• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.8
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• pp.114-125
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• 2014

In a conventional sonar system, which uses LFM signal for detecting targets with varying speed, the results of multiple LFM Doppler correlators are aligned and the maximum alined result are selected as a test cell for detecting targets. As the number of the LFM Doppler correlators are increased for accurate target detection, as the required computational complexity and the memory are also increased. This fact makes it difficult to implement the accurate LFM target detector. In this paper, we propose a new fast target detection which is robust for the variation of target speed. Because the proposed method uses the summation of alined results of large numbers of LFM Doppler correlators, the proposed method increase SNR and provide robust SNR for the variation of target speed. And the proposed method can provide very fast target detection by implementing the process, the summation of alined results of large numbers of LFM Doppler correlators, as one summation filter.

• The Journal of the Acoustical Society of Korea
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• v.26 no.3
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• pp.129-135
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• 2007

In this paper. we propose a prewhitening method for the km reverberation to enhance the target signal. The proposed algorithm uses the dechirping method which inversely compensates the frequency chirp rate of LFM and transforms the LFM reverberation to have stationary frequency property in each data block. Also, using the left and right adjacent beam signals as reference signals. we model frequency response of each data block by AR coefficients. From these coefficients, we implement inverse filter and prewhiten the LFM reverberation of the center beam efficiently.

• The Journal of the Acoustical Society of Korea
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• v.20 no.8
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• pp.58-66
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• 2001

In this paper, a computationally efficient time delay and doppler estimation algorithm is proposed for active sonar with Linear Frequency Modulated (LFM) signal. To reduce the computational burden of the conventional estimation algorithm, an algebraic equation is used which represents the relationship between the time delay and doppler in cross-ambiguity function of the LFM signal. The algebraic equation is derived based on the Fast maximum Likelihood (FML) method. Using this algebraic relation, the time delay and doppler are estimated with two 1-D search instead of the conventional 2-D search. The estimation errors of the proposed algorithm are analyzed for various SNR's. The simulation result demonstrates the good performance of the proposed algorithm.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.11a
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• pp.1237-1239
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• 2023

본 논문에서는 Linear Frequency Modulation(LFM)을 이용하여 실해역에서 실험을 진행하였다. LFM 이란 시간에 따라 주파수가 변화하는 Chirp 신호를 전송하는 통신 기법이며 성능 분석을 위해 대한민국의 한강, 서해, 남해에서 각각 실험을 진행하였다. LFM 신호의 중심 주파수는 34kHz 대역폭은 1kHz로 설정하여 실험을 진행하였으며 채널 환경 분석을 위한 5초 길이의 Tone 신호를 함께 송·수신 하였다. 실험 결과 세 곳의 실험 포인트 모두에서 송·수신 신호 간의 뚜렷한 상호상관 결과를 확인할 수 있었다.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.4
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• pp.258-264
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• 2015

The first 77 GHz transceiver that applies a heterodyne structure-based linear frequency modulation-frequency shift keying (LFM-FSK) front-end module (FEM) is presented. An LFM-FSK waveform generator is proposed for the transceiver design to avoid ghost target detection in a multi-target environment. This FEM consists of three parts: a frequency synthesizer, a 77 GHz up/down converter, and a baseband block. The purpose of the FEM is to make an appropriate beat frequency, which will be the key to solving problems in the digital signal processor (DSP). This paper mainly focuses on the most challenging tasks, including generating and conveying the correct transmission waveform in the 77 GHz frequency band to the DSP. A synthesizer test confirmed that the developed module for the signal generator of the LFM-FSK can produce an adequate transmission signal. Additionally, a loop back test confirmed that the output frequency of this module works well. This development will contribute to future progress in integrating a radar module for multi-target detection. By using the LFM-FSK waveform method, this radar transceiver is expected to provide multi-target detection, in contrast to the existing method.

• Fisheries and Aquatic Sciences
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• v.24 no.3
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• pp.109-120
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• 2021

