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이승학,천종훈,박종안,Rhee, Seung-Hak,Chun, Jong-Hun,Park, Jong-An 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.11A
In this paper, we have designed a RFID reader receiver system for improving the performance of the passive Tag based 9$'908.5{\sim}914MHz'$ RFID reader, and analyzed the system performance according to the frequency, the reader, and tag properties. The commercial receive system causes a loss in sensitivity because of 24 capacitors and 6 inductors. So we have designed an improved system using a circulator, LNA and a SAW filter. The experimental results show that the use of a circulator to separate the Tx/Rx paths eliminates interference, the LNA improves the sensitivity of the Rx module and SAW filter eliminates the noise and spurious components in the received signal. 본 논문에서는 수동형 태그 기반 908.5~914MHz RFID 리더기의 수신 감도를 개선하고자 수신부에 서큘레이터, LNA 그리고 SAW필터를 사용하는 개선된 수신부 시스템을 설계하였다. 그리고 시뮬레이션을 통하여 동작 주파수 및 리더기와 태그 상호간 특성에 따른 수신부 성능을 분석하였다. 분석결과 상용 시스템은 24개의 캐패시턴스(C)와 6개의 인덕터(L)를 사용함으로써 감도 손실을 가져왔으나, 본 연구에서는 설계된 시스템은 서큘레이터 사용에 의해 상호 간섭을 최소화할 뿐만 아니라 LNA 사용으로 수신 감도를 크게 향상시키는 결과를 얻을 수 있었다. 또한 SAW 필터에 의해 송 수신부 간섭을 최적화시킴으로써 시스템 감도가 더욱 개선되었음을 확인하였다.
Image retrieval using local frequency maxima of histogram based color Correlogram
Gwang-won Kang(강광원),Seung-hak Rhee(이승학),Jong-hun Chun(천종훈),Seung-jin Park(박승진),Jong-an Park(박종안) 한국정보기술학회 2008 한국정보기술학회논문지 Vol.6 No.1
Color histograms is a very useful technique used for retrieving and indexing images in a content-based image retrieval (CBIR) system. They provide a graphical representation of global color distribution of an image. However, the histograms are not robust to major changes in the object appearance. There might also be a case where histogram might give same or similar representation for different images, which depends upon the color distribution in the images. Correlograms are used for efficient indexing of images. They not only extract the color distribution of pixels in images like color histogram, but also extracts the spatial information of pixels in the images. The characteristic of the intensity Correlogram are taken into account for extracting the spatial information as well as the distribution of color pixels greatly attracts the researcher for content based image retrieval. In this paper, we propose the image bin (histogram value divisions) separation technique followed by extracting maxima of frequencies and plotting a Correlogram. At first, the histogram is calculated for an image. After that, it is subdivided into four equal bins. Each bin is subdivided into four more bins and for every such subdivision the maxima of frequencies is calculated. This information is stored in the form of a Correlogram. The distance between Correlogram of the query image and the corresponding Correlogram of database images is calculated. The proposed algorithm is tested on a database comprising a large number of images and gives promising results.