A Method for Improving Stopband Characteristics of a Dual-Band Filter

Jahyeon Lee,Yeongseog Lim 한국전자파학회JEES 2011 Journal of Electromagnetic Engineering and Science Vol.11 No.3

This paper presents a simple and effective method for improving stopband rejection characteristics of previously studied dual-band filters. Small electric couplings were applied to the symmetrically positioned shunt resonators, which divided each transmission zero into two transmission zeros without any effect on passbands. We were able to achieve improved stopband rejection characteristics by these additional transmission zeros. For the filter application, we designed a dual-band filter with improved stopband characteristics using microstrip quasi-lumped elements. The electric couplings that control the location of transmission zeros are controlled by the distance between symmetric open stubs of the filter. The filter was fabricated with a relative dielectric constant of 3.5 and a thickness of 0.76 ㎜. The fabricated filter has a small size (14.6×13.2×0.76 ㎜) and a low insertion loss when compared with conventional filters.

An Enhanced Skirt Characteristics Triple-Mode Filter

Jahyeon Lee,Hun Nam,Yeongseog Lim 한국전자파학회JEES 2012 Journal of Electromagnetic Engineering and Science Vol.12 No.3

This paper presents a compact microstrip triple-mode filter with enhanced skirt characteristics. The presented triple-mode filter configuration supports three transmission poles and three transmission zeros within the nearby passband. Two of transmission zeros are generated by a triple-mode resonator itself, and the third one is generated by small cross-couplings between the I/O ports. Each resonance condition and the transmission zero generation conditions are analyzed using an equivalent circuit. The bandpass filter is designed for a 2.4 GHz WLAN. The filter was fabricated with a relative dielectic constant of 3.5 and a thickness of 0.76 mm. The fabricated filter has a small size (7.9 mm×7.2 mm, i.e., 0.107 λg×0.098 λg, where λg is guided wavelength at a center frequency) and shows high performing skirt characteristics.

소형의 삼중 모드 공진기와 삼중 모드 필터 설계

이자현(Jahyeon Lee),임영석(Yeongseog Lim) 한국전자파학회 2011 한국전자파학회논문지 Vol.22 No.4

본 논문에서는 새로운 구조의 작은 크기의 삼중 모드 공진기를 제안한다. 제안된 구조는 소형화를 위해 반파장의 Stepped Impedance Resonaotr에 개방 스터브와 단락 스터브를 이용하였으며, 개방 스터브에 의해 자체적으로 하나의 전송 영점을 발생시킨다. 각각의 세 가지 공진 모드에서 발생하는 공진점을 이론적으로 해석하였다. 제안된 삼중 모드 공진기를 이용하여 세 개의 전송 극점과 하나의 전송 영점을 갖는 2.4 ㎓ WLAN에 적용 가능한 대역 통과 필터를 설계 및 제작하였다. 제작된 삼중 모드 필터는 중심 주파수 2.4 ㎓에서 15.8 %의 3 ㏈ 대역폭과 2.4~2.5 ㎓ 통과 대역 내에서 최대 1.17 ㏈ 이하의 삽입 손실을 갖는다. 제작된 삼중 모드 공진기의 필터의 크기는 급전 선로를 포함하여 15.9 ㎜×9.7 ㎜로 기존의 삼중 모드 필터에 대비하여 매우 작은 크기를 갖는다. In this paper, we present a compact triple-mode resonator. The resonator itself can provide three transmission poles and one transmission zero. The resonance condition of each mode is analyzed theoretically, and the transmission zero is generated by open stub. Using this proposed resonator, a compact three pole bandpass filter for 2.4 ㎓ WLAN application with one transmission zero is designed and fabricated. The fabricated triple-mode filter shows 3 ㏈ bandwidth of 15.8 % with the center frequency 2.4 ㎓ and less then 1.17 ㏈ in 2.4~2.5 ㎓ passband. The size of fabricated triple-mode filter including the feed lines is 15.9 ㎜×9.7 ㎜ and very compact compared with previous reported triple-mode filter.

