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데이터 도움 방식의 효율적인 디지털 위성 방송 초기 주파수 추정회로 설계
박장웅(Jang Woong Park),선우명훈(Myung Hoon Sunwoo) 한국통신학회 2009 韓國通信學會論文誌 Vol.34 No.3
본 논문은 위성방송 표준인 DVB-S2 (Digital Video Broadcasting - Second Generation)의 복조기 설계에서 중요한 부분 중의 하나인 초기 주파수 추정 회로를 효율적으로 설계하는 방법을 제안한다. DVB-S2에서 초기 주파수 오차는 심볼 전송률의 20%에 해당하며 심볼 전송률이 25Msps일 경우 ±5MHz에 달한다. 이와 같이 큰 초기 주파수 오차를 추정하기 위해서는 추정 범위가 넓은 알고리즘이 요구된다. 본 논문에서는 데이터 도움 방식의 알고리즘들을 분석하고 성능 비교한 결과 M&M (Mengali & Moreli) 알고리즘이 낮은 SNR에서 우수한 추정 성능을 보여줌을 확인하였다. M&M 알고리즘을 적용한 기존의 주파수 추정 회로는 하드웨어 복잡도가 높기 때문에 자기 상관기와 역 탄젠트기의 수를 줄임으로서 전체 초기 주파수 추정기의 하드웨어 복잡도를 낮추는 방법을 제안한다. 제안된 구조는 기존의 구조에 비해 하드웨어 복잡도가 약 64.5%정도 감소하였으며 Xilinx Virtex II FPGA 검증 보드를 이용하여 제안된 구조를 검증하였다. This paper proposes an efficient initial frequency estimator for Digital Video Broadcasting-Second Generation (DVB-S2). The initial frequency offset of the DVB-S2 is around ±5MHz, which corresponds to 20% of the symbol rate at 25Msps. To estimate a large initial frequency offset, the algorithm which can provide a large estimation range is required. Through the analysis of the data-aided (DA) algorithms, we find that the Mengali and Moreli (M&M) algorithm can estimate a large initial frequency offset at low SNR. Since the existing frequency estimator based on M&M algorithm has a high hardware complexity, we propose the methods to reduce the hardware complexity of the initial frequency estimator. This can be achieved by reducing the number of autocorrelators and arctangents. The proposed architecture can reduce the hardware complexity about 64.5% compared to the existing frequency estimator and has been thoroughly verified on the Xilinx Virtex II FPGA board.
증상이 있는 담낭결석 환자에서 내시경적역행성담도조영술의 필요성에 관한 연구
이진,김동준,박철희,김용범,주상언,계세협,임창재,박우정,곽상택,장웅기,유재영 대한소화기내시경학회 1997 Clinical Endoscopy Vol.17 No.3
Background/Aims: Laparoscopic cholecystectomy(LC) has become the new therapeutic gold standard in uncomplicated symptomatic gallbladder stone. However, some patients with gallstones may be associated with bile duct stones or other biliary pathology. LC is not ideal for removal and evaluation of biliary duct stones even with advocated techniques. Although ERCP is the best way to demonstrate the biliary tree, ERCP is an invasive procedure that may causes complications. The aim of this study was to predict the neeessity for ERCP and to determine the indication of ERCP before LC using noninvasive methods of biliary tree associated liver biochemistry(LB) parameters and sonography. Methods: 270 symptomatic gallbladder stone patients were studied by both sonography and LB including total bilirubin, alkaline phophatase, r-glutamyltransferase and amylase. All patients were performd ERCP for evaluation of biliary tree pathology, Patients who were already found to have either tumors or bile duct stones on sonography were excluded. Patients were classified into normal and dilated biliary tree groups by sonographic findings, normal and abnormal LB groups, negative and positive ERCP groups. Positive ERCP were defined by bile duct stones, tumors, stricture and idiopathic common bile duct dilatation over 11 mm. Results: 1) There were positive ERP findings in 30.4% of all patients. 2) The male to female ratio was 1 : 2, and the patients of positive FRCP group(58.9 12.0) were significantly(p=0.000) older than negative group(52.7 13.1). 3) There was bile duct dilatation in 39.3% of patients by sonography. Bile duct dilatation on sonography had an 66.0% positive predictablity, 85.3% senstivity and 80.6% specificity for ductal pathology on FRCP. 4) There was abnormal LB kn 53.0% of patients. A single abnormal LB equated to a 46.2% positive predictablity, 80.5% sensitivity and 59.0% specificity for ductal pathology on ERCP. S) In patients with Math normal sonography and LB, 96.0% of patients had a negative ERCP study. Conclusion: FRCP is not necessary before LC for patients with symptomatic gallbladder stones who have both a normal biliary tree on sonograplty and normal LB. But, a patient with either a dilated bile duct on sonography or an abnormal LB does require ERCh study.