• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.4
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• pp.437-446
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• 2018

This paper describes the real-time logic implementation of orthogonal matching pursuit(OMP) algorithm for compressive sensing digital receiver. OMP contains various complex-valued linear algebra operations, such as matrix multiplication and matrix inversion, in an iterative manner. Xilinx Vivado high-level synthesis(HLS) is introduced to design the digital logic more efficiently. The real-time signal processing is realized by applying dataflow architecture allowing functions and loops to execute concurrently. Compared with the prior works, the proposed design requires 2.5 times more DSP resources, but 10 times less signal reconstruction time of $1.024{\mu}s$ with a vector of length 48 with 2 non-zero elements.

• The Magazine of the IEIE
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• v.23 no.10
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• pp.38-52
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• 1996

본 원고에서는 원격탐사용으로 사용되는 레이다 중에서 가장 많이 사용되는 Scatterometer에 대해 소개하였다. SAR는 주로 넓은 지역의 레이다 영상을 얻는데 사용되는 소위 영상레이다로서, 기본 구성품은 일반적인 레이다와 크게 다를 바 없으며 거의 모든 부분에서 현재의 state-of-the-art를 크게 벗어나는 요구사항은 없다고 판단된다. 단지 아주 작은 분해능(수십cm정도)을 실시간으로 요구할 때에는 막대한 계산량으로 인한 신호처리에서의 병목 현상을 적절히 해결해야 한다. 본 원고에서는 여러 가지의 SAR 신호처리 방식을 소개하였으며 본 대학에서 수행한 간단한 실험에 적용시킨 결과를 보였다. 또한 현재 많이 발표되고 있는 Interferometric SAR에 대해 간단히 소개하였으며, 마지막으로 레이다 영상으로부터 표적의 제반 특성을 추출하는 inversion algorithm을 개발하거나 기타 여러 연구에 사용될 수 있는 차량 탑재형 Scatterometer에 대해 소개하였다. 본 대학에서 개발중인 POPOS가 완성되면 지금까지 측정되거나 발표된 적이 없는 한국 특유의 표적이나 경작물들의 산란 특성($\sigma^{\circ}$)을 측정할 수 있으며, 또한 현재 관심의 대상이 되고 있는 GPEN 또는 FOPEN 등의 연구에도 크게 도움이 될 수 있으리라 기대된다.

• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.6
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• pp.313-319
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• 2019

Finite field operations have played an important role in error correcting codes and cryptosystems. Recently, the necessity of efficient computation processing is increasing for security in cyber physics systems. Therefore, efficient implementation of finite field arithmetics is more urgently needed. These operations include addition, multiplication, division and inversion. Addition is very simple and can be implemented with XOR operation. The others are somewhat more complicated than addition. Among these operations, multiplication is the most important, since time-consuming operations, such as exponentiation, division, and computing multiplicative inverse, can be performed through iterative multiplications. In this paper, we propose a multiplexer based parallel computation algorithm that performs Montgomery multiplication over finite field using redundant basis. Then we propose an efficient multiplexer based semi-systolic multiplier over finite field using redundant basis. The proposed multiplier has less area-time (AT) complexity than related multipliers. In detail, the AT complexity of the proposed multiplier is improved by approximately 19% and 65% compared to the multipliers of Kim-Han and Choi-Lee, respectively. Therefore, our multiplier is suitable for VLSI implementation and can be easily applied as the basic building block for various applications.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.4
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• pp.55-62
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• 2002

FRLGC(Fiber Ring laser Gain Clamped) EDFA Is demonstrated for an automatic gain control in hi-directional ADM(Add Drop Multiplexer) node configuration. Specifically, we investigate hi-directional characteristics of noise figure. Assuming a hi-directional small signal input, noise figures for forward or backward signal input are calculated using average inversion algorithm, according to the propagating directions and lasing wavelengths of a compensating signal. The operating condition of FRLGC-EDFA may be optimized with a backward lasing and short lasing wavelength in the aspect of hi-directional noise figure characteristics.

• Investigative Magnetic Resonance Imaging
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• v.19 no.1
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• pp.19-30
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• 2015

Purpose: A new compressed sensing technique by iterative truncation of small transformed coefficients (ITSC) is proposed for fast cardiac CINE MRI. Materials and Methods: The proposed reconstruction is composed of two processes: truncation of the small transformed coefficients in the r-f domain, and restoration of the measured data in the k-t domain. The two processes are sequentially applied iteratively until the reconstructed images converge, with the assumption that the cardiac CINE images are inherently sparse in the r-f domain. A novel sampling strategy to reduce the normalized mean square error of the reconstructed images is proposed. Results: The technique shows the least normalized mean square error among the four methods under comparison (zero filling, view sharing, k-t FOCUSS, and ITSC). Application of ITSC for multi-slice cardiac CINE imaging was tested with the number of slices of 2 to 8 in a single breath-hold, to demonstrate the clinical usefulness of the technique. Conclusion: Reconstructed images with the compression factors of 3-4 appear very close to the images without compression. Furthermore the proposed algorithm is computationally efficient and is stable without using matrix inversion during the reconstruction.

