• KIEE International Transactions on Electrophysics and Applications
• /
• 제3C권6호
• /
• pp.224-229
• /
• 2003

An ultra high frequency (UHF) coupler possessing ultra wide band (UWB) characteristics ranging from hundreds of MHz to several GHz is desirable for the detection of the partial discharge (PD) pulses because the pulses propagate with rise time shorter than one nanosecond in a gas-insulated substation (GIS). Thus, the authors have proposed a log-periodic antenna for GIS PD detection. Various parameters of the coupler such as frequency bandwidth, coupler gain, radiation pattern, and coupler geometry were considered throughout the simulations. The experiments for the detection characteristics of the coupler were carried out in the mock-up GIS chamber. The results indicated that the detection characteristics of the coupler are dependent on the installation angle of the coupler, the position of the coupler in the hand hole and the existence of the spacer.

• Journal of electromagnetic engineering and science
• /
• 제16권4호
• /
• pp.206-209
• /
• 2016

This letter proposes a reconfigurable directional coupler that uses a variable impedance mismatch reflector to achieve high isolation characteristics in the antenna front end. The reconfigurable coupler consists of a directional coupler and a single-pole four-throw (SP4T) switch with different load impedances as a variable load mismatch reflector. Selection of the load impedance by the reflector allows cancellation of the reflected signal due to antenna load mismatch and the leakage from the input to isolation port of the directional coupler, resulting in high isolation characteristics. The performance of the proposed architecture in separating the received (Rx) signal from the transmitted (Tx) signal in the antenna front end was verified by implementing and testing the reconfigurable coupler at 917 MHz for UHF radio-frequency identification (RFID) applications. The proposed reconfigurable directional coupler showed an improvement in the isolation characteristics of more than 20 dB at the operation frequency band.

• 한국항행학회논문지
• /
• 제27권4호
• /
• pp.417-422
• /
• 2023

본 논문은 broadside 슬롯 결합선로를 이용하여 여러 구조의 3-dB 결합기를 구현하여 이것의 특성을 분석하였다. Tandem 구조의 이상적인 결합기는 첫 번째 와 두 번째 결합기의 연결부의 반사계수와 고립 계수가 모두 0임을 전제로 해석한다. 그러나 대부분의 결합기는 반사계수와 고립 계수가 0이 아니므로 이 경우에 결합기의 특성이 어떻게 변화 되는가를 S-파라미터 종속접속 계산 방법을 이용하여 확인하였다. 이와 같은 특성이 나오는 것을 확인하기 위하여 중심 주파수 2 GHz에서 broadside 슬롯 결합선로를 이용하여 1단 그리고 tandem 구조의 2단 그리고 3단으로 3-dB 결합기를 제작하였고, 제작된 결합기의 연결 부분의 반사 계수와 고립 계수가 0이 아님으로 인하여 측정된 결합기 특성이 열화되는 것을 확인하였다.

• 국제학술발표논문집
• /
• The 10th International Conference on Construction Engineering and Project Management
• /
• pp.10-17
• /
• 2024

Rebar lap splice is the most commonly used at construction sites because it does not require any additional equipment or labor's skills. Rebar lap splice has high construction costs because they require approximately 15% more rebar due to the overlap length. To solve these problems of rebar lap splice, mechanical rebar coupler was developed. Mechanical rebar coupler has a strong bonding force, helping to keep the structure safe even during earthquakes. In addition, mechanical rebar coupler is suitable for modular construction and easy to construct, so the construction period can be shortened. And mechanical rebar coupler can reduce the amount of rebar compared to other joint methods, thereby reducing CO2 emissions. Despite these advantages, the use of mechanical rebar couplers is not widespread except in some developed countries. This is because the types and characteristics of mechanical rebar couplers vary widely, making it difficult for construction engineers to choose. Existing research has only been conducted on mechanical rebar couplers in terms of structural experiments. And there is no research that classifies and analyzes the shapes of rebars. Hence, it should be analyzed the characteristics of mechanical rebar couplers in terms of construction methods for each shape. Therefore, the objective of this study is a basic study on comparative analysis of the characteristics and performance of different types of mechanical rebar coupler for sustainable built environment. The most efficient mechanical rebar coupler was derived for each construction site environment.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2015년도 추계학술대회
• /
• pp.68-70
• /
• 2015

