• Title, Summary, Keyword: Wideband antenna

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Space-Frequency Block Coded Single Side Band SC-FDMA Transmission System (주파수 공간 블록 부호화된 단일 측대 파형 SC FDMA 전송 시스템)

  • Won, Hui-Chul
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.7
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    • pp.423-429
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    • 2019
  • Recently, a variety of methods for the performance improvement of ultra-high speed wideband wireless transmission systems have been suggested. This paper proposes a space-frequency (SF) block coded single side band (SSB) single carrier (SC)-frequency division multiple access (FDMA) transmission system. In the proposed SSB SC-FDMA system, SF block code is implemented with the complex conjugates, which are formed from discrete Fourier transform (DFT) spreading of pulse amplitude modulation (PAM) signals. As a result, transmit diversity gain can be obtained in the proposed SF block coded SSB SC-FDMA system without any significant increase of the system computational complexity. The simulation result shows that the signal-to-noise power ratio (SNR) performance of the proposed SF block coded SSB SC-FDMA system is approximately 4 dB better than the SNR performance of the conventional SSB SC-FDMA system with single transmit antenna at a symbol error rate (SER) of $10^{-2}$.

Satellite Communication Microstrip 8X2 Away Antenna for TX / RX Dual Operation at Ku-band (Ku 대역 위성통신 송수신 겸용 마이크로스트립 8X2 배열 안테나)

  • 윤재승;전순익;최재익;채종석
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.13 no.6
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    • pp.574-581
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    • 2002
  • Microstrip $8{ imes}2$ sub-array antennas for a extension to active phased array antennas are designed, fabricated and measured for TX/RX dual operation in satellite communication and a reception of satellite broadcasting. For the frequency range from 11.7 to 12.75 GHz for RX and from 14 to 14.5 GHz for TX, two orthogonal linear polarizations of ${pm}45^{\circ}$ are used to transmit and receive simultaneously with one radiator. They adopt dual resonance between two patches for wideband characteristics in RX band and show isolation characteristics over 20 dB. An electrical beam tilt of $30^{\circ}$ is achieved and a tapered power distribution, narrow element spacing are used for the purpose of low side-lobe characteristics.

Design of a Circular Waveguide to Coaxial Cable Transition Employing a Printed Dipole (인쇄형 다이폴을 이용한 Ku-대역 원형도파관-동축선 변환부 설계)

  • Yun, Je-Young;Nho, Joon-Woo;Lee, Chan-Ho;Park, Young-Gyu;Ahn, Bieng-Chearl
    • The Journal of Korean Institute of Information Technology
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    • v.15 no.7
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    • pp.65-71
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    • 2017
  • Circular waveguides are widely used in the realization of reflector-antenna feeds, orthomode transducers, polarizers, filters/multiplexers, and rotary joints. A circular waveguide to coaxial cable transition is often employed to connect a circular waveguide to a transmitter/receiver. This paper presents an in-line circular waveguide to coaxial cable transition employing a printed dipole. The proposed transition consists of a shorted circular waveguide, a microstrip feed line, a microstrip balun, a printed dipole, a parasitic element for wideband operation, and a coaxial probe. Change in the reflection coefficient of the transition versus design parameters is analyzed, from which an optimum design is obtained. Designed transition is fabricated and it reflection coefficient is measured and compared with the simulation. The proposed transition shows reflection coefficient of less than -15dB and higher-order mode levels of less than -20dB at 13.4~17.2GHz.

Spectral Analysis Method for Classification of Liquid Characteristics (액체의 특성 분류를 위한 스펙트럼 분석 방법)

  • Lee, Jonggil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.20 no.12
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    • pp.2206-2212
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    • 2016
  • It is necessary to find characteristic phenomena related with permittivity differences for classification of liquid characteristics. If these phenomena can be remotely detected and characteristics can be extracted, it will be very useful in finding flammable liquid materials and classifying substances of these liquids. Therefore, in this paper, reflection and transmitted signals were analyzed from three receiving antennas with one transmitting antenna using wideband electromagnetic wave signals. Frequency response characteristics of reflected or transmitted signals are different according to characteristics of liquid materials. However, conventional FFT methods cannot be applied due to problems of low resolution caused by data windowing distortion. To minimize these problems, eigenvector analysis method was applied for high resolution spectrum estimation of received signals. From these results, it can be shown that classification of many kinds of liquids are possible using peak frequencies and corresponding peak power values of spectrum estimates obtained from various liquid materials.

