• Title/Summary/Keyword: 공간 필터

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Development of 2-kW Class C Amplifier Using GaN High Electron Mobility Transistors for S-band Military Radars (S대역 군사 레이더용 2kW급 GaN HEMT 증폭기 개발)

  • Kim, Si-Ok;Choi, Gil-Wong;Yoo, Young-Geun;Lim, Byeong-Ok;Kim, Dong-Gil;Kim, Heung-Geun
    • The Journal of the Korea institute of electronic communication sciences
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    • v.15 no.3
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    • pp.421-432
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    • 2020
  • This paper proposes a 2-kW solid-state power amplifier (SSPA) developed by employing power amplifier pallets designed using gallium-nitride high electron mobility transistors, which is used in S-band military radars and to replace existing traveling-wave tube amplifier (TWTA). The SSPA consists of a high-power amplifier module, which combines eight power amplifier pallets, a drive amplifier module, a digital control module, and a power supply unit. First, the amplifier module and component were integrated into a small package to account for space limitations; next, an on-board harmonic filter was fabricated to reject spurious components; and finally, an auto gain control system was designed for various duty ratios because recent military radar systems are all active phase radars using the pulse operation mode. The developed SSPA exhibited a max gain of 48 dB and an output power ranging between 63-63.6 dBm at a frequency band of 3.1 to 3.5 GHz. The auto gain control function showed that the output power is regulated around 63 dBm despite the fluctuation of the input power from 15-20 dBm. Finally, reliability of the developed system was verified through a temperature environment test for nine hours at high (55 ℃) / low (-40℃) temperature profile in accordance with military standard 810. The developed SSPA show better performance such as light weight, high output, high gain, various safety function, low repair cost and short repair time than existing TWTA.

Improving Classification Accuracy of Motion Imaginary Electroencephalogram Using Mutual Information and Rare Learning (상호 정보와 희소 학습을 이용하여 동작 상상 뇌파의 분류 정확도 향상)

  • Lee, David;Park, Sang-Hoon;Lee, Hee-Jae;Lee, Sang-Goog
    • The Journal of Korean Institute of Information Technology
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    • v.15 no.8
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    • pp.67-74
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    • 2017
  • Brain-computer interface (BCI) is a technology that directly connects a human brain and a computer to control and manipulate the computer through electroencephalogram. The common spatial pattern (CSP) is the most famous method for extracting discriminative features from BCI based on motor imagery electroencephalogram. However, CSP is sensitive to the operational frequency band, and this operational frequency band is subject-specific. In this paper, we propose a method to extract subject-specific features based on mutual information and sparse learning. The proposed method divides the 4~40Hz band into 17 sub-bands using a fifth order Butterworth filter. Then, CSP is applied to each sub-band to extract CSP features. Thereafter, mutual information is used to select the four most discriminating feature sets from the CSP features and sparse learning was used to eliminate redundancy in the four pairs of features selected. Finally, support vector machine was used for learning and classification. The performance of the proposed method was evaluated using formally available BCI Competition III and IV. The proposed method showed higher average classification accuracy than the results of CSP, FBCSP and SFBCSP.

A Study On RTLS(Real Time Location System) Based on RSS(Received Signal Strength) and RSS Characteristics Analysis with the External Factors (외적요인에 따른 RSS 특성 분석과 이를 이용한 실시간 위치 추적 시스템 구현에 관한 연구)

  • Lee, Seung-Ho
    • Journal of IKEEE
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    • v.15 no.1
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    • pp.76-85
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    • 2011
  • In this paper, we analysed RSS characteristics by external factors and presented an efficient algorithm for real-time location tracking and its hardware system. The proposed algorithm enhanced the ranging accuracy using Kalman Filter based on the RSS DB. The location tracking system that consists of the tag, AP(Access Point), a data collector(Data Receiver) with IEEE 802.15.4(ZigBee) network environment, and location tracking application that reveal locations of each tag is implemented for the test environment. The location tracking system presented in this paper is implemented with MSP430 microprocessor manufactured by TI(Texas Instrument), CC2420 RF chipset and the location tracking application. With the results of the experiment, the proposed algorithm and the system can achieve the efficiency and the accuracy of location tracking with the average error of 19.12cm, and its standard deviation of 5.31cm in outdoor circumstance. Also, the experimental result shows that exact tracking of position in indoor circumstance cannot achieve because of vulnerable RSS with external circumstance.

