• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 봄 학술발표회논문집
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• pp.119-124
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• 2000

The radar method is becoming one of the major nondestructive testing (NDT) techniques for concrete structures. Numerical modeling of electromagnetic wave is needed to analyze radar measurement results and to study the influence of measurement parameters on the radar measurements. Finite difference-time domain (FD-TD) method is used to simulate electromagnetic wave propagation through concrete specimens. Three concrete specimens with a 25 mm delamination embedded at 25 mm, 50 mm, and 75mm depth are modeled in 3-dimension. Also, thickness change of delamination and permittivity change are modeled.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 가을 학술발표회논문집
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• pp.18-23
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• 2000

The radar method is becoming one of the major nondestructive testing (NDT) techniques for concrete structures. Numerical modeling of electromagnetic wave is needed to analyze radar measurement results and to study the influence of measurement parameters on the radar measurements. Finite difference-time domain (FD-TD) method is used to simulate electromagnetic wave propagation through concrete specimens. Three concrete specimens with a 19.1 mm rebar embedded at 40 mm, 60 mm, and 80 mm depth are modeled in 3-dimension. As results, 2-D image processing scheme of modeling data has been developed and applied to the imaging of steel bars inside concrete.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2006년도 춘계종합학술대회
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• pp.223-227
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• 2006

밀리미터 레이더는 짧은 파장으로 근거리 접촉물을 정밀하게 측정할 수 있기 때문에 미래의 ITS 기술의 안전을 지원하는 핵심기술로써 대두되고 있다. 특히, 차량의 충돌방지용으로 밀리미터 레이더가 대두되며, 사용주파수는 $76\sim77GHz$가 이용되고 있다. 그러나 레이더는 반사에 의한 허상으로 오 신호가 발생할 수 있으며, 시스템간의 상호 간섭을 일으킬 수 있기 때문에 위험을 초래할 수 있다. 그러나 이러한 문제는 전파흡수체를 사용하여 제거할 수 있다. 따라서, 본 논문에서는 차량 충돌방지 레이더용 전파흡수체 개발을 위해 연구가 수행되었으며, 측정된 복소비유전율과 복소 비투자율을 이용하여 시뮬레이션한 결과를 토대로 차량 충돌방지 레이더용 전파흡수체를 제작한 결과 조성비가 Permalloy:CPE=70:30 wt%에서, 두께 1.4mm, $76\sim77$ GHz에서 전파흡수능 18 dB 이상을 획득하였다.

• 대한임베디드공학회논문지
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• 제18권6호
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• pp.319-325
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• 2023

In this study, we proposed a method for hyperparameter optimization in the building and training of a deep learning model designed to process point cloud data collected by a millimeter-wave radar system. The primary aim of this study is to facilitate the deployment of a baseline model in resource-constrained IoT devices. We evaluated a RadHAR baseline deep learning model trained on a public dataset composed of point clouds representing five distinct human activities. Additionally, we introduced a coarse-to-fine hyperparameter optimization procedure, showing substantial potential to enhance model efficiency without compromising predictive performance. Experimental results show the feasibility of significantly reducing model size without adversely impacting performance. Specifically, the optimized model demonstrated a 3.3% improvement in classification accuracy despite a 16.8% reduction in number of parameters compared th the baseline model. In conclusion, this research offers valuable insights for the development of deep learning models for resource-constrained IoT devices, underscoring the potential of hyperparameter optimization and model size reduction strategies. This work contributes to enhancing the practicality and usability of deep learning models in real-world environments, where high levels of accuracy and efficiency in data processing and classification tasks are required.

• Journal of information and communication convergence engineering
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• 제4권3호
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• pp.114-117
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• 2006

In this paper, we fabricated the EM wave absorber for 94 GHz radar sensors using Permalloy of magnetic material with chlorinated polyethylene (CPE), and S-parameter was measured. The complex relative permittivity and permeability are calculated by the measured data. Absorption abilities are simulated according to different thickness of the EM wave absorbers, and the EM wave absorber was manufactured based on the simulated design. Simulated and measured results agree very well. As a result, we developed the EM wave absorber with the thickness of 1.15 mm which has an absorption ability of 18 dB at 94 GHz.

