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Effect of the Aperture Ratio on the Impedance Bandwidth of an Aperture Coupled Microstrip Antenna
Kim, Jae-Hyun,Kim, Boo-Gyoun Brno University of Technology 2018 Radioengineering Vol.27 No.1
<P>The effect of the aperture ratio on the impedance bandwidth of an aperture coupled microstrip antenna (ACMA) is investigated according to the coupling strength from a microstrip feed line to a patch. Since the coupling strength between a feed line and a patch of an ACMA with a high permittivity (epsilon(r) = 10) feed substrate is small, the impedance bandwidth of the ACMA increases as the aperture ratio increases beyond 0.1. As the feed substrate thickness increases, the aperture ratio for the maximum impedance bandwidth increases and the ratio of the maximum impedance bandwidth to the impedance bandwidth obtained at the aperture ratio of 0.1 increases. Since the coupling strength between a feed line and a patch of an ACMA with a low permittivity (epsilon(r) = 2.2) feed substrate is large, the maximum impedance bandwidth of the ACMA is approximately the same as the impedance bandwidth obtained at the aperture ratio of 0.1.</P>
Jae-Hyun Kim,Boo-Gyoun Kim 한국전자파학회JEES 2018 Journal of Electromagnetic Engineering and Science Vol.18 No.2
The impedance bandwidth and radiation characteristics of an aperture-coupled microstrip line-fed patch antenna (ACMPA) with a high permittivity (εr = 10) feed substrate suitable for integration with a monolithic microwave integrated circuit (MMIC) are investigated for various feed substrate thicknesses through an experiment and computer simulation. The impedance bandwidth of an ACMPA with a high permittivity feed substrate increases as the feed substrate thickness decreases. Furthermore, the front-to-back ratio of an ACMPA with a high permittivity feed substrate increases and the cross-polarization level decreases as the feed substrate thickness decreases. As the impedance bandwidth of an ACMPA with a high permittivity feed substrate increases and its radiation characteristics improve as the feed substrate thickness decreases, the ACMPA configuration becomes suitable for integration with an MMIC.
Reel-to-reel deposition of YBCO films by spray pyrolysis using nitrate precursors
Kim, Jae-Geun,Hong, Suk-Kwan,Yu, Seok-Koo,Cho, Han-Woo,Kim, Byung-Joo,Ahn, Ji-Hyun,Hong, Gye-Won,Lee, Hee-Gyoun IOP Publishing Ltd 2007 Superconductor science & technology Vol.20 No.10
<P>YBCO films were deposited on a moving substrate by a spray pyrolysis method using nitrate aqueous solution as a precursor. Deposition was done on LaAlO<SUB>3</SUB>(100) single crystal substrate by spraying the precursor mist generated by a concentric nozzle. The cation ratio of the precursor solution was Y:Ba:Cu = 1:2.65:4.5. The distance between the nozzle and the substrate was 15?cm. The substrate was transported with a speed ranging from 0.23 to 0.5?cm?min<SUP>−1</SUP>. Films were deposited at a pressure of 10 and 20?Torr and the substrate temperature varied from 740 to 790 ?C. The oxygen partial pressure was controlled between 1 and 5?Torr. Scanning electron microscope (SEM) and x-ray diffraction (XRD) observations revealed that the films are smooth and highly textured with (00<I>l</I>) planes parallel to the substrate. The highest <I>J</I><SUB>c</SUB> was 1.04?MA?cm<SUP>−2</SUP> at 77?K and self-field for film with a thickness of 0.5??m. </P>
개구면 폭 변화를 이용한 개구면 결합 마이크로스트립 패치 안테나의 대역폭 확장
김재현(Jae-Hyun Kim),구환모(Hwan-Mo Koo),김부균(Boo-Gyoun Kim) 대한전자공학회 2015 전자공학회논문지 Vol.52 No.1
MMIC와 집적이 가능한 큰 유전상수를 가지는 급전 기판을 사용하는 개구면 결합 마이크로스트립 패치 안테나(ACMPA)의 개구면 폭을 변화시켜 ACMPA의 대역폭을 확장하는 방법에 대하여 연구하였다. 개구면의 폭이 증가할수록 ACMPA의 패치공진과 개구면 공진 사이의 상호 공진 영역이 증가하여 대역폭이 증가하였다. 일반적인 개구면의 길이와 폭의 비(10:1)을 가지는 ACMPA의 대역폭 20.8 %를 개구면 폭 변화를 이용하여 최대 35.3 %까지 확장하였다. 개구면 폭 증가에 의한 방사특성 저하는 매우 작았다. The bandwidth enhancement of an aperture coupled microstrip patch antenna(ACMPA) with a high permittivity feed substrate suitable for the integration with MMIC is investigated using variation of an aperture width. As an aperture width increases, the 10 dB return loss bandwidth increases due to the increase of the mutual resonance region between a patch resonance and an aperture resonance. The bandwidth of an ACMPA with extended aperture width is increased up to 35.3 % from 20.8 % of the ACMPA with an aperture of a typical aspect ratio 10:1. The degradation of the radiation characteristics of an ACMPA due to the increase of an aperture width is very small.