Single Path Phase-only Security System using Phase-encoded XOR Operations in Fourier Plane (푸리에 영역에서의 위상 변조 Exclusive-OR 연산을 이용한 단일 경로 위상 암호화 시스템)

  • Shin, Chang-Mok;Cho, Kyu-Bo;Kim, Soo-Joong;Noh, Duck-Soo
    • Korean Journal of Optics and Photonics
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    • v.16 no.4
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    • pp.326-333
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    • 2005
  • Phase-only encryption scheme using exclusive-OR rules in Fourier plane and a single path decryption system are presented. A zero-padded original image, multiplied by a random phase image, is Fourier transformed and its real-valued data is encrypted with key data by using XOR rules. A decryption is simply performed based on 2-1 setup with spatial filter by Fourier transform for multiplying phase-only encrypted data by phase-only key data, which are obtained by phase-encoding process, and spatial filtering for zero-order elimination in inverse-Fourier plane. Since the encryption process is peformed in Fourier plane, proposed encryption scheme is more tolerant to loss of key information by scratching or cutting than previous XOR encryption method in space domain. Compare with previous phase-visualization systems, due to the simple architecture without a reference wave, our system is basically robust to mechanical vibrations and fluctuations. Numerical simulations have confirmed the proposed technique as high-level encryption and simple decryption architecture.

NEAR REAL-TIME IONOSPHERIC MODELING USING A RBGIONAL GPS NETWORK (지역적 GPS 관측망을 이용한 준실시간 전리층 모델링)

  • Choi, Byung-Kyu;Park, Jong-Uk;Chung, Jeong-Kyun;Park, Phil-Ho
    • Journal of Astronomy and Space Sciences
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    • v.22 no.3
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    • pp.283-292
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    • 2005
  • Ionosphere is deeply coupled to the space environment and introduces the perturbations to radio signal because of its electromagnetic characteristics. Therefore, the status of ionosphere can be estimated by analyzing the GPS signal errors which are penetrating the ionosphere and it can be the key to understand the global circulation and change in the upper atmosphere, and the characteristics of space weather. We used 9 GPS Continuously Operating Reference Stations (CORS), which have been operated by Korea Astronomy and Space Science Institute (KASI) , to determine the high precision of Total Electron Content (TEC) and the pseudorange data which is phase-leveled by a linear combination with carrier phase to reduce the inherent noise. We developed the method to model a regional ionosphere with grid form and its results over South Korea with $0.25^{\circ}\;by\;0.25^{\circ}$ spatial resolution. To improve the precision of ionosphere's TEC value, we applied IDW (Inverse Distance Weight) and Kalman Filtering method. The regional ionospheric model developed by this research was compared with GIMs (Global Ionosphere Maps) preduced by Ionosphere Working Group for 8 days and the results show $3\~4$ TECU difference in RMS values.

Sound Enhancement of low Sample rate Audio Using LMS in DWT Domain (DWT영역에서 LMS를 이용한 저 샘플링 비율 오디오 신호의 음질 향상)

  • 백수진;윤원중;박규식
    • The Journal of the Acoustical Society of Korea
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    • v.23 no.1
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    • pp.54-60
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    • 2004
  • In order to mitigate the problems in storage space and network bandwidth for the full CD quality audio, current digital audio is always restricted by sampling rate and bandwidth. This restriction normally results in low sample rate audio or calls for the data compression scheme such as MP3. However, they can only reproduce a lower frequency range than a regular CD quality because of the Nyquist sampling theory. Consequently they lose rich spatial information embedded in high frequency. The propose of this paper is to propose efficient high frequency enhancement of low sample rate audio using n adaptive filtering and DWT analysis and synthesis. The proposed algorithm uses the LMS adaptive algorithm to estimate the missing high frequency contents in DWT domain and it then reconstructs the spectrally enhanced audio by using the DWT synthesis procedure. Several experiments with real speech and audio are performed and compared with other algorithm. From the experimental results of spectrogram and sonic test, we confirm that the proposed algorithm outperforms the other algorithm and reasonably works well for the most of audio cases.

