• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.131-136
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• 2015

In this paper, prior to the flight model X-band dual-mode circular cavity filter required for the high power transmission of the observation payload in the geostationary satellite, the development model are designed and analyzed to show the analytical multipactor requirement margin. First of all, the multipaction breakdown power sensitivities were analyzed by changing the iris width and thickness within the filter, and through that the iris width and thickness was selected and then the multipaction threshold powers over the frequencies within the bandwidth were analyzed and the required margin of 8 dB was obtained. Also for the high power transmission filter, another important phenomena known as corona breakdown are analyzed for the iris width and thickness changes. Finally the development model manufactured was tested and the results met the key requirements.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2412-2418
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• 2009

As an astonishing progress of FTTH infrastructure, the new technologies have been widely studied to use the tantalizing benefits of high bandwidth in fiber optic cable. In this paper, a new VONU is presented to perform all necessary optical functions. It can converts digital and analog CATV signals and satellite-based signal transmitted via one fiber optic cable to electrical signals (electric lights). However, most previous VONU systems have the problems such as interference between difference services, signal distortion, and noise increasing rate. These problems cause the quality deterioration in broadcasting. Therefore, we suggest the new VONU system to solve all problems listed above. In addition, we show that how our system performs well by measuring the real data with implemented system.

• Journal of The Korean Astronomical Society
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• v.46 no.6
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• pp.225-234
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• 2013

We develop a radio receiver system operating at ${\lambda}{\sim}1.3$ mm for the 6 m telescope of Seoul Radio Astronomy Observatory. It consists of a dual polarization receiver, a couple of IF processing units, two FFT spectrometers, and associated software. By adopting sideband-separating superconductor mixers with image band terminated to waveguide load at 4.2 K, we achieve $T_{RX}{\leq}100$ K and $T_{sys}$ less than 150 K at best weather condition over 210-250 GHz frequency range. The intermediate frequency signal of 3.5-4.5 GHz is down converted to 0-1 GHz and fed into the FFT spectrometers. The spectrometer covers 1 GHz bandwidth with a spectral resolution of 61 KHz. Test observations are conducted toward several radio sources to evaluate the performance of the system. Aperture and beam efficiencies measured by observing planets are found to be typically 44 ~ 59% and 47 ~ 61%, respectively over the RF band, which are consistent with those measured at 3 mm band previously.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.11
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• pp.937-950
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• 2015

Microstrip reflectarray is an antenna which controls its radiation pattern with a number of reflective elements. Conventionally, the reflectarray has been researched to replace curved reflector antennas. In this paper, design theories of reflectarray is briefly introduced, and research trends of high gain and broadband reflectarrays are reviewed. To improve the gain of the reflectarrays, it is required that the reflection phase errors on the reflectarray surface be minimized. For this purpose, sufficiently wide reflection phase range and low phase sensitivity should be realized with the designed element. For bandwidth improvement, the reflection phase of the element should be linear with the frequency variation. In this paper, various researches to improve the reflection phase characteristics of the element for high gain and broadband reflectarrays, such as multi-layer and single-layer multi-resonant structures, are reviewed. Also, dual-reflectarray configuration for compact antenna design is reviewed. Finally, various applications of reflectarrays such as contoured beam, near-field focusing, and RCS reduction are reviewed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.11
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• pp.1194-1200
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• 2009

An internal antenna which has 1 cc volume was implemented on the FPCB(Flexible Printed Circuit Board) for the mobile phone. We increased antenna gain and efficiency by the applying of current direction concept on the antenna pattern for this small antenna. Short antenna length for the GSM band was compensated by the spiral inductor on the FPCB. For broadening bandwidth on GSM band, it's applied 2 spiral inductors. A conductor pattern for the DCS band was positioned perpendicular with the FPCB. Antenna was implemented on FPCB that is dielectric constant 4.4 and thickness 0.05 mm, and FPCB was attached on a carrier dimensioned $L{\times}W{\times}H=30{\times}7{\times}5\;mm$. Measurements showed that max. VSWR 2:1, efficiency 42.49~60.95 % and 47.95~73.21 %, average gain -3.72~-2.15 dBi and -3.19~-1.35 dBi on the GSM and DCS band, respectively. These results are good performances among the small antenna. And the radiation patterns are omnidirectional on the H-plane to both band.