선형 배열 안테나의 방사패턴 계산을 위한 Mirror Active Element Pattern 방법
김재현(Jae-Hyun Kim),윤영민(Young-Min Yoon),김부균(Boo-Gyoun Kim) 대한전자공학회 2013 전자공학회논문지 Vol.50 No.8
선형 배열 안테나의 구조가 배열 안테나의 중심을 기준으로 대칭 구조인 점을 이용하여 효율적으로 배열 안테나의 빔 주사각에 따른 방사패턴을 계산할 수 있는 mirror AEP (active element pattern) 방법을 제안한다. Mirror AEP 방법은 AEP 방법과 비교하여 배열 안테나의 방사패턴을 계산하기 위하여 필요한 full-wave 전산모의를 이용하여 구하는 소자의 AEP 수를 약 반으로 줄일 수 있기 때문에 계산 시간을 약 반으로 줄일 수 있다. 배열 안테나를 구성하는 단위 안테나 소자의 방사패턴이 대칭인 경우에는 mirror AEP 방법으로 계산한 방사패턴과 full-wave 전산모의를 이용하여 구한 방사패턴과의 차이가 넓은 빔 주사각 범위에서 매우 작았다. We propose the mirror active element pattern (AEP) method for the radiation pattern computation of linear array antennas versus scan angles. The computation time for the radiation pattern of linear array antennas using the mirror AEP method is reduced by almost half compared to that using the AEP method because the number of AEPs of elements obtained by the full-wave simulation necessary for the radiation pattern computation of linear array antennas is reduced by almost half. The difference between the radiation patterns of linear array antennas obtained by the full-wave simulation and mirror AEP method is very small for wide scan angle range when the radiation pattern of an antenna element is symmetric.
김재현(Jae-Hyun Kim),이지원(Ji-Won Lee),김부균(Boo-Gyoun Kim) 한국전자파학회 2019 한국전자파학회논문지 Vol.30 No.9
주 전송선로의 길이가 λ/2인 기존의 광대역 180° 위상 천이기보다 크기가 작은 주 전송선로의 길이가 λ/4인 새로운 광대역 180° 위상 천이기를 설계하였다. 주 전송선로의 길이가 λ/4인 광대역 180° 위상 천이기와 3 dB 윌킨슨 전력 분배기가 직렬로 연결된 소형 λ/4 광대역 평면 발룬을 PCB에 구현하고 특성을 측정하였다. 입력 포트의 반사손실이 15 dB 이상인 임피던스 대역폭은 52.1 %(7.62~13 GHz)이고, 두 출력 포트의 위상 차이가 175°와 185° 사이인 대역폭은 56.6%(7.09~12.7 GHz)이다. 본 논문에서 구현한 λ/4 광대역 평면 발룬은 기존의 λ/2 광대역 평면 발룬과 특성이 비슷하지만, 길이가 λ/4 짧아져 크기가 11.6 % 이상 작아지는 장점을 가진다. The design of a novel broadband 180° phase shifter, with the main transmission line length of λ/4, which is smaller than a conventional broadband 180° phase shifter with a main transmission line length of λ/2, is proposed in this study. The proposed compact broadband planar balun, consisting of the λ/4 broadband 180° phase shifter and a 3 dB Wilkinson power divider, is implemented on a single-layer PCB and its characteristics are measured. The impedance bandwidth with a return loss of more than 15 dB at the input port is 52.1 %(7.62∼13 GHz), and the bandwidth of the phase differences between the two output ports within the phases 175° and 185° is 56.6 %(7.09∼12.7 GHz). The characteristics of the λ/4 broadband planar balun implemented in this paper are similar to those of the conventional λ/2 broadband planar balun. The length of the λ/4 broadband planar balun is lesser than that of the conventional λ/2 broadband planar balun, thus reducing the overall size by more than 11.6 %.
Deposition of YBCO Thin Film by Aerosol Assisted Spray Pyrolysis Using Nitrates
Byeong-Joo Kim,Seok-Kwan Hong,Jae-Geun Kim,Jung-Ho Kim,Dou, S X,Dunlop, L,Kursumovic, A,MacManus-Driscoll, J L,Hee-Gyoun Lee,Gye-Won Hong IEEE 2011 IEEE transactions on applied superconductivity Vol.21 No.3
<P>Coated conductor by MOCVD shows the best Ic × L performance currently, but cost reduction is still ongoing issue. R&D effort for a process capable of utilizing cheap alternative precursors were tried by many research groups but few of them showed results having potential for replacing current MOCVD. Spray pyrolysis method adopting ultrasonic atomization was tried as one of the possible options. Y123 films have been deposited on LaAlO<SUB>3</SUB> (100) single-crystal and IBAD substrates by aerosol assisted spray pyrolysis method. Ultrasonic atomization was used in order to generate fine droplets of precursor solution made of Y, Ba, Cu nitrate. A pre-heater was located between spraying nozzle and substrate for fast drying and enhancing decomposition of precursors. SEM and XRD observation revealed that deposited films have smooth and dense microstructure. The influence of operating parameters such as cation stoichiometry, oxygen partial pressure, substrate temperature on the microstructure, formation of superconducting 123 phases and superconducting properties of deposited films were tested. Ex-situ conversion was tried to decrease the possible reactions between precursor compounds and buffer layer materials of metal substrate showed the possibility of adopting this technique for epitaxial growth of 123 phase on metal substrate.</P>
Compact DVB-H Antenna With Broad Dual-Band Operation for PMP Applications
Jae-Kyung Wee,Jae Woo Park,In Su Yeom,Boo-Gyoun Kim,Chang Won Jung IEEE 2010 IEEE antennas and wireless propagation letters Vol.9 No.-
<P>A dual-band (UHF: 470-862 MHz; L: 1452-1492 MHz) Digital Video Broadcasting-Handheld (DVB-H) antenna is presented. The proposed antenna is composed of a planar inverted-F antenna (PIFA) with an input impedance matching circuit. The matching circuit improves antenna performance in the broad UHF bands (470-862 MHz: 63%). The proposed antenna has omnidirectional patterns and sufficient gain (average peak gain over 470-862 MHz: 0.9 dBi) for the portable media player (PMP) applications. The antenna is contact with a PMP case (ε<SUB>r</SUB> = 3.2), which is used as a substrate for the size reduction and compact design.</P>