• Title, Summary, Keyword: Wideband antenna

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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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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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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 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.

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.