• Title/Summary/Keyword: Variable Reflector

Search Result 15, Processing Time 0.032 seconds

A Reconfigurable Directional Coupler Using a Variable Impedance Mismatch Reflector for High Isolation

  • Lee, Han Lim;Park, Dong-Hoon;Lee, Moon-Que
    • Journal of electromagnetic engineering and science
    • /
    • v.16 no.4
    • /
    • 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.

DEVELOPMENT OF AN AUTOMATIZED DIFFERENTIAL PHOTOMETRY SYSTEM FOR THE 61CM REFLECTOR OF SOBAEKSAN OBSERVATORY (소백산 천문대 61CM 반사망원경을 위한 자동 차등측광 시스템의 개발)

  • Park, Nam-Gyu
    • Publications of The Korean Astronomical Society
    • /
    • v.8 no.1
    • /
    • pp.185-197
    • /
    • 1993
  • We developed an Automatized Differential Photometry System (ADPS) to achieve high time resolution and high efficiency in the photometric observations of short period variable stars. This ADPS has been introduced to the CCD camera system attached to the 6lcm Reflector at Sobaeksan Astronomy Observatory. Several new algorithms were devised for the controlling the telescope. the star recognition in a CCD frame and the aperture photometry, etc..As the result, the differential photometric observation was fully automatized without any manual control, and much faster data acquisition could be achieved over the conventional photoelectric differential photometry.

  • PDF

Micro structural characteristics of Bragg reflector of SMR type FBAR device deposited by RF magnetron sputtering (RF 마그네트론 스퍼터링에 의해 증착된 SMR 구조 FBAR 소자의 Bragg 반사층의 미세구조 특성에 관한 연구)

  • Park, Sung-Hyun;Lee, Sun-Beom;Lee, Neung-Heon;Shin, Young-Hwa
    • Proceedings of the KIEE Conference
    • /
    • 2005.07c
    • /
    • pp.1992-1994
    • /
    • 2005
  • In this study, Bragg reflector was formed as tungsten(W) and $SiO_2$ deposited by RF magnetron sputtering according to variable conditions of RF power and working pressure to apply to the SMR type FBAR device, one of the next generation mobile communication devices. The micro-structural properties such as a crystal orientation, roughness and micro- structure were measured by XRD, AFM and SEM and the best condition of Bragg reflector was elicited with analyzing that results of the thin films about each conditions. Finally, FBAR device was fabricated with applying the Bragg reflector was formed on the best condition and measured the resonance properties and compared other research and considered it.

  • PDF

Structure characteristics of $SiO_2$ thin film of the FBAR Bragg reflector (FBAR 소자의 Bragg 반사층의 $SiO_2$ 박막 특성에 관한 연구)

  • Lee, Soon-Bum;Park, Sung-Hyun;Lee, Neung-Heon;Shin, Young-Hwa
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • 2005.07a
    • /
    • pp.377-378
    • /
    • 2005
  • In this study, $SiO_2$ thin film was deposited on variable conditions of the RF power and working pressure by RF magnetron sputtering to apply to the Bragg reflector of the SMR type FBAR device. A crystal orientation and microstructure of $SiO_2$ thin film was studied by using the XRD, AFM and SEM. The best condition was obtained through analyzing the structural characteristics of thin film. Finally, FBAR device was fabricated with applying the best condition of $SiO_2$ thin film and the resonant characteristics was investigated by network analyzer to verify application possibility as a efficient device.

  • PDF

Surface Emitting Terahertz Transistor Based on Charge Plasma Oscillation

  • Kumar, Mirgender;Park, Si-Hyun
    • Current Optics and Photonics
    • /
    • v.1 no.5
    • /
    • pp.544-550
    • /
    • 2017
  • This simulation based study reports a novel tunable, compact, room temperature terahertz (THz) transistor source, operated on the concept of charge plasma oscillation with the capability of radiating within a terahertz gap. A vertical cavity with a quasi-periodic distributed-Bragg-reflector has been attached to a THz plasma wave transistor to achieve a monochromatic coherent surface emission for single as well as multi-color operation. The resonance frequency has been tuned from 0.5 to 1.5 THz with the variable quality factor of the optical cavity from 5 to 290 and slope efficiency maximized to 11. The proposed surface emitting terahertz transistor is able to satisfy the demand for compact solid state terahertz sources in the field of teratronics. The proposed device can be integrated with Si CMOS technology and has opened the way towards the development of silicon photonics.

A Study on Focus Position Control of Reflector Using Fuzzy Controller (퍼지제어기를 이용한 반사경의 초점 위치제어에 관한 연구)

  • Jeong, Hoi-Seong;Kim, Jun-Su;Kim, Hye-Ran;Kim, Gwan-Hyung;Lee, Hyung-Ki
    • Journal of the Korean Institute of Intelligent Systems
    • /
    • v.21 no.5
    • /
    • pp.645-652
    • /
    • 2011
  • The present study investigated the tracking system of a reflector to trace the movement of sun. The system was designed to minimize the error between the vertical vector of reflector and the position of sun. The proposed system was able to collect the sun lights at a point as a useful source of light energy and transmit the collected light to a remote area through optical fibers. Also the study successfully solved the controller design problem due to the complexity of modeling of the sun tracking system using a fuzzy logic controller which mimics human reasoning.