4단자 커플러 회로는 입력 단자, 격리 단자와 두 개의 출력 단자로 구성된다. 입력 단자와 격리단자에 신호가 입력하면 입력하는 신호의 세기 및 위상 특성에 의해 두 개의 출력 단자의 출력 신호의 세기와 위상이 결정된다. 본 논문에서는 대표적인 4단자 커플러 회로인 브랜치라인 하이브리드 커플러와 링-하이브리드 커플러를 이용하여 두 개의 입력 단자의 입력 신호 특성에 따른 출력 신호 특성을 분석하였다. 또한, 분석한 신호를 바탕으로 브랜치라인 커플러와 링-하이브리드 커플러의 새로운 이용 방법에 대해 살펴 보았다.

• 한국기계가공학회지
• /
• 제20권2호
• /
• pp.66-71
• /
• 2021

A hydraulic quick coupler is a component used to easily connect or disconnect pipes or hoses that transfer high pressure fluid without leakage in various mechanical devices. In this study, to obtain an optimal design of a 3/8" hydraulic quick coupler, the effect of different shapes of the internal piston on the internal flow characteristics of the coupler was analyzed and evaluated through numerical analysis based on computational fluid dynamics. Subsequently, the optimal shape design of the internal piston was obtained by comparing the flow characteristics results such as velocity distribution, temperature distribution, and the pressure drop of the hydraulic quick coupler.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제51권5호
• /
• pp.204-212
• /
• 2002

In order to improve the reliability of high voltage rotating machines, it is necessary to understand the breakdown mechanism of stator windings. Especially partial discharge(PD) inception and growth are important in stator winding insulation. Recently, many research on the diagnosis of stator winding insulation for large rotating machines have been developed since the 1970s. Capacitive couplers have been the most widely used sensor for on-line partial discharge detection in rotating machines. This paper deals with the electrical on-line monitor characteristics of ceramic coupler(CC) which has been developed to continuously measure the PD activity in operating high voltage motor stator windings on site. We investigated the electrical characteristics(PD quantity, breakdown voltage and frequency response) to develop CC. This paper presents frequency characteristics and laboratory test result to compare conventional 80([F] epoxy-mica coupler(EMC) and 105[pF] CC for PD measurement with 6.6㎸ model stator windings.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 C
• /
• pp.1619-1622
• /
• 2001

Recently many researches on the diagnosis of stator winding insulation for large rotating machines have been developed sine the 1970s. Capacitive coupler has been the most widely used sensor for on-line partial discharge(PD) in rotating machines. The 105 [pF] ceramic coupler(CC) has been developed to continuously measure the PD activity in operating motor stator windings. This paper presents frequency characteristics and laboratory test to compare traditional 80 [pF] epoxy-mica coupler(EMC) and 105 [pF] CC for PD measurement in 6.6 [kV] stator windings.

• Journal of information and communication convergence engineering
• /
• 제6권1호
• /
• pp.55-58
• /
• 2008

In this paper, the new type wiggly directional coupler which uses the fractal coupled shape in coupled sections is presented. A commercial software has been used to analyze this new structure and the simulation results are compared to those of the conventional wiggly directional coupler. To verify the simulation results, the new type wiggly directional coupler was fabricated with the center frequency of 15GHz. The measurement results shows that the coupling of new structure proposed in this paper is more than that of conventional wiggly coupler. The results in this paper also show that the fractal shape coupled lines in wiggling sections can improve the coupling characteristics in wiggly directional coupler.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 G
• /
• pp.3132-3134
• /
• 1999

To realize the power line communication system, the line coupler is one of the most important systems, which must be adjustable to the power line characteristics. In this paper, three kinds of line couplers were designed and simulated with the Pspice, which could be useful to the power line communication systems in C-Band(95kHz-148.5kHz) frequency