• ETRI Journal
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• 제41권2호
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• pp.262-269
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• 2019

This paper introduces a low-cost, high-performance mmWave antenna array module at 77 GHz. Conventional waveguide transitions have been replaced by 3D CPW-microstrip transitions which are much simpler to realize. They are compatible with low-cost substrate fabrication processes, allowing easy integration of ICs in 3D multi-chip modules. An antenna array is designed and implemented using multilayer coupled-fed patch antenna technology. The proposed $16{\times}16$ array antenna has a fractional bandwidth of 8.4% (6.5 GHz) and a 23.6-dBi realized gain at 77 GHz.

• 한국전자파학회지:전자파기술
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• 제4권3호
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• pp.3-10
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• 1993

전파흡수체의 전파흡수능 측정방법은 기본적으로 다양한 마이크로파 측정법이 이용될 수 있지만, 레이다용 전파흡수체의 경우, 전파의 주파수가 높기 때문에 파장이 짧아서 측정오차가 큰 문제점이 있다. 따라서, 지금까지는 $20mm\Phi$동축관 및 구형도파관을 이용한 재료정수측정법과 전파흡수능측정기법에 관하여 검토하여 왔다. 본 논문에서는 그동안 실험실적으로 설계하여 온 X-Barn Radar용 전파홉수체를 실용의 상태에 가까운 반사 전력법에 의하여 그 성능을 예비평가하고, 실제의 target를 제작하여 X-Band Radar로 실장실험한 결과에 관하여 보고한다.

• 한국초전도ㆍ저온공학회논문지
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• 제24권1호
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• pp.29-33
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• 2022

Recently, development of a cryogenic fluids storage tank for storing or transporting liquid hydrogen is actively in progress. In cryogenic fluids storage tanks, hydrogen evaporates due to the extreme temperature difference inside and outside the tank. As the mass of the cryogenic fluids changes with continuous vaporization, the fluids level also changes. Therefore, there is need for a method of accurately measuring the level change in the storage tank. In the case of general cryogenic fluids, it is difficult to accurately measure the level because the dielectric constant is very low. As a method of measuring cryogenic fluids level with low dielectric constant, it can be used an Millimeter wave (MM wave) FMCW radar sensor. However, the signal sensitivity is very weak and the level accuracy is poor. In this paper, the signal sensitivity is improved by designing the horn lens antenna of the existing 80 GHz FMCW radar sensor. Horn lens antenna is fabricated by FDM/SLA type 3D printer according to horn and lens characteristics. The horn is used to increase the signal gain and the lens improves the signal straightness. This makes it possible to measure the level of cryogenic fluids with a low dielectric constant.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권4호
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• pp.1209-1223
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• 2022

Blood pressure is one of the key physiological parameters for determining human health, and can prove whether human cardiovascular function is healthy or not. In general, what we call blood pressure refers to arterial blood pressure. Blood pressure fluctuates greatly and, due to the influence of various factors, even varies with each heartbeat. Therefore, achievement of continuous blood pressure measurement is particularly important for more accurate diagnosis. It is difficult to achieve long-term continuous blood pressure monitoring with traditional measurement methods due to the continuous wear of measuring instruments. On the other hand, radar technology is not easily affected by environmental factors and is capable of strong penetration. In this study, by using machine learning, tried to develop a linear blood pressure prediction model using data from a public database. The radar sensor evaluates the measured object, obtains the pulse waveform data, calculates the pulse transmission time, and obtains the blood pressure data through linear model regression analysis. Confirm its availability to facilitate follow-up research, such as integrating other sensors, collecting temperature, heartbeat, respiratory pulse and other data, and seeking medical treatment in time in case of abnormalities.

• 대한전자공학회논문지TC
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• 제43권9호
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• pp.1-5
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• 2006

본 논문에서는 ITS 기반의 기본 센서인 차량 충돌방지 레이더의 허상으로 인한 오신호 또는 시스템간의 상호 간섭을 방지하기 위하여 전파흡수체를 설계 및 제작하였다. 먼저 도전손실 재료인 카본과 지지재인 CPE를 이용하여 조성비별 전파흡수체 샘플을 제작하고, 측정데이터로부터 최적의 조성비가 카본:CPE=20:80 wt% 임을 확인하였다. 그리고 이 샘플로부터 재료정수인 복소비유전율을 계산하여 시뮬레이션을 하였으며, 시뮬레이션 결과를 토대로 전파흡수체를 실제작하여 전파흡수능을 비교 분석한 결과 시뮬레이션값과 측정값이 잘 일치하였다. 결과적으로 조성비 카본:CPE=20:80 wt%로 전파흡수체 두께 2 mm 주파수 범위 $76{\sim}77$ GHz에서 전파흡수능 20 dB 이상으로 전파흡수체를 개발하였다.