Symbol Based Rate Adaptation in Coded MIMO-OFDM Systems (심볼 기반의 적응 변조 기법을 이용한 채널 부호화된 MIMO-OFDM 시스템)

  • Sung, Chang-Kyung;Kim, Ji-Hoon;Lee, In-Kyu
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.1A
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    • pp.50-58
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    • 2008
  • The use of space-division multiple access(SDMA) in the downlink of multiuser multi-input/multi-output(MIMO) wireless transmission systems can provide substantial gains in system throughput. When the channel state information(CSI) is available at the transmitter, a considerable performance improvement can be attained by adapting the transmission rates to the reported CSI. In addition, to combat frequency selective fadings in wideband wireless channels, bit-interleaved coded OFDM(BIC-OFDM) modulation schemes are employed to provide reliable packet delivery by utilizing frequency diversity through channel coding. In this paper, we propose an adaptive modulation and coding(AMC) scheme combined with an opportunistic scheduling technique for the MIMO BIC-OFDM with bandwidth-limited feedback channels. The proposed scheme enhances the link performance by exploiting both the frequency diversity and the multiuser diversity. To reduce the feedback information, the proposed AMC scheme employs rate adaptation methods based on an OFDM symbol rather than on the whole subchannels. Simulation results show that the proposed scheme exhibits a substantial performance gain with a reasonable complexity over single antenna systems.

An Analysis of Satellite Communications System structure for NCW (NCW대비 군 위성통신 구조 분석)

  • Park, Woo-Chul;Cha, Jae-Ryong;Kim, Jae-Hyun
    • Journal of Satellite, Information and Communications
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    • v.4 no.1
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    • pp.1-7
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    • 2009
  • As the information age comes out, the aspect of future war brings about the many changes in terms of war-fighting environment. Accordingly, information superiority and intelligence-centric warfare have been important and new war-fighting concept such as NCW(network centric warfare) have been turned up. This paper proposed all-weather core-strategy communications systems guaranteeing not only the real-time transmission of the information collected in a battlefield and expansion, automation, and rapidity of a battlefield but also broadband, mobility, survivability, and flexibility. The proposed military satellite communications system is classified into wideband mass capacity link, survivability, and the system supporting OTM(on the move) communication for the real-time transmission of battlefield information. This paper analyzed the essential operation concepts and core schemes of the U.S. Army's next generation system, TSAT(Transformational Satellite Communication System). Base on the analysis results, this paper proposed that the architecture of next generation military satellite communications systems for NCW have to provide the data rate, anti-jamming capability, network control and management capability which are optimally adaptable for the wireless channel environments such as jamming and interference and to support the variety of platforms like high-speed mobile vehicles, micromini devices, super-high speed unmanned aerial vehicles. Finally, this paper also proposed that next generation military satellite communications systems need the technologies such as the adaptable multi-antenna, laser link, and next-generation anti-jamming waveform.

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Performance and Jitter Effects Analysis of Single Bit Electro-Optical Sigma-Delta Modulators (단일 비트 전자-광학 시그마-델타 변조기의 성능 및 지터 효과 분석)

  • Nam, Chang-Ho;Ra, Sung-Woong
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.23 no.6
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    • pp.706-715
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    • 2012
  • Electro-optical sigma-delta modulators are the core module of digital receiver to digitize wideband radio-frequency signals directly at an antenna. Electro-optical sigma-delta modulators use a pulsed laser to oversample an input radio-frequency signals at two Mach-Zehnder Interferometer(MZI) and shape the quantization noise using a fiber-lattice accumulator. Decimation filtering is applied to the quantizer output to construct the input signal with high resolution. The jitter affects greatly on reconstructing the original input signal of modulator. This paper analyzes the performance of first order single bit electro-optical sigma-delta modulator in the time domain and the frequency domain. The performance of modulator is analyzed by using asynchronous spectral averaging of the reconstructed signal's spectrum in the frequency domain. The reference value of time jitter is presented by analyzing the performance of jitter effects. This kind of jitter value can be used as a reference value on the design of modulators.

