다수의 2차원 단층영상으로부터 3차원 영상을 합성하기 위한 Angular 스펙트럼의 적용

양훈기,이상이,김은수 한국통신학회 1996 韓國通信學會論文誌 Vol.21 No.7

This paper presents the evaluation of an angular spectrum-based method used to calculate scattering pattern of a three-dimensional object modelled as a collection composed of vertical sectional two-dimensional images. This is done via comparing a proposed method with two existing methods, i.e., a Fresnel hologram method and a ray-tracing method, in terms of computatioal complexities and reconstructed results. Maathematical derivations for each methods are reviewed and implementing procedures are described in detail, along with the amount of computaions required from the implementation point of view, rather than from the mathematical point of view. We show simulation results in which the Fresnel holoram method dose not exhibit promising results although it requires the least computation. Moreover, it is also shown that the proposed method, even with much less computational requirement than the ray-tracing method, produces good performances asmuch as the ray-tracing method does.

Incoherent Processing of ISAR data for Moving Targets' Detection

양훈기 광운대학교 신기술연구소 1997 신기술연구소논문집 Vol.26 No.-

본 논문은 SNR이 상당히 낮은 ISAR 데이터로 부터 인코히어런트한 처리를 거쳐 이동표적을 효과적으로 검출할 수 있는 방법을 제시한다. 제시된 방법은 위치와 시간의 함수인 ISAR데이터를 공간주파수 및 시간주파수 함수로 변환한 후 유한개의 시간주파수 함수에서의 공간주파수 함수를 인코히어런트하게 더해줌으로써 이동표적 성분을 검출한다. 주어진 ISAR 시스템 환경에서 수신신호의 공간주파수 평면에서의 대역폭을 제시하며, 인코히어런트하게 더하기 전에 요구되는 전처리과정을 설명한다. 사용되는 공간 주파수 신호가 많아 질수록 수신신호의 variance가 감소하여 표적성분이 검파되는 이유를 확률 통계적으로 설명하며, 마지막으로 수신주파수를 충분히 사용할때의 false alarm 및 miss 확률을 유도한다. An efficient incoherent method to detect moving targets’ signitures out of heavily corrupted ISAR data is presented. The proposed method, after converting a two-dimensional space-time received signal into a two-dimensional spatial frequency-temporal frequency domain, exploits a finite number of spatial frequency functions extracted from some specific temporal frequencies. Selected spatial frequency functions are incoherently added together such that the moving targets’ signitures are revealed out of clutter with lowered variance. The bandwidth of the targets’ signitures in the spatial frequency domain are determined and the pre-processing procedure required prior to incoherent addition is described. It is shown that from the probabilitic /statistic point of view, as the number of functions used for addition increases, the targets’ signitures should become more dominent. Finally, for a situation where a sufficient number of functions are added, a false-alarm and miss rates are derived.

디지털 홀로그래픽 3차원 입체 영상 통신에 관한 연구 ( A Study on Digital Holographic 3-D Image Communication )

양훈기,김은수 한국통신학회 1997 한국통신학회 공개발표회 및 토론회 Vol.- No.-

SAR 신호처리 알리고즘의 개발 및 구현

양훈기 光云大學校 1995 論文集 Vol.24 No.-

The far field radiation pattern of a radar resembles a spherical wave. The existing SAR inverse methods are based on approximations for the spherical radiation pattern of the radar, e. g., the Fresnel approximation(stripmap-mode SAR), or the planewave approximation (spotlight-mode SAR). These methods fail in the case of high resolution imaging of a large object area. In this paper, we present a SAR system model and an inversion method based on a spatial Fourier decomposition. It is shown that this spectral decomposition transforms nonlinear phase functions of the target's spatial domain and synthetic aperture domain into linear phase functions. The performances of the proposed method implemented using simulated data are compared with those of the abovementioned approximation based methods.