Signature-based Indexing Scheme for Similar Sub-Trajectory Retrieval of Moving Objects (이동 객체의 유사 부분궤적 검색을 위한 시그니쳐-기반 색인 기법)

  • Shim, Choon-Bo;Chang, Jae-Woo
    • The KIPS Transactions:PartD
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    • v.11D no.2
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    • pp.247-258
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    • 2004
  • Recently, there have been researches on storage and retrieval technique of moving objects, which are highly concerned by user in database application area such as video databases, spatio-temporal databases, and mobile databases. In this paper, we propose a new signature-based indexing scheme which supports similar sub-trajectory retrieval at well as good retrieval performance on moving objects trajectories. Our signature-based indexing scheme is classified into concatenated signature-based indexing scheme for similar sub-trajectory retrieval, entitled CISR scheme and superimposed signature-based indexing scheme for similar sub-trajectory retrieval, entitled SISR scheme according to generation method of trajectory signature based on trajectory data of moving object. Our indexing scheme can improve retrieval performance by reducing a large number of disk access on data file because it first scans all signatures and does filtering before accessing the data file. In addition, we can encourage retrieval efficiency by appling k-warping algorithm to measure the similarity between query trajectory and data trajectory. Final]y, we evaluate the performance on sequential scan method(SeqScan), CISR scheme, and SISR scheme in terms of data insertion time, retrieval time, and storage overhead. We show from our experimental results that both CISR scheme and SISR scheme are better than sequential scan in terms of retrieval performance and SISR scheme is especially superior to the CISR scheme.

Multi-step Ahead Link Travel Time Prediction using Data Fusion (데이터융합기술을 활용한 다주기 통행시간예측에 관한 연구)

  • Lee, Young-Ihn;Kim, Sung-Hyun;Yoon, Ji-Hyeon
    • Journal of Korean Society of Transportation
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    • v.23 no.4
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    • pp.71-79
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    • 2005
  • Existing arterial link travel time estimation methods relying on either aggregate point-based or individual section-based traffic data have their inherent limitations. This paper demonstrates the utility of data fusion for improving arterial link travel time estimation. If the data describe traffic conditions, an operator wants to know whether the situations are going better or worse. In addition, some traffic information providing strategies require predictions of what would be the values of traffic variables during the next time period. In such situations, it is necessary to use a prediction algorithm in order to extract the average trends in traffic data or make short-term predictions of the control variables. In this research. a multi-step ahead prediction algorithm using Data fusion was developed to predict a link travel time. The algorithm performance were tested in terms of performance measures such as MAE (Mean Absolute Error), MARE(mean absolute relative error), RMSE (Root Mean Square Error), EC(equality coefficient). The performance of the proposed algorithm was superior to the current one-step ahead prediction algorithm.

A Stereo Video Avatar for Supporting Visual Communication in a $CAVE^{TM}$-like System ($CAVE^{TM}$-like 시스템에서 시각 커뮤니케이션 지원을 위한 스테레오 비디오 아바타)