Protein hydrolysates and krill meal (KM) are used as protein sources in aquafeeds. The study was conducted to examine the supplemental effects of shrimp protein hydrolysates (SH) or KM in a high-plant-protein diet for red seabream (Pagrus major). A fish meal (FM)-based diet (40%) was considered as the high-FM diet (HFM) and a diet containing 25% FM and soy protein concentrate, in the expense of FM protein from HFM diet, was considered as the low fish meal (LFM) diet. Two other experimental diets (SH and KM) were prepared by including SH and KM into LFM diet at 5% inclusion levels in exchange of 5% FM from the LFM diet. A feeding trial was conducted for fifteen weeks using triplicate group of fish (Initial mean body weight, 8.47 ± 0.05 g) for a diet. Growth performance and feed efficiency of fish were significantly enhanced by HFM, KM and SH supplemented diets over those of fish fed LFM diet. Interestingly, these parameters of fish fed SH diet showed better performance than KM and HFM groups. Liver IGF-I expression of fish fed SH diet was comparable to HFM group and higher than KM and LFM diets. Protein digestibility of SH diet was significantly higher than KM, HFM, and LFM diets. Dry matter digestibility of SH diet was comparable to HFM diet and significantly higher than KM and LFM diets. Nitro blue tetrazolium and superoxide dismutase activities of HFM, SH and KM groups were significantly elevated than the LFM group and SH diet increased catalase and glutathione peroxidase activities of fish compared to KM and LFM groups. Hemoglobin level and hematocrit of fish fed SH and KM diets were significantly higher than LFM group. A diet containing 20% FM with KM is comparable to a HFM diet which contains 40% FM for red seabream. SH can be used to replace FM from red seabream diet down to 20% and fish performance can be improved better than a diet containing 40% FM. Overall, it seems that SH is more effective ingredient in red seabream diet compared to KM.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.8
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• pp.97-103
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• 2014

Signal processing technique of linear frequency modulation-frequency shift keying (LFM-FSK) waveform has been introduced for rear view radars of an automobile. LFM-FSK waveform consists of two sequential stepped frequency waveforms with some frequency offset, and thus, can be used to generate inverse synthetic aperture radar (ISAR) images of rear view target of an automobile. However, ISAR images can often be blurred due to inter-pulse phase errors. To resolve this problem, one-dimensional (1-D) entropies of high resolution range profiles (HRRP) are minimized with the help of particle swarm optimization (PSO). The searching space used in PSO is adaptively adjusted by the use of information on the target's velocity obtained from LFM-FSK waveforms. Simulation results show that the proposed method can generate well-focused ISAR images.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.3
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• pp.300-308
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• 2023

This study aimed to evaluate the utilization of low fish meal (LFM) diet and black soldier fly (BSF) Hermetia illucens meal supplementation in LFM diet as a fish meal (FM) replacer or functional additive for juvenile olive flounder Paralichthys olivaceus. Three LFM diets were prepared to contain 30, 25, and 20% FM, respectively (designated as F30, F25, and F20). Three BSF diets were prepared by adding 2.0, 2.5, and 3.0% BSF in the LFM diets, respectively (designated as F30B2.0, F25B2.5, and F20B3.0). A total of 540 fish (initial mean body weight: 22.3±0.01g) were randomly distributed into 18 tanks (240 L) in triplicate groups and fed the experimental diets twice daily for 12 weeks. Results showed that there were no significant differences in the growth performance, feed utilization and survival among all the groups. Lysozyme activity significantly increased in F30B2.0 and F25B2.5 groups compared to their respective LFM groups. Total immunoglobulin was significantly higher in F30 group than in F20 group. Anti-protease and myeloperoxidase activities were significantly higher in F30B2.0 group than in F20 group. Innate immunity gradually decreased with decreasing FM level in all the groups. BSF supplementation significantly improved immunity compared to their respective LFM diets. Therefore, BSF could be used as an immuno-stimulant supplement in LFM diets for P. olivaceus.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.1
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• pp.35-40
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• 2000

Teflon-like fluorocarbon thin film was deposited on various substrates by vapor deposition using PFDA (perfluorodecanoic acid). The fluorocarbon films were characterized by static/dynamic contact angle analysis, VASE (Variable-angle Spectroscopic Ellipsometry) and AFM/LFM (Atomic/Lateral Force Microscopy). Based on Lewis Acid/Base theory, the surface energy ($S_{E}$) of the films was calculated by the static contact angle measurement. The work of adhesion (WA) between de-ionized water and substrates was calculated by using the static contact data. The fluorocarbon films showed very similar values of the surface energy and work of adhesion to Teflon. All films showed larger hysteresis than that of Teflon. The roughness and relative friction force of films were measured by AFM and LFM. Even though the small reduction of surface roughness was found on film on $SiO_2$surface, the large reduction of relative friction farce was observed on all films. Especially the relative friction force on TEOS was decreased a quarter after film deposition. LFM images showed the formation of "strand-like"spheres on films that might be the reason far the large contact angle hysteresis.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.3
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• pp.540-545
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• 2013

The Fractional Fourier transform, as a generalization of the classical Fourier Transform, was first introduced in quantum mechanics. Because of its simple and useful properties of Fractional Fourier transform in time-frequency plane, various research results in sonar and radar signal processing have been introduced and shown superior results to conventional method utilizing Fourier transform until now. In this paper, we applied Fractional Fourier transform to sonar signal processing to detect and separate the overlapping linear frequency modulated signals. Experimental results show that received overlapping LFM(Linear Frequency Modulation) signals can be detected and separated effectively in Fractional Fourier transform domain.