• The Journal of the Acoustical Society of Korea
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• v.24 no.1
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• pp.52-57
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• 2005

The adaptive multirate wideband (AMR-WB) speech coder has an extended audio bandwidth from 50 Hz to 7 kBz and operates on nine speech coding bit-rates from 6.6 to 23.85 kbit/s. In this Paper, we present the real-time implementation of AMR-WB speech coder using 16bit fixed-point TMS320C5509 that has dual MAC units. Firstly, We implemented AMR-WB speech coder in C 1anguage level using intrinsics, and then performed optimization in assembly language. The computational complexity of the implemented AMR-WB coder at 23.85 kbit/s is 42.9 Mclocks. And this coder needs the program memory of 15.1 kwords, data ROM of 9.2 kwords and data RAM of 13.9 kwords.

• ETRI Journal
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• v.38 no.5
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• pp.981-987
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• 2016

We present a cost-effective dual polarization quadrature phase-shift coherent receiver module using a silica planar lightwave circuit (PLC) hybrid assembly. Two polarization beam splitters and two $90^{\circ}$ optical hybrids are monolithically integrated in one silica PLC chip with an index contrast of $2%-{\Delta}$. Two four-channel spot-size converter integrated waveguide-photodetector (PD) arrays are bonded on PD carriers for transverse-electric/transverse-magnetic polarization, and butt-coupled to a polished facet of the PLC using a simple chip-to-chip bonding method. Instead of a ceramic sub-mount, a low-cost printed circuit board is applied in the module. A stepped CuW block is used to dissipate the heat generated from trans-impedance amplifiers and to vertically align RF transmission lines. The fabricated coherent receiver shows a 3-dB bandwidth of 26 GHz and a common mode rejection ratio of 16 dB at 22 GHz for a local oscillator optical input. A bit error rate of $8.3{\times}10^{-11}$ is achieved at a 112-Gbps back-to-back transmission with off-line digital signal processing.

• Journal of IKEEE
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• v.7 no.2 s.13
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• pp.223-229
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• 2003

In this thesis, the characteristics of an inverted-F antenna for the 2.4GHz and 5.8GHz zwirless local area network(WLAN) have been analysed in terms of the variation of design parameters. The antenna can be integrated on WLAN for notebook printed circuit board, and the characteristics in terms of the variation of the gap between feed line and shorting stub, gap between antenna's leg and ground plane, antenna leg's width, substrate's height and dielectric constant are analysed. By using these characterization plot of design parameter, the tuning techniques are proposed to design optimum antenna. The designed antenna has 170MHz, 500MHz frequency bandwidth ,VSWR is 1.6, 1.14 and 3.5dBi gain.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.12
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• pp.1337-1342
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• 2012

In this paper, we propose a novel reconfigurable antenna that can change the electrical shape of the matching network using RF switches of PIN diodes. The designed antenna operates at two different modes that are Mode 1 (HSDPA band, 2.1~2.2 GHz) and Mode 2(WiBro WiFi band, 2.3~2.5 GHz). The antenna is built on both sides of a polyarcylate substrate. The measured reflection coefficient shows a matching bandwidth of 547 MHz($S_{11}$ <-3 dB, 2.035~2.582 GHz) for Mode 1 and 600 MHz($S_{11}$ <-3 dB, 2.2~2.8 GHz) for Mode 2, and it shows average vertical gains of -4.4 dBi and -4.5 dBi in x-y plane, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.6
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• pp.628-636
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• 2014

This paper describes the design and analysis of five-element planar array antenna of an anti-jamming satellite navigation system. We propose a design of multi-layer patch antenna for Global Positioning System(GPS) $L_1/L_2$ dual bands. The proposed antenna has two ports feeding network with a hybrid chip coupler for a broad bandwidth with Right-Handed Circular Polarization(RHCP). The measurement results show the bore-sight gains of 1.10 dBic($L_1$) and 0.37 dBic($L_2$) for the center element. The bore-sight gains of an edge element are 0.99 dBic($L_1$) and -0.57 dBic($L_2$). At a fixed elevation angle of $30^{\circ}$, antennas show average gains of -2.08 dBic ($L_1$) and -5.33 dBic($L_2$) for the center element, and average gains of -0.40 dBic($L_1$) and -2.09 dBic($L_2$) for the edge elements. The results demonstrate that the proposed array antenna is suitable for anti-jamming applications.