  • Rhee Seon-Min;Park Ji-Young;Kim Myoung-Hee
    • Journal of KIISE:Computer Systems and Theory
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    • v.33 no.6
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    • pp.354-362
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    • 2006
  • This paper suggests a method for generating high qualify stereo video avatar to support visual communication in a CAVE$^{TM}$-like system. In such a system because of frequent change of light projected onto screens around user, it is not easy to extract user silhouette robustly, which is an essential step to generate a video avatar. In this study, we use an infrared reflective image acquired by a grayscale camera with a longpass filter so that the change of visible light on a screen is blocked to extract robust user silhouette. In addition, using two color cameras positioned at a distance of a binocular disparity of human eyes, we acquire two stereo images of the user for fast generation and stereoscopic display of a high quality video avatar without 3D reconstruction. We also suggest a fitting algorithm of a silhouette mask on an infrared reflective image into an acquired color image to remove background. Generated stereo images of a video avatar are texture mapped into a plane in virtual world and can be displayed in stereoscopic using frame sequential stereo method. Suggested method have advantages that it generates high quality video avatar taster than 3D approach and it gives stereoscopic feeling to a user 2D based approach can not provide.

A Preliminary Research of Design and Operation of Riparian Buffer Zones for Reduction of Water Pollutants and Construction of Wildlife Habitat (수질정화 및 생태서식처 조성을 위한 수변완충지대 설계 및 운영 방안 기초연구)

  • Chung, Sang-Joon;Woo, Hyo-Seop;Oh, Jong-Min;Choi, I-Song;Ahn, Hong-Gyu
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.1073-1077
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    • 2006
  • 급속한 산업화로 인한 오염물질의 증가와 생물서식처의 감소는 수자원과 생태계를 위협하고 있다. 국내의 경우 수자원의 질을 개선하기 위해 '90년대 초부터 하수처리시설 등의 저감시설을 대폭 확충하였으나 현재까지 팔당호 등 주요상수원이 목표수질에 못 미치고 있으며 그 원인은 유입오염물질의 $22{\sim}37%$를 차지하는 비점오염원으로 지목되고 있다. 또한 생태.경관적 가치가 높은 수변지역은 각종 개발로 생물서식처가 급속도로 감소하여 종 다양성 보전 측면에서 대책마련이 시급한 실정이다. 이와 유사한 상황에 직면한 선진외국에서는 '하천회랑(river corridor)' 또는 '토양 및 생태시스템을 포함하는 수역과 육역의 점이(漸移)지대'를 의미하는 이른바 '수변완충지대(Riparian Buffer Zones)'의 오염정화 및 생태조성 효과 등의 연구를 통해 효율적 조성방안을 제시하고 있으며 다양한 형태로 현장에 적용하고 있다. RBZs의 일반적인 기능으로는, 유사나 오염물질의 여과 및 차단(필터링 효과), 영양염류의 저감, 하천변 식생을 통한 수자원의 정화 및 강턱의 안정화, 홍수로 인한 하천침식의 방지, 수변 생물 서식처 제공, 수변 그늘 제공에 의한 수온상승 방지, 심미 교육 위락 공간 제공 등이다. 본 연구에서는 외국의 RBZs(Riparian Buffer Zones)가이드라인을 참고하여 국내실정에 맞는 파일럿 규모의 시험완충지를 설계 및 조성하였다. 시험완충지는 남한강 연안에 초본류, 갈대류, 관목류, 자연식생, 혼합식생 등 5가지 'dry biotope'형태로 설치하여 1년간 계절별로 운영하였다. 또한 실험의 정량화와 다양한 조건변화를 위해 차수막, 위어, 유량.농도 조절장치, 라이시미터 등 보조시설을 설치하였고, 정기적인 모니터링을 실시하였다. 조사결과 외국사례를 살펴보면 RBZs의 적정 폭은 수질정화기능의 경우 $15{\sim}30m$, 생태서식처 기능은 최소 90m이상으로 제시되며, 시험완충지의 수질정화효과는 SS, T-N, T-P, TOC의 평균저감율이 각각 50%이상으로 나타났다. 식생모니터링 결과, 환삼덩굴 등 우점종의 잠식속도는 약 15일이며 갈대와 갯버들의 경우 우기시 인공목책호안과 동일한 침식방지 효과를 보이는 것으로 관찰되어 식생의 주기적인 모니터링과 지역 특성에 적합한 우점종 선정이 매우 중요한 것으로 판단된다.

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