A Study of the Fabrication and Enhancement of Film Bulk Acoustic Wave Resonator using Two-Step Deposition Method of Piezoelectric Layer (압전층의 2단 증착법을 이용한 체적 음향파 박막형 공진기의 제작과 성능향상에 관한 연구)

  • Park Sung-Hyun;Chu Soon-Nam;Lee Neung-Heon
    • The Transactions of the Korean Institute of Electrical Engineers C
    • /
    • v.54 no.7
    • /
    • pp.308-314
    • /
    • 2005
  • The 2 GHz film bulk acoustic wave resonator(FBAR), one of the most necessary device of the next generation mobile communication system, consisted of solidly mounted resonator(SMR) structure using Brags reflector, was researched in this paper The FBAR applied SiO$_{2}$ and W had large difference of the acoustic impedance to reflector Al to electrode and ZnO to piezoelectric layer. Specially, the FBAR applied the two-step deposition method to improve the c-axis orientation and increase reproducibility of the fabrication device had good performance. The electrical properties of plasma such as impedance, resistance, reactance, $V_{pp},\;I{pp}$, VSWR and phase difference of voltage and current, was analyzed and measured by RF sensor with the variable experiment process factors such as gas ratio, RF power and base vacuum level about concerning the thickness, c-axis orientation, adhesion and roughness. The FBAR device about the optimum condition resulted reflection loss(S$_{11}$) of -17 dB, resonance frequency of 1.93 GHz, electric-mechanical coefficient(k$_{eff}$) of 2.38 $\%$ and Qualify factor of 580. It was seen better qualify than the common dielectric filter at present and expected on business to the filter device of 2 GHz bandwidth with the MMIC technology.

Modified Fold Type Helicone Reflector for Efficient Satellite TT&C Having Variable Coverage Area (가변 커버리지를 갖는 위성 관제용 접이식 헬리콘 반사체 안테나 성능 연구)

  • Lee, Sang-Min;Lee, Woo-Kyung
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.20 no.9
    • /
    • pp.914-923
    • /
    • 2009
  • Helix antennas have been widely applied to satellite TT&C, data communication and GPS receiver systems onboard military, remote sensing and communication purpose satellites. The helix antennas are known to be convenient to control impedance and radiation coverage characteristics with a maximum directivity in satellite z-axis. Waveguide horn is commonly used for radar system that needs ultra-wideband pulse for exploration ground radar and electromagnetic disability measurement etc. It has high efficiency and low reflection characteristics provided by the low-profile shape and suppressed radiation distortion. In this paper, a waveguide horn structure incorporated with helix antenna design is proposed for satellite applications that require ultra-wideband pulse radar and high rate RF data communication link to ground station over wide coverage area. The main design concern is to synthesize variable beam forming pattern based on modified horn-helix combination helicone structure such that multi-mission antenna is implemented applicable for TT&C, earth observation, high data rate transmission. Waveguide horn helps to reduce the overall antenna structure size by introduction fold type reflector connected to the tapered helix antenna. The next generation KOMPSAT satellite currently under development requires high-performance precision attitude control system. We present an initial design of a hybrid hern-helix antenna structure suitable for efficient RF communication module design of multi-purpose satellite systems.

A Photometric Study of the W UMa-type Contact Binary GX Aurigae

  • Park, Jang-Ho;Kim, Chun-Hwey;Lee, Jae-Woo
    • Bulletin of the Korean Space Science Society
    • /
    • 2008.10a
    • /
    • pp.29.2-29.2
    • /
    • 2008
  • The CCD photometric observations of the W UMa type contact binary GX Aur were performed for 33 nights from 2004 to 2008 using a 2K CCD camera and Johnson BVRI filter system attached to the 61cm reflector at Sobaeksan Optical Astronomy Observatory (SOAO). From our observations, the first BVRI light curves of GX Aur were completed and eight new times of minima (primary: 4, secondary: 4) were obtained. All the times of minima including our timings were collected and analyzed to see the dynamical behavior of GX Aur system. Intensive analysis of our BVRI lightcurves with the recent Wilson-Devinney binary model shows that GX Aur is an over-contact binary whose component stars have equal mass and time-variable spots.

  • PDF

Ultra Precision cutting Characteristics for Al 6061 (Al 6061의 초정밀 절삭특성)

  • 박상진
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
    • /
    • 2000.04a
    • /
    • pp.591-596
    • /
    • 2000
  • The needs of ultra precision machined parts is increase every days. But the experimental data of nonferrous metal is insufficient. The cutting behavior in micro cutting area is different from that of traditional cutting because of the size effect. Al6061 is widely used as optical parts such as LASER reflector's mirror or multimedia instrument. Al6061 opper is machined by ultra precision machine with natural diamond tool. From the experiment and discussion on the cutting force and worked surface roughness as the variable spindle speed, feed rate and depth of cut. As a result, the cutting force increases as the increasing depth of cut, but the worked surface roughness does not increase so much. The surface roughness is good when spindle sped is above 1200rpm, and feed rate is small. The influence of depth of cut is very small.

  • PDF