디지털 信號의 實時間 處理

許道根 원광대학교 공업기술개발연구소 1981 工業技術開發硏究誌 Vol.1 No.-

This paper describes the algorithm that reduces the operation time of the digital signal processing and studies digital system which processes the digital signals in real time using this algorithm. As the studied results, the operation time enhances at 2.5~3.0 times than that of implementation of TTL I.C. Then we can change digital system characteristics without hardware changes.

CDMA 채널을 통한 영상 전송에 대한 연구

허도근,김용욱 한국통신학회 1997 韓國通信學會論文誌 Vol.22 No.11

본 논문에서는 영상정보를 효과적으로 전송할 수 있는 CDMA(Code Division Multiple Access) 영상 통신 시스템에서 요구되는 영상압축기법, 가변길이 PN 코드, 이들 기법을 적용할 수 있는 두 가지 채널 모형을 제시하고 그 성능을 비교 분석하였다. 원영상을 2차원 DCT(Discrete Cosine Transform)로 압축하고 변환계수를 압축률 O.84bit/pel로 최적 양자화기로 양자화시킨다. CDMA 전송을 위해 각각 5개의 채널과 4개의 채널로 구성된 채널 모델 1과 2를 채택하고 체바세프 맵과 같은 가변길이 PN코드로 대역확산시킨다. 채널 모델 l과 2에 대하여 평균 PN 코드 길이가 각각 44.4와 26.7 칩 일 때 분산이 1.75인 가우시안 잡음 환경하에서 이들 모델을 통해 수신된 영상은 송신한 영상과 시각적으로 동일함을 보였다. 따라서 모델 2가 모델 1이나 고정길이 PN 코드를 사용하는 채널 모델과 비교할때 채널 효율변에서 우수함을 보였다. This paper proposes a compression technique of image data, a variable length PN code and channel models which are required in CDMA communication system. It also analyzes their performances. Original images is compressed by 2-D DCT and its coefficients are quantized by optimal quantizer at compression rate 0.84bit/pel. Channel model 1 and 2 which are composed of 5 and 4 channels respectively are employed to be used in CDMA. Such a situation forces us to empoly variable length PN code, such as Chebyshev map for spread spectrum system. When average PN code length of model 1 and 2 is 44.4 and 26.7 chips respectively, the received image through these models under Gaussian noise with variance 1.75 is visually of the same quality as the transmitting image. Thus, the model 2 appears to be better in channel efficiency, comparing with channel model 1 and channel model which uses fixed length PN code.

디지털 필터의 설계와 구성 ( A DESIGN AND CONSTRUCTION OF DIGITAL FILTER )

허도근,진용옥,이대영 대한전자공학회 1980 대한전자공학회 학술대회 Vol.1980 No.1

컴퓨터를 利用한 디지탈 필터 設計

許道根 원광대학교 공업기술개발연구소 1984 工業技術開發硏究誌 Vol.4 No.-

This paper proposes the algorithm which designed the digital filter with computer aided design method for it to achieve a specified amplitude response. The program to execute this algorithm is listed to design 16-order digital filter with FORTRAN 77 language. The amplitude response of 2-order low pass digital filter which is designed by this program conforms to the specified amplitude response. This proposed algorithm is applicable without regard to a sort and order number of digital filter.

웨이브렛 패킷 변환을 이용한 대역 확산 코드에 관한 연구

허도근,정상연 원광대학교 공업기술개발연구소 1999 工業技術開發硏究誌 Vol.19 No.-

The recent commercial DS/SS CDMA, in which PN code is used as spreading code, accesses more users than FDMA or TDMA. As this system has 1.2288 Mchip/sec of long PN code, it takes long time for receiver to acquire and track PN code. A spreading code is proposed in this paper to resolve this problem. The proposed spreading code is designed by inverse wavelet packet transform of bin whose one element is 1 and others are 0. It has shown that correlation performance of the proposed spreading code is better than that of PN code and its BER is improved comparing with PN code. As its length is 1/8 of that of PN code and the effect of channel bandwidth is improved by 8 times of that of DS/SS CDMA.

