• Journal of Sensor Science and Technology
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• v.6 no.6
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• pp.466-475
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• 1997

In this paper, an implantable middle ear hearing aids using an electromagnetic transducer which consists of a tiny coil and a magnet is designed, and objective design method to implement a vibrator of the electromagnetic type transducer is proposed. Sound characteristic of the electromagnetic type vibrator is excellent but power transfer rate is lower than that of a ceramic type. To improve power transfer efficiency of system, external and inner part of a middle ear system is designed using FM transmission method. We implemented an experimental set of the designed transducer, inner part, and outer part. Then, we measured vibration characteristics of a metal strip and a temporal bone of a dead body. As the results, we confirmed the advantage of FM method and showed that designed transducer could effectively transmit vibration of amplified input sound pressure to ossicle.

• Journal of the Korea Society for Simulation
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• v.20 no.1
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• pp.107-116
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• 2011

Recently, femtocell has been concerned as one of effective solutions to relieve shadow region and provide high quality services to users in indoor environments. Even though femtocell offers various benefits to cellular operators and users, many technical issues, such as interference coordination, network synchronization, self-configuration, self-optimization, and so on, should be solved to deploy the femtocell in current network. In this paper, we develop a simulator for evaluating performance of long term evolution (LTE) femtocell systems under various interference scenarios. The simulator consists of a main-module and five sub-modules. The main-module connects and manages five sub-modules which have the functionality managing user mobility, packet scheduling, call admission control, traffic generation, and modulation and coding scheme (MCS). To provide user convenience, the simulator adopts graphical user interface (GUI) which can observes simulation results in real time. We expect that this simulator can contribute to developing effective femtocell systems by supporting a tool for analyzing the effect of interference between macrocell and femtocell.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3A
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• pp.171-178
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• 2003

In this paper, We has proposed two DGS(Defected Ground Structure) resonators and designed the low-pass filter using the proposed DGS types. This structure consists of two rectangular slots, a ‘II type’ slot on the ground plane, and the stub at the transmission line. It has strong advantages that can vary the return loss at the passband freely and also can easily tune the attenuation pole frequency at the stopband. For enhancing the poor skirt property at the cutoff frequency of the Single Stub ‘II Type’ DGS cell, we have obtained the steep slope attenuation characteristic by combining the rectangular slot on both sides of the DGS. This type of the LPF with the proposed structure can be made more smaller than the existing filters and be used to find the various applications for eliminating the hamonics and spurious mode at WLL and the 2.4 GHz ISM band systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.7
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• pp.844-847
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• 2012

By using LHTL(Left-Handed Transmission Line) which is a form of a metamaterial and conventional RHTL (Right-Handed Transmission Line), we designed, fabricated and tested a broadband $90^{\circ}$ coupler which is a basic circuit for I-Q vector signal generation. Synthetic LHTL and RHTL were implemented with capacitors and inductors only, that the size is minimized. Also, by implementing a Wilkinson power divider which is required for the suggested circuit using a synthetic RHTL, the size of whole circuit is only $11mm{\times}12mm$. For the frequency range 0.8~1.25 GHz, the phase difference at the outputs maintained $90^{\circ}{\pm}5^{\circ}$ and thus, a broadband $90^{\circ}$ coupler could be made in a compact form. for the same frequency range, the insertion loss is less than 1.6 dB and return loss is more than 10.1 dB. To the best of our knowledge, this is the smallest and broadband $90^{\circ}$ coupler for the frequency range and if the circuit is made with MMIC(Monolithic Microwave Integrated Circuit) technology, the size will be reduced much further.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.1
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• pp.41-49
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• 2007

RFID in which subminiature IC chip with the indentified information is built a core technique that can recognize, trace and manage various information of an object using radio frequency in the age of Ubiquitous. Several pressing matters about an infringement of Privacy and a security of private information should be settled as soon as possible because an information of specific circumstance can be collected and used without any awareness by others as well as a private information. In addition, various algorithms with high level of security, which is normally used in wire, can be hardly applied to RFID tag because of a lot of restrictions of tag. In this report, designed-RFID tag based on the standard of ISO/IEC 18000-6 and the problems which originated from the technical procedure of that design were analyzed, and the algorithm which could be applied to the designed-tag was also investigated.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10a
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• pp.238-243
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• 2006