이중 모드 공진기를 이용한 이중 대역 대역 통과 필터 설계

이자현(Jahyeon Lee),임영석(Yeongseog Lim) 한국전자파학회 2011 한국전자파학회논문지 Vol.22 No.2

본 논문에서는 설계 방법이 단순하면서 통과 대역의 대역폭 조절이 독립적으로 가능한 소형의 이중 대역 대역 통과 필터를 제안하였다. 각각의 통과 대역은 서로 다른 두 개의 이중 모드 공진기를 이용하여 독립적으로 설계하였다. 제안된 이중 대역 대역 통과 필터는 세 개의 전송 영점을 갖는다. 두 개의 전송 영점은 각각의 이중 모드 공진기에서 발생하며, 입출력 선로 간의 결합 효과에 의해 추가적으로 하나의 전송 영점이 발생한다. 제안된 이중 대역 대역 통과 필터 설계 방법을 이용하여 2.4/5.7 ㎓ WLAN에 동작하는 이중 대역 대역 통과 필터를 설계 및 제작하였다. A compact microstrip dual-band bandpass filter with controllable bandwidth for each passband is proposed. Each passband is independently designed using two different dual-mode resonators. The proposed dual-band bandpass filter has three transmission zeros. Two transmission zeros are generated by each dual-mode resonator. An additional transmission zero is generated by input/output port coupling. The dual-band bandpass filter application is designed for 2.4/5.7 ㎓ WLAN. Experimental results are presented to validate theory.

2단 분사 PCCI 엔진의 아트킨슨 사이클 적용을 위한 기초 연구

이재현(Jahyeon Lee),김형민(Hyungmin Kim),김기범(Kibum Kim),이기형(Kihyung Lee) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4

It is well known that diesel engines generate a large amount of NOx and PM because of locally excessive richness and overall lean combustion. Recently, a premixed charge compression ignition (PCCI) engine has received attention for its attractive advanced combustion process because this combustion system can reduce NOx and PM simultaneously. However, PCCI engines have a disadvantage that the combustion efficiency is relatively low when the PCCI strategy is applied to conventional diesel engines, the combustion takes place before TDC due to the spontaneous pre-ignition property of diesel. Many researchers have been trying to overcome the drawback by retarding the ignition timing with low compression ratios. In this study a modified cam having the fixed opening timing of the intake valve and the 30° retarded closing timing was employed to reduce the effective compression ratio. Although the Atkinson cycle with a retarded cam leads to a low in-cylinder pressure in the compression stroke, the engine work can increase through the compensation of the max pressure. On that account, we applied various advanced second injection timings to raise the max pressure up to the same pressure as the original cam's.

Polarized Light Emission from Uniaxially Oriented and Polymer-Stabilized AIE Luminogen Thin Films

Koo, Jahyeon,Lim, Seok-In,Lee, Seung Hee,Kim, Jin Soo,Yu, Yeon-Tae,Lee, Cheul-Ro,Kim, Dae-Yoon,Jeong, Kwang-Un American Chemical Society 2019 Macromolecules Vol.52 No.4

<P>Organic materials with linearly polarized luminescence (LPL) properties and good processability are critical to the development of advanced optical devices. To fabricate polymer-stabilized thin films with LPL properties, dicyanodistyrylbenzene-based reactive luminogens (abbreviated as DRL) containing both vinyl and thiol units were newly synthesized. On the basis of morphological observations combined with thermal and scattering analyses, it was found that DRL has a nematic liquid crystal mesophase. DRL molecules were uniaxially oriented by surface alignment layer and stabilized by thiol-ene click reaction. Uniaxially oriented and polymer-stabilized DRL thin films showed excellent chemical resistance as well as mechanical and thermal stability due to the chemically cross-linked polymer network. The DRL polymer film exhibited strong emission at 564 nm with remarkable LPL property. The polymer-stabilized films obtained from reactive luminogens with aggregation-induced enhanced emission (AIEE) properties have great potential for the application of advanced optical devices.</P> [FIG OMISSION]</BR>

제어 가능한 전송 영점을 갖는 CRLH 전송 선로

이자현(Jahyeon Lee),김경근(Kyoungkeun Kim),임영석(Yeongseog Lim) 한국전자파학회 2010 한국전자파학회논문지 Vol.21 No.6