• Ocean and Polar Research
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• v.24 no.3
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• pp.197-205
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• 2002

Total magnetic field and high-resolution bathymetric data were collected over nine seamounts to the northwest of the Marshall Islands in the western Pacific. Magnetic parameters including inclination and declination were calculated from the magnetic anomalies using inversion algorithm of Plouff (1976), and a corresponding paleomagnetic pole was determined with the magnetic parameters. The paleomagnetic poles determined in this study were compared with the previous apparent polar wander path (APWP) of Pacific plate. Most seamounts of the study area have normal polarity. The study reveals that all nine seamounts in the study area formed in the southern hemisphere during the Cretaceous based on their comparison with the APWP of Pacific plate. The ages estimated from paleomagnetic poles can be divided by age into three groups: the oldest (OSM1 and OSM3), middle age (OSM2, OSM4, and 6-2), and the youngest (OSM5-1, 5-2, 5-3, and 6-1). The fermer two groups and the latter seem to be coincident with two distinct pulses of Cretaceous volcanic activity (115-90 Ma and 83-65 Ma). As a whole the seamounts at southwest of the study area are older than at those northeast.

• Journal of Korea Society of Digital Industry and Information Management
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• v.8 no.4
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• pp.115-120
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• 2012

In multi-user multi-input multi-output (MU-MIMO) system, zero forcing beamforming (ZFB) is regarded as a realistic solution for transmitting scheme due to its low complexity and simple structure. However, ZFB shows a significant performance degradation when channel matrix has large condition number. In this case, the largest singular value of the channel inversion matrix has a dominant effect on transmit power. In this paper, we propose a perturbation method for reducing an effect of the dominant singular value. In the proposed algorithm, channel inverse matrix is first decomposed by SVD for the transmit signal to be expressed as a combination of singular vectors. Then, the transmit signal is perturbed to reduce the coefficient of the singular vector corresponding to the largest singular value. When a number of transmit antennas is 4, the simulation results of this paper shows that the proposed method shows 8dB performance enhancement at 10-3 uncoded bit error rate (BER) compared with conventional ZFB. Also, the simulation results show that the proposed method provides a comparable performance to Tomlinson-Harashima Precoding (THP) with much lower complexity.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.5
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• pp.51-64
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• 1991

In this paper, an attempt is made to analyze the impulsive stress directly underneath the concentrated impact point for a supported square plate by using the three-dimensional dynamic theory of elasticity and the potential theory of displacement (stress function) on the supposition that the load, F$_{*}$0 sin .omega.t, acted on the central part of it. The results obtained from this study are as follows: 1. The impulsive stress cannot be analyzed directly underneath the acting point of concenrated impact load in privious theories, but can be analyzed by using the three-dimensional dynamic theory of elasticity and the potential theory of displacement. 2. Theorically, with increasing the pulse width of applied load, it was possible to clarify that the amount of stress in the point of concentrated impact load was increased and that of stress per unit impulse was decreased. 3. The numerical inversion of laplace transformation by the use of the F.F.T algorithm contributes the reduction of C.P.U time and the improvement of the accuracy or results. 4. In this paper recommended, it is found that the approximate equation of impact load function P (.tau.) = A.tau. exp (-B.tau.), and P (.tau.) =0.85A exp (-B.tau.) sinC.tau. could actually apply to all impact problem. In compared with the experimental results, the propriety of the analytical method is reasonable.

• Geophysics and Geophysical Exploration
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• v.1 no.3
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• pp.155-160
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• 1998

EM tomography technique has been developed. The algorithm used the extended Born approximations for forward modeling and reconstructed a conductivity image by a smoothness constraint least squares inversion method. Observed data, the vertical components of secondary magnetic fields, were simulated with the 3-D integral equation code. The results showed that the location of anomalous body could be imaged very well, but conductivity of the body was lower than real one and the vertical resolution was much higher than the horizontal resolution.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.113-118
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• 2008

Among the geophysical methods, Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) comprise the most promising techniques in resolving buried archaeological structures in urban territories. In this work, two case studies which involve an integrated geophysical survey employing the surface three dimensional (3D) ERT and GPR techniques, in order to archaeologically characterize the investigated areas, are presented. Totally more than 4000 square meters were investigated from the test field sites, which are located at the centre of two of the most populated cities of the island of Crete, in Greece. The ERT and the GPR data were collected along dense and parallel profiles. The subsurface resistivity structure was reconstructed by processing the apparent resistivity data with a 3D inversion algorithm. The GPR sections were processed with a systematic way applying specific filters to the data in order to enhance their information context. Finally, horizontal depth slices representing the 3D variation of the physical properties were created and the geophysical anomalies were interpreted in terms of possible archaeological structures. The subsequent excavations in one of the sites verified the geophysical results, enhancing the applicability of ERT and GPR techniques in the archaeological exploration of urban territories.