A RF Microstrip Balun Using a Wilkinson Divider and 3-dB Quadrature Couplers (월킨슨 분배기와 90도 위상차 분배기를 이용한 RF 마이크로스트립 발룬)

  • Park Ung-Hee;Lim Jong-Sik;Kim Joung-Myoun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.16 no.3
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    • pp.246-252
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    • 2005
  • A RF microstrip balun having low transmission loss for the balanced receiving dipole antenna is designed and fabricated using a three-section Wilkinson divider and two 3-dB quadrature couplers. It considers two types of the three-section Wilkinson dividers, the Cohn's optimum three-section structure and the miniaturized three-section structure, for wideband power splitting. Also, two 3-dB quadrature couplers for 180 degrees of phase difference adopt a twist-wire coaxial cable. The fabricated first balun having the Cohn's optimum three-section Wilkinson divider has 0.5 dB of transmission loss, $\pm$0.2 dB of amplitude imbalance, and 180$\pm$2.3 degrees of phase imbalance over 400 to 1000 MHz by measurement. The second one using the miniaturized three-section Wilkinson divider shows 1.0 dB of transmission loss, $\pm$0.7 dB of amplitude imbalance, and 180$\pm$8.8 degrees of phase imbalance over the same frequency band.

Program Development for Wideband Channel Sounding and Analysis (광대역 채널 측정 및 분석을 위한 프로그램 개발)

  • Ko Geo Da;Park Noh Joon;Kang Young Jin;Song Moon Kyou
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.2
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    • pp.380-385
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    • 2006
  • In this paper, a program that can be utilized to measure and analyze radio propagation characteristics is developed. This program is able to control the measurement instruments including spectrum analyzer through GPIB interface and analyze the measured data to yield mean excess delay and RMS delay spread. The measured path loss can be compared with theoretical value in free space or inside a tunnel. The measured and analyzed results can also be presented in the forms of graphs. As these tasks can be conducted on the spot of the measurements, this program is very helpful in performing and verifying the measurements immediately. In this thesis radio propagation characteristics with frequency bands of 2.45 and 5.8GHz in subway tunnels are measured by using the program. Path loss and delay spread in subway tunnel is measured and compared according to the form of antenna beam and LOS(Line of Sight) and N-LOS(Non-Line of Sight).

A 30 GHz Band Low Noise for Satellite Communications Payload using MMIC Circuits (MMIC 회로를 이용한 위성중계기용 30GHz대 저잡음증폭기 모듈 개발)

  • 염인복;김정환
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.11 no.5
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    • pp.796-805
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    • 2000
  • A 30GHz band low noise amplifier module, which has linear gain of 30dB and noise figure of 2.6dB, for 30GHz satellite communication transponder was developed by use of MMIC and thin film MIC technologies. Two kinds of MMIC circuits were used for the low noise amplifier module, the first one is ultra low noise MMIC circuit and the other is wideband and high gain MMIC circuit. The pHEMT technology with 0.15$mu extrm{m}$ of gate length was applied for MMIC fabrication. Thin film microstrip lines on alumina substrate were used to interconnect two MMIC chips, and the thick film bias circuit board were developed to provide the stabilized DC bias. The input interface of the low noise amplifier module was designed with waveguide type to receive the signal from antenna directly, and the output port was adopted with K-type coaxial connector for interface with the frequency converter module behind the low noise amplifier module. Space qualified manufacturing processes were applied to manufacture and assemble the low noise amplifier module, and space qualification level of environment tests including thermal and vibration test were performed for it. The developed low noise amplifier was measured to show 30dB of minimum gain, $\pm$0.3dB of gain flatness, and 2.6dB of maximum noise figure over the desired operating frequency range from 30 to 31 GHz.

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