Jae-Jin Koo
Soonchunhyang University
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Jae-Jin Koo.
european microwave conference | 2007
Jae-Jin Koo; Seong-Min Oh; Mun-Su Hwang; Chun-Seon Park; Yongchae Jeong; Jongsik Lim; Kwan-Sun Choi; Dal Ahn
An unequal Wilkinson power divider having rectangular-shaped defected ground structure (DGS) is proposed. DGS microstrip line adopted for the divider is composed of double-layer substrate which removes the ground problem of the previous DGS structures in packaging. The first layer includes DGS on the bottom ground plane. The second substrate of which top metal plane has been removed is attached to the bottom plane of the first layer. At first, a conventional DGS unequal Wilkinson power divider is designed according to the previous method on the first layer, and the second substrate is attached. The proposed DGS with double-layer substrate is described in detail and applied to 1:4 unequal dividers as an application example. The measured unequal Wilkinson power divider has an excellent agreement between prediction and measurement.
international microwave symposium | 2006
Jongsik Lim; Ung-Hee Park; Sungmin Oh; Jae-Jin Koo; Yongchae Jeong; Dal Ahn
A novel ultra-wide band CPW (coplanar waveguide) balun having the structure of multistage Wilkinson power divider is proposed. It has an 180deg phase inverting structure between signal line and ground planes of CPW transmission line. The 3-stage Wilkinson power divider is transformed directly into the ultra-wide band balun without any cost of the size and performances. The measurement shows the right S-parameters as a power divider and the proper out of phase as a balun. The measured amplitude and phase unbalances at output ports are plusmn 0.5dB and plusmn 6deg, respectively over 800~3200MHz, while the maximum insertion loss is 0.8dB
international microwave symposium | 2007
Seong-Min Oh; Jae-Jin Koo; Mun-Su Hwang; Chun-Seon Park; Yongchae Jeong; Jongsik Lim; Kwan-Sun Choi; Dal Ahn
In this paper, an unequal 1:N Wilkinson power divider with variable power dividing ratio is proposed. The proposed unequal power divider is composed of the conventional Wilkinson divider structure, rectangular-shaped defected ground structure (DGS), island in DGS, and varactor diodes of which capacitance is adjustable according to bias voltage. The high impedance value of microstrip line having DGS is going up and down by adjusting the bias voltage for varactor diodes. Output power dividing ratio (N) is adjusted from 2.59 to 10.4 for the unequal power divider with 2 diodes.
IEICE Transactions on Electronics | 2008
Jongsik Lim; Seongmin Oh; Jae-Jin Koo; Yongchae Jeong; Dal Ahn
An unequal Wilkinson power divider with adjustable power dividing ratio is proposed. The proposed power divider consists of rectangular defected ground structure (DGS), isolated island in DGS, and varactor diodes. The impedance of the microstrip line greatly increases due to the DGS, and varies because of the varying capacitance of diodes. The measured unequal dividing ratios vary from 1.97-13.4 and 2.25-10.6 when 2- and 4-diodes are adopted.
The Journal of Korean Institute of Electromagnetic Engineering and Science | 2007
Jong-Sik Lim; Seong-Min Oh; Jae-Jin Koo; Yongchae Jeong; Dal Ahn
In this paper, an unequal 1:N Wilkinson power divider with adjustable dividing ratio is proposed. The proposed unequal power divider is composed of basic Wilkinson structure. It consists of rectangular-shaped defected ground structure (DGS), isolated island pattern in DGS, and varactor diodes of which capacitance depends on bias voltage. The characteristic impedance value of microstrip line having DGS goes up and down by controlling bias voltage for diodes, and consequently the power dividing ratio(N) is adjusted. The obtained N from measurement is which mean the proposed divider has adjustable unequal dividing ratio.