본 논문에서는 제어 가능한 전송 영점을 갖는 새로운 Composite Right/Left Handed(CRLH) 전송 선로가 제안 되었다. 제안된 CRLH 전송 선로의 단위 셀은 MIM 형태의 커패시터와 마이크로스트립 스터브 인덕터와 co-planar waveguide(CPW) 인덕터로 구성되어 있다. 또한 제안된 전송 선로는 각각의 단위 셀의 MIM 커패시터와 마이크로스트립 스터브 인덕터에서 발생하는 전자기 결합 성분에 의해 차단 대역에 두 개의 전송 영점이 발생한다. 제안된 전송 영점을 갖는 CRLH 전송 선로의 응용으로 UWB 시스템을 위한 광대역 통과 필터를 설계 및 제작하였다. 측정 결과, 통과 대역의 하측과 상측에 전송 영점이 발생하는 것을 확인하였으며, 대역 통과 필터의 급전 구조를 제외한 크기는 8 ㎜×8 ㎜으로 λg/4 이하의 전기적 크기를 갖는다. In this paper, a novel CRLH-TL unit cell with controllable transmission zeros was proposed. Proposed composite right/left handed transmission line(CRLH-TL) unit cell is implemented in the form of the metal-insulator-metal(MIM) capacitors, the microstrip stub inductors, and the co-planar waveguide(CPW) inductor. And this proposed CRLH-TL generates two transmission zeros in lower/upper passband by the effort of electromagnetic couplings between each MIM capacitors and microstrip stub inductors. Using this proposed CRLH-TL, broad bandpass filter for UWB system was designed and fabricated. The measured results reveal that the two transmission zeros are observed in lower/upper passband and the overall size of the filter, excluding the feed line is about 8 ㎜×8 ㎜, less then λg/4 on electric size.

다중 대역 필터 설계를 위한 필터 합성법

이혜선(Hyesun Lee),이자현(Jahyeon Lee),임영석(Yeongseog Lim) 한국전자파학회 2010 한국전자파학회논문지 Vol.21 No.11

본 논문에서는 새로운 다중 대역 필터의 LC 프로토 타입 합성 방법을 제안하였다. 주어진 주파수 응답을 갖는 다중 대역 필터를 합성하기 위해, 극점과 영점의 배열 구조를 제안하였고, 최적화 알고리즘을 이용하여 극점과 영점의 최적화된 위치를 찾는 과정을 제안하였다. 또한, 극점과 영점으로 계산된 전달 및 반사 함수를 이용하여 다중 대역 필터의 준 타원 LC 프로토 타입을 합성하는 일련의 과정을 보였다. 제안된 다중 대역 필터의 LC 프로토 타입 합성법을 이용하여 GSM(880~960 ㎒), ISM(2,400~2,500 ㎒) 대역에서 동작하는 이중 대역 필터와 GSM(880~960 ㎒), ISM(2,400~2,500, 5,725~5,850 ㎒) 대역에서 동작하는 삼중 대역 필터를 설계 및 제작하였다. In this paper, we presented a new LC prototype synthesis method for the multi-band filter. For synthesis a multi-band filter with the required frequency response, we proposed the diagram of poles and zeros, also, we proposed the optimization process for finding the combination of optimized poles and zeros. From the transfer and reflection functions calculated from poles and zeros, we performed the quasi-elliptic LC prototype synthesis of multi-band filter. Using the proposed LC prototype synthesis method of multi-band filter, dual-band filter operating at GSM(880~960 ㎒) and ISM(2,400~2,500 ㎒) and triple-band filter operating at GSM(880~960 ㎒) and ISM(2,400~2,500, 5,725~5,850 ㎒) were designed and fabricated.

Sleep-Related Eating Disorder and Nocturnal Eating Syndrome

Cho Jahyeon,Lee Ji Hyun,Hong Seung-Chul 대한수면학회 2020 sleep medicine research Vol.11 No.2

Eating and sleeping are vital functions of human life. They reciprocally influence each other in both quality and quantity. Nocturnal eating syndrome (NES) and sleep-related eating disorder (SRED) are two distinct diseases that share symptomatology of an abnormal association between the timing of eating and sleep. NES is represented by purging, a non-controllable manner of eating in the evening before sleep, followed by morning anorexia. SRED is a chronic condition showing eating episodes after sleep onset with partial to complete amnesia. Terminology was used confusedly until the third edition of the International Classification of Sleep Disorders, which defined SRED in the parasomnia section. Unlike NES, SRED usually does not respond to psychotherapy but to medication, most promisingly, to topiramate. Both are related to weight control problems, leading to obesity or excessive preoccupation with weight control issues.

μ-Raman 분광법을 활용한 생활화학제품 중 미세플라스틱 분석

Nagyeong Kim,Jahyeon Kang,Ingyu Lee,Hyunook Kim 한국분석과학회 2024 학술대회논문집 Vol.2024 No.5