 순방향과 역방향에 할당될 band 개수에 따른 시스템 성능의 장단점 등에 관해 살펴보았다. 끝으로 현재 국내에서 개발되고 있는 FTTC/VDSL 전송시스템의 전체구조를 요약하고, 네트워크에서 가입자쪽으로 순방향 데이터 전송에 사용된 51.84 Mb/s 19-CAP (Carrierless Amplitude/Phase Modulation) 전송시스템과 가입자 댁내에서 네트워크 방향으로 역방향 데이터 전송에 사용된 1.62 Mb/s QPSK (Quadrature Phase Shift Keying) burst-mode TDMA (Time Division Multiple Access) 전송시스템 등의 동작 원리 및 구조를 기술하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.4
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• pp.382-389
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• 1997

We present the results on the applicability of the polycrystalline AIN thin films for a surface acoustic wave filter operating at 800 MHz frequency. The films show the FWHM of 3 .deg. from th X-ray rocking curve, which indicates that the c-axis of the films is pre- ferentially oriented along the growth direction. The fabricated band pass filters exhibit the center frequency of 865 MHz with 3dB band-width of 45 MHz. From the measured frequency response, the electro-mechanical coupling constant of 0.8% and the SAW velocity of 5,709 m/s are obtained. Thus, we conclude that the sputtered AIN films are feasible for the fabrication of uper UHF band SAW filters.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11B
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• pp.1595-1599
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• 2001

In this paper, we have desired and implemented of ASK modulator MMIC operating at 5.8 GHz for OBE used in AGPS(Automatic Gate Passing System). The proposed ASK modulator MMIC was implemented to apply a single supply voltage of 3 V to the drain in order to decrease ACP(Adjacent Channel Power). As a result, it is exhibits a broad linear modulation range from 0.7 V to 3 V and an On/off characteristic over 40 dB. The layouts of ASK modulator MMICs was designed and fabricated by using ETRI 0.57m MESFET library The chip size was 1.0mm $\times$x1.0mm.

• The Journal of the Acoustical Society of Korea
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• v.19 no.2
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• pp.33-39
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• 2000

We have studied to obtain the frequency characteristics of the Surface Acoustic Wave(SAW) bandpass filter, having low shape factor, it's interdigital transducer(IDT) was formed on the 35° Y-cut X-propagation Quartz substrate and was evaporated by Aluminium. And then, we performed computer-simulation by a simulator. And, we can design that the apodization weighted type IDT as an input transducer of the filter and the withdrawal weighted type IDT as an output transducer of the filter from the results of our computer-simulation. Also, we have employed that the number of pairs of the input and output IDT are 2200 pairs and 1000pairs, respectively and used the Kaiser-Bessel window function in order to minimize the effect of ripple. And, while the width and the space of IDT's finger are 6㎛ m and 5.75㎛, respectively and we could obtain the resonable results when the IDT thickness was 6000Å in consideration of the ratio of SAW's wavelength, and IDT aperture is 2mm. Frequency response of the fabricated SAW bandpass filter has the property that the center frequency is about 70MHz, shape factor is less than 1.3, bandwidth at the 1.5dB is probably 1.3MHz, out-band attenuation is almost -45dB, insertion loss is 19dB and ripple in the width of bandpass is 1dB approximately. Therefore, these frequency characteristics of the fabricated SAW bandpass filter are agreed well with the designed values.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.8
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• pp.41-46
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• 2012

A quadrature voltage controlled oscillator(QVCO) for X-band is presented in this paper. The QVCO has fabricated in Charted $0.13{\mu}m$ CMOS process. The QVCO consists of two cross-coupled differential VCO and two differential buffers. The QVCO is controlled by 4 bit of capacitor bank and control voltage of varactor. To have a linear quality factor of varactors, voltage biases of varactors are difference. The QVCO generates frequency tuning range from 6.591 GHz to 8.012 GHz. The phase noise is -101.04 dBc/Hz at 1MHz Offset when output frequency is 7.150 GHz. The supply voltage is 1.5 V and core current 6.5-8.5 mA.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.5
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• pp.860-867
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• 2009

In this paper, we designed the array antenna for FMCW radar in X - band frequency, and we chose stacked structure for improvement of narrow bandwidth. The array antenna is implemented on the circuit board which is relative permittivity 2.33 and the stacked patchs are designed on the circuit board which is relative permittivity 4.6. A Foam which has a similar permittivity of air is added to keep the particular gap between array antenna and the stacked patch. The result of array antenna has characteristics that a half-power beam width is $10.6^{\circ}$ and antenna gain is 18.70 dBi and bandwidth is 1.25GHz at the design frequency of 9GHz. The result of the array antenna with the stacked structure has that the half power beam width is $15.17^{\circ}$ and the antenna gain is 15.85dBi and bandwidth is 2GHz. It is needed to improve the antenna gain as keeping bandwidth in same level.