Inverse SAR에서 속도를 모르는 움직이는 물체의 이미징 알고리즘

양훈기,김은수 한국통신학회 1994 韓國通信學會論文誌 Vol.19 No.5

본 논문은 Inverse SAR를 이용하여 속도를 모르는 움직이는 물체의 영상 이미지를 얻는 이미징 알고리즘을 제시하였고 실제 데이터를 알고리즘에 적용되었다. 실제 데이터는 stepped-frequency 변조된 레이더 신호를 송신하였고 수신된 데이터는 sampling rate이 충분하지 않으나 reference 신호를 mixing 시켜 unaliased 되게 만든 후 interpolation 에 의해서 해결하였다. 알고리즘을 적용시키는데 요구되는 물체의 속도는 subaperture processing 방법에 의해서 얻어졌으며 얻어진 속도에 의해서 squint-mode SAR geometry 로 변환한 후 최근에 제시된 approximation 이 없는 이미징 알고리즘을 사용하여 최종적으로 이미지를 얻게 되었다. 또한 ISAR가 데이터를 송수신 하는 동안 물체의 속도가 변하는 경우 이것을 보상하는 방법을 제시하였다. This paper presents Inverse SAR imaging algorithm for a unknown velocity target and a real ISAR data is processed and applied to the algorithm. The real ISAR data is obtained by transmitting a number of pulse modulated by a stepped-frequency method and the received data are undersampled. We present a method applicable for the case of a undersampled data base. In this method, the original echoed signal is mixed with a reference signal to make it unaliased, followed by being interpolated. Target`s velocity required for the algorithm is estimated via subaperture processing and after the coordinate transformation into squint-mode SAR with the estimated velocity, a recently proposed SAR/ISAR imaging algorithm derived without any approximation is utilized to produce the output image. We also propose an ISAR image scheme that is usable when a target changes its velocity during ISAR data acquisition time.

적은 STAP 데이터의 공간주파수-도플러 평면 변환을이용한 공분산행렬 추정

양훈기 한국전기전자학회 2023 전기전자학회논문지 Vol.27 No.1

Performance of a STAP(space-time adaptive processing) algorithm highly depends on how closely the estimatedcovariance matrix(CM) resembles the actual CM by the interference in CUT(cell under test). A STAP has 2dimensional data structure determined by the number of array elements and the number of transmitting pulses andboth numbers are generally not small. Thus, to meet the degree of freedom(DOF) of the CM, a huge amount oftraining data is required. This paper presents an algorithm to generate virtual training data from small receiveddata, via converting them into the data in spatial frequency-Doppler plane. We theoretically derive where theclutter exist in the plane and present the procedure to implement the proposed algorithm. Finally, with thesimulated scenario of small received data, we show the proposed algorithm can improve STAP performance. STAP(space-time adaptive processing) 알고리즘의 성능은 CUT(cell under test) 내의 간섭에 대한 공분산 행렬 추정의 정확도가 결정적 역할을 한다. STAP 데이터는 일반적으로 많은 배열 소자 및 사용된 다수의 송신 펄스에 의해 결정되는 2차원 데이터구조를 가지고 있다. 그러므로 공분산 행렬 추정의 정확도를 높이기 위해서는 매우 많은 트레이닝 데이터가 요구된다. 본 논문에서는 수신된 적은 개수의 데이터를 공간주파수-도플러 평면으로 변환한 후 가상의 트레이닝 데이터를 생성하는 알고리즘을 제시한다. 클러터 점유 위치를 이론적으로 유도하며 이에 근거해서 가상 트레이닝 데이터 생성 절차를 제시하고 STAP 시뮬레이션을 통해서제시된 알고리즘이 STAP 성능을 개선할 수 있음을 보인다.

실시간 디지털 홀로그램 합성을 위한 새로운 접근 방법 ( A New Approach for a Real-time Synthesis of Digital Hologram )

양훈기,이상이,김동영,김은수 한국통신학회 1995 한국통신학회 학술대회논문집 Vol.14 No.1

디지틀 홀로그램에서 샘플링 조건 완화를 위한 홀로그램 Segmentation

양훈기,류치연,김은수 대한전자공학회 1998 電子工學會論文誌, D Vol.d35 No.8

This paper presents a new method to synthesize a digital hologram that meets the resolution of a currently manufactured LCD while capable of displaying a 3-D object. That is accomplished by segmenting a hologram, resulting in relaxed sampling constraint. We show that the segmentation of a hologram enables us to utilize the planewave approximation and, unlike in a holographic stereogram, it does not require projection process, but directly takes fourier transform of horizontally sliced 2-D images that constitute a 3-D object, which makes it possible to reconstruct a higher resolution image with depth information. We also show that proposed hologram contains data significantly smaller than the conventional hologram does, which is quite useful for constructing wide-viewing hologram. Finally, simulation results obtained by both methods are compared.

모바일 기기를 위한 NTSC, PAL, SECAM ?오 인코더의 설계

양훈기,강봉순,김주현 한국통신학회 2005 韓國通信學會論文誌 Vol.30 No.11

홀로그래픽 영상 암호화 및 디코딩 기법

양훈기,정대섭,김은수 대한전자공학회 1996 전자공학회논문지-A Vol.33 No.12

This paper presents a new security verification technique based on an image encryption by a white noise image that serves as an encryption key. In the proposed method that resembles holographic process, the encryption process is executed digitally using FFT routine which gives chances for separating corruptive noise from reconstructed primary image The encoded image thus obtained is regarded as an nterference pattern caused by two lightwaves transmitted through the primary image and the white noise image. The decoding process is executed optically and in real-tiem fashion where lightwave transmitted through the white noise image illuminates the encrypted card.