휴대용 단말기의 보급과 인터넷 및 무선 네트워크의 발달로 사용자들이 사용하는 개별 장치들이 보편화되어 있으며, 이들을 서로 유기적으로 엮은 서비스가 등장하고 있다. 본 논문에서는 이러한 서비스의 한 종류로 U-Kiosk의 개념을 소개한다. U-Kiosk는 Kiosk 단말장치나 공용 PC를 사용자 개인의 PC처럼 사용할 수 있도록 하여 이들의 리소스를 직접 제어할 수 있는 기능을 제공한다. 이것을 실현하기 위한 방안으로 본 논문에서는 공용 PC에서 개인 PC의 바탕화면 설정을 포함해 모든 자원을 직접 사용할 수 있도록 하는 부분을 구현하고 설명을 하였으며, 인증 과정에서 사용자의 개입을 최소한으로 줄이는 방법에 대해서 소개한다. 이를 위하여 초소형 보안 단말기인 PANDA를 사용하였으며, Zigbee 통신을 사용하여 사용자의 위치정보를 파악하여 자동으로 인증을 하도록 하는 Transient Authentication의 개념을 도입하였다. 두 컴퓨터 간의 원격 접속을 위해서는 VNC를 이용하여 구현하였으며, 사용자가 공용 PC로부터 일정 거리 안에 있을 경우, 자동으로 원격 접속이 이루어지고, 공용 PC로부터 멀어질 경우 자동으로 접속이 종료되도록 구현하였다. 이를 기반으로 제안하는 U-Kiosk의 개념에 맞는 테스트 베드를 구축 하였다. 이는 UFC Project$^{2)}$의 일부로서 차후 완벽한 인증 인프라를 구축하여 보다 안정적이고 사용하기 편리한 U-Kiosk의 구현에 초석이 될 것이다.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.3
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• pp.20-28
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• 2007

The easiest way to see the phenomena of compressor surge is to show the static and dynamic operation characteristic on the map. Its operation zone will be restricted by the surge limit and, static and transient process must have some margin for it. Effect of rotor moment of inertia, air/gas volumes and heat transfer are factors to cause the transition from the static line. In case a large volume such as heat exchanger exists in the system it will exert a substantial influence to dynamic characteristics. In the present paper, influence of air volume bled from the compressor exit on transient process is investigated with an example of an auxiliary power unit micro-turbine engine. Turbine mass, pressure ratio, rotation speed, power and moment are calculated based on mass and work conservation. Result from the present study can give guidance to design the control system. A computer program is developed to calculate the dynamic process using the MathCAD commercial software.

• The Journal of the Acoustical Society of Korea
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• v.38 no.1
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• pp.67-72
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• 2019

In this study, we investigate the echo reduction performance of miniaturinzed Helmholtz resonators using smaller than wavelength acoustic metamaterial structures. The Helmholtz resonators are formed using air structures which exhibit large impedance mismatch with the surrounding underwater environment. Using the multi-physics software package, we find that significant reduction in the sonar signature is expected and frequency tailoring is possible by controlling the degree of space coiling and inner volume of the resonators. We find that for the basic Helmholtz resonators, up to 7 dB reduction in echo is expected at 10,000 Hz while when the miniaturized Helmoholtz resonators are used, up to 14 dB reduction in echo is expected at 5,000 Hz. In addition, frequency tailoring is demonstrated by varying the internal volume of the Helmholtz resonators and broadband characteristic is shown using superposition of various degree of space coiled structures. Through this study we investigate the effectiveness of the miniaturized Helmholtz resonators formed using air structures and the echo reduction results show promisses in the application of achieving underwater stealth.

• Journal of Advanced Navigation Technology
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• v.23 no.5
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• pp.430-436
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• 2019

It is needed to develop an antenna with features of subminiature, light weight and multi-band operation for the variaty services in maritime and industrial fields. The PCB pattern antenna is one of the appropreiate antennas solving these requirements. In this research, the design and fabrication of the PCB pattern antenna operating on the single band of 920 MHz are investigated. The final goal is that the development of the dual band PCB pattern antenna operating on 260 MHz and 920 MHz, which is based on the proposed antenna. It is evident that the performance in the frequencies of 902 MHz, 915 MHz and 928 MHz among of 920 MHz ISM band is better than that in other frequencies. It is also confirmed that the differences of the voltage standing wave ratio, return loss, gain and efficiency between three frequencies are less than 5%. It is expected that the development of communication link of 5-10 km is possible when the induced results are applied into the low power wide area (LPWA) network desinged by the rule of -30 dB sensitivity.

• Journal of IKEEE
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• v.25 no.2
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• pp.315-321
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• 2021

In this paper, we have developed the multiple channel measurement system for IC Socket Test. The one can test the current-voltage measurements for pitting the several device specification, which analyze the thin current from several ㎂ to 5A with very low resistor mΩ. The increasement of the IC socket channel with lead pitch under 0.25 mm be need to perform several functions, concurrently. The system to perform these functions be designed to integrate several SMU(source measure unit) on board. So, we can reduce the 2 minutes test time per channel point to 40 sec, with daisy chain test method. Using by graphic interface, I-V curve mode and data logging technologies, we can implement the test flow methods and can make economies the time and cost.