Journal of the Korea Academia-Industrial cooperation Society | 2009
Hyeon-Won Cha; Jae-Jin Koo; Jong-Sik Lim; Dal Ahn
Abstract A design of cascaded distributed amplifier with a broadband amplification is described in this paper. A medium power device with 23dBm,max output power under the optimal narrow-band power matching condition is adopted for the design and fabrication of the cascaded distributed amplifier. In general, conventional distributed amplifiers with the parallel connected input ports have a low gain, and previous cascaded distributed amplifiers show a relatively low output power of 10dBm at most, which is the upper limit of small signal amplification. However, the cascaded distributed amplifier in this paper shows the gain of 18.15±0.75dB and output power of 20dBm over 300MHz~2GHz from the measurement, so it can be well adopted as a wideband driver amplifier. Key Words : Distributed Amplifiers, Wideband Amplifiers * 교신저자 : 임종식([email protected])접수일 09년 05월 26일 수정일 (1차 09년 08월 14일, 2차 09년 08월 18일) 게재확정일 09년 08월 19일 1. 서론 무선으로 이루어지는 각종 이동통신, 방송, 인터넷, 데이터 서비스 시스템에 있어서 정보량의 증가와 고속화에 따라 마이크로파 대역의 무선통신 시스템의 수요가 증가되고 있다. 또한 사용 주파수 대역의 다양화로 인해 광대역에서 동작이 가능한 부품 개발이 요구되고 있다 . 무선 시스템에서 가장 중요한 핵심부품 가운데 하나인 증폭기의 경우에도 이런 광대역화 요구에 부응하기 위하여 광대역 증폭기가 요구되고 있는데, 광대역 증폭기는 다양한 시스템의 주파수 대역에서 필요한 증폭 기능을 제공할 수 있어서 개발된 부품의 사용 효율성을 높일 수 있다 .초고주파 대역에서 광대역 증폭기를 구현하는 방법으로는 출력의 일부를 입력으로 되돌리는 피드백 방법, 특정 주파수 성분을 선택적으로 감쇄시키는 손실정합 방법(lossy matching), 평탄한 이득 특성과 만족할 만한 입력, 출력측 반사계수 특성을 동시에 얻기 위한 평형 증폭기 , 그리고 입·출력 특성이 넓은 주파수에서 특정한 임피던스 값이 되게 하는 분포형 증폭기(distributed amplifier) 등이 있다. 피드백 방법은 안정도 특성이 양호하나, 피드백 되는 전력에 의해 전력 정합과 이득의 평탄도 특성을 동시에 만족하기가 어렵다. 손실정합 방법은 양호한 전압 정재파비 특성을 가지나, 이득이 감소되고 구성하는 능동, 수동 소자의 모델이 높은 정밀도를 가지지 않는다면 평탄한 이득을 기대하기 어렵다. 평형증폭기는 2개의 증폭기를 사용하므로 DC 전력의 소모가 크고, 회로의 크기가
The Journal of Korean Institute of Electromagnetic Engineering and Science | 2008
Mun-Su Hwang; Jae-Jin Koo; Ja-Kyung Koo; Jong-Sik Lim; Dal Ahn; Gyu-Yeol Yang; Jun-Chul Kim; Dongsu Kim; Ung-Hee Park
This paper describes the design of a FEM(Front End Module) having power detection function for mobile handset application. The designed FEM consists of a MMIC(Monolithic Microwave Integrated Circuits) power amplifier chip, SAW Tx filter and duplexer, diode power detector and stripline matching circuit. An LTCC(Low Temperature Co-fired Ceramics) technology is adopted for miniaturized FEM. The frequency band is MHz which is the uplink Tx band of the CDMA mobile system. The size of designed FEM is , which is an ultra-small size even though the power detector circuit is included. All sub-components of FEM have been developed and measured in advance before being integrated into FEM. The measured output power and gain are 27 dBm and 27 dB, respectively. In addition, the measured ACPR characteristics are 46.59 dBc and 55.5 dBc at 885 kHz and 1.98 MHz offset, respectively.
The Journal of Korean Institute of Electromagnetic Engineering and Science | 2007
Jong-Sik Lim; Jae-Jin Koo; Seong-Min Oh; Yongchae Jeong; Dal Ahn
A novel 1:4 unequal wilkinson power divider using rectangular-shaped defected ground structure(DGS) in double layered substrate is proposed for removing the ground problem of DGS in packaging. Rectangular-shared DGS produces the transmission line having much higher characteristic impedance than standard microstrip line. The proposed unequal divider is composed of DGS and double layered substrate in order to be free from the ground problem of DGS patterns in packaging in metal housings. The second substrate is attached to the first substrate which contains DGS pattern on its ground plane at the bottom side to form the double layered substrate. In order to show the validity of the proposed DGS in the double layered substrate, a 1:4 unequal power divider is designed and measured. The predicted and measured performances are shown with an excellent agreement between them.
The Transactions of the Korean Institute of Electrical Engineers | 2007
Jong-Sik Lim; Jae-Jin Koo; Seong-Min Oh; Dal Ahn; Kwansun Choi
Journal of the Korea Academia-Industrial cooperation Society | 2007
Mun-Su Hwang; Jae-Jin Koo; Dal Ahn; Jong-Sik Lim