방열판의 나사구멍 유무와 형태 식별 시스템에 관한 연구

허도근,심우성,김용욱 원광대학교 공업기술개발연구소 1996 工業技術開發硏究誌 Vol.16 No.-

In this paper, the visual system for recognition of type and existence of holes on the radiation-fin is realized as one of the FA application, using the property of light reflection which depends on the roughness of the holes, A image of radiation-fin is converted a binary image, and its hole regions are segmented from background and position data of hole regions are detected by the proposed segmentation algorithm. The existence of hole is checked by comparing hole regions in the test image with them in the reference image. The type of holes is classified by counting number of pixels in the hole region which depends on the roughness of the holes.

EREC 기반의 계층적 적용과 양방향 탐색에 의한 에러 복원 향상

허도근,김태주 원광대학교 공업기술개발연구소 2001 工業技術開發硏究誌 Vol.21 No.-

Bit erros in variable length codes cause synchronization loss. Loss of block synchronization produces the worst image degradation. Even an error of a single bit in block synchronization may result in data to be placed in wrong positions by spatial shifts, Error resilient coding reduces the redundancy due to channel coding and yet protects against error propagation. The EREC(Error Resilient Enoogy Coding) algorithm increases resilience and provides graceful degradation of errors by reordering the variable length codes into fixed length slots of data. Although the EREC algorithm enhances error resilience immensely, it has two disadvantages of redundancy and computational efficiency. In this paper, in order to improve the conventional EREC algorithm, the hierarctlical synchronization techruque and the bi-directional search process to determine the offset are used. As a result, show the loss of block less and the value of PSNR more than the conventional EREC algorithm. In the speed-up of search stage of the effectively applied EREC algorithm over of the conventional EREC algorithm, it is observed to 1.5 ~ 2.0.

트렐리스의 제로 상태 종료를 위한 가변 종료 인터리버

허도근,김용욱 원광대학교 공업기술개발연구소 2000 工業技術開發硏究誌 Vol.20 No.-

As the final state of the constructional encoder of Turbo code is different due to the feedback property of RSC(recursive systematic convolution) code and the existence of interleaver, in order to terminate Trellis in zero states, tail bits are required as many as the number of the memory of each encoders and the constructional Trellis is terminated separately Therefore, in this thesis, a variable termination interleaver, capable of terminating Trellis of two constructional encoders in zero states at the same time only with the tail bits as many as the number of memories terminating the first constructional encoder in zero states and handling variable frame such as interleavers recommended in IMT-2000 Standard, is proposed and then the properties are evaluated as compared to the conventional self-termination interleavers in sizes of frames.

한글 Pattern의 Subpattern 分離 方法에 關한 硏究

許道根 원광대학교 공업기술개발연구소 1981 工業技術開發硏究誌 Vol.1 No.-

Decomposition of Han-guel Pattern into basic subpattern is an important and interesting problem in Han-guel pattern recognition. Our approach to variable decomposition is a decomposition of Han-guel into basic subpattern by detecting 6-cfaracter form of Han-guel and being varied of Han-guel by detected character form. Further computer simulation result of recognition of 6-character form and decomrosition of Han- guel pattern into basic subpattern is showed.

자소 분리에 의한 한글 인식에 관한 연구

허도근,심우성 원광대학교 공업기술개발연구소 1995 工業技術開發硏究誌 Vol.15 No.-

It is difficult for computer to recognize Hangul characters becauae they are composed of several letters and the letters are joined together in some characters. To recognize the characters, characters are classified as six types known as 6-type of Hangul, and letters of the classified characters are segmented according to 6-type of character, and the segmented letters are recognized using a neural network. The neural network for type classification and character recognition is constructed as multi-layer. Inputs of the neural network are 4-direction vectors which are extracted from the mesh of the normalized character. The neural network is learned by the training rule of back propagation and descending epsilon algorithm to increase the learning speed and classification rate in the character classification and is learned by the back propagation algorithm in the character recognition. The type of character is classified completely in 1-type and 2-type and classification errors occur in the other four types. The most of recognition errors occur in 5-type and 6-type. It has been shown that classification rate is 96.5% and recognition rate is 93.5%.