• Title/Summary/Keyword: Antenna Weight

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Operation Mode Design and Performance Analysis for Small Satellite SAR Payload (초소형위성 SAR 탑재체 운용모드 설계 및 성능분석)

  • Park, Jongmin;Kim, Dongsik;Kim, Wansik;Kim, Jongpil
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.19 no.5
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    • pp.169-173
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    • 2019
  • In this paper, SAR payload operation mode design method, results and performance analysis results are suggested. To SAR payload design, pramary parameter should be identified and designed. It is designed considering the small satellite of less than 100kg operated in low earth orbit. Also, an antenna structure for small size and light weight is proposed. Performance analysis is performed by applying the design values.

A Signal Detection of Minimum Variance Algorithm on Linear Constraints

  • Kwan Hyeong Lee
    • International Journal of Internet, Broadcasting and Communication
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    • v.15 no.3
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    • pp.8-13
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    • 2023
  • We propose a method for removing interference and noise to estimate target information. In wireless channels, information signals are subject to interference and noise, making it is difficult to accurately estimate the desired signal. To estimate the desired information signal, it is essential to remove the noise and interference from the received signal, extracting only the desired signal. If the received signal noise and interference are not removed, the estimated information signal will have a large error in distance and direction, and the exact location of the target cannot be estimated. This study aims to accurately estimate the desired target in space. The objective is to achieve more presice target estimation than existing methods and enhance target resolution.An estimation method is proposed to improve the accuracy of target estimation. The proposed target estimation method obtains optimal weights using linear constraints and the minimum variance method. Through simulation, the performance of the proposed method and the existing method is analyzed. The proposed method successfully estimated all four targets, while the existing method only estimated two targets. The results show that the proposed method has better resolutiopn and superior estimation capability than the existing method.

Design and simulation of a rectangular planar printed circuit board coil for nuclear magnetic resonance, radio frequency energy harvesting, and wireless power transfer devices

  • Mostafa Noohi;Adel Pourmand;Habib Badri Ghavifekr;Ali Mirvakili
    • ETRI Journal
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    • v.46 no.4
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    • pp.581-594
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    • 2024
  • In this study, a planar printed circuit board (PCB) coil with FR4 substrate was designed and simulated using the finite element method, and the results were analyzed in the frequency domain. This coil can be used in wireless power transfer (WPT) as a transmitter or receiver, eliminating wires. It can also be used as the receiver in radio frequency energy-harvesting (RF-EH) systems by optimizing the planar PCB coil to convert radio-wave energy into electricity, and it can be employed as an excitation (transmitter) or receiver coil in nuclear magnetic resonance (NMR) spectroscopy. This PCB coil can replace the conventional coil, yielding a reduced occupied volume, a fine-tuned design, reduced weight, and increased efficiency. Based on the calculated gain, power, and electromagnetic and electric field results, this planar PCB coil can be implemented in WPT, NMR spectroscopy, and RF-EH devices with minor changes. In applications such as NMR spectroscopy, it can be used as a transceiver planar PCB coil. In this design, at frequencies of 915 MHz and 40 MHz with 5 mm between coils, we received powers of 287.3 μW and 480 μW, respectively, which are suitable for an NMR coil or RF-EH system.

Performance Improvement of Downlink Real-Time Traffic Transmission Using MIMO-OFDMA Systems Based on Beamforming (Beamforming 기반 MIMO-OFDMA 시스템을 이용한 하향링크 실시간 트래픽 전송 성능 개선)

  • Yang Suck-Chel;Park Dae-Jin;Shin Yo-An
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.43 no.3 s.345
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    • pp.1-9
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    • 2006
  • In this paper, we propose a MIMO-OFDMA (Multi Input Multi Output-Orthogonal Frequency Division Multiple Access) system based on beamforming for performance improvement of downlink real-time traffic transmission in harsh channel conditions with low CIR (Carrier-to-Interference Ratio). In the proposed system, we first consider the M-GTA-SBA (Modified-Grouped Transmit Antenna-Simple Bit Allocation) using effective CSI (Channel State Information) calculation procedure based on spatial resource grouping, which is adequate for the combination of MRT (Maximum Ratio Transmission) in the transmitter and MRC (Maximum Ratio Combining) in the receiver. In addition, to reduce feedback information for the beamforming, we also apply QEGT (Quantized Equal Gain Transmission) based on quantization of amplitudes and phases of beam weights. Furthermore, considering multi-user environments, we propose the P-SRA (Proposed-Simple Resource Allocation) algorithm for fair and efficient resource allocation. Simulation results reveal that the proposed MIMO-OFDMA system achieves significant improvement of spectral efficiency in low CRI region as compared to a typical open-loop MIMO-OFDMA system using pseudo-orthogonal space time block code and H-ARQ IR (Hybrid-Automatic Repeat Request Incremental Redundancy).

Development of Microwave Water Surface Current Meter for General Use to Increase Efficiency of Measurements of River Discharges (하천유량측정의 효율성 향상을 위한 범용 전자파표면유속계 개발)

  • Kim, Youngsung;Noh, Joonwoo;Choi, Kwangsoon
    • Korean Journal of Ecology and Environment
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    • v.47 no.3
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    • pp.225-231
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    • 2014
  • Discharge measurement during flood season is very difficult. Microwave water surface current meter (MWSCM) can measures river surface velocities easily without contacting water. This study introduces its improved version, MWSCM for general use. The existing version of MWSCM is for floods so that its applicable period in a year is short. It has been improved to extend its applicability in a year. The range of measurable velocity for MWSCM for general use is extended so it can be applied during normal flows as well as high flows. MWSCM for general use can measure the velocity range of $0.03{\sim}20.0ms^{-1}$, whereas MWSCM for floods can measure the velocity range of $0.5{\sim}10.0ms^{-1}$. To make such innovation of MWSCM for general use, the applied microwave frequency of MWSCM was changed from 10 GHz to 24 GHz. Waveguide slot array antenna has been designed with the new development of the circuit of transmitting and receiving part. Improvement requests on the existing MWSCM for floods - weight lightening, measured velocity stabilization, self-test, low power consumption, and waterproof and dampproof - from the users of it have been reflected for the development of the new version of MWSCM.

Tunable Dielectric Properties and Curie Temperature with BST Thick Films (BST 후막의 가변 유전특성과 큐리온도에 관한 연구)

  • Kim In-Sung;Song Jae-Sung;Min Bok-Ki;Jeon So-Hyun
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.8
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    • pp.392-398
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    • 2006
  • The properties of tunable dielectric materials on RF frequency band are important high tunability and low loss for RF variable devices, variable capacitor, phased array antenna and other components application. Various composite of BST(barium strontium titanate) ratio combined with other non-electrical active oxide ceramics have been formulated for such uses. We present the tunable properties and Curie temperature on BST thick films. The grain growth of the weight ratio of $BaTiO_3$ increased. This can be explained by the substitute $Sr^{2+}$ ion for $Ba^{2+}$ ion in the $BaTiO_3$ system. The Curie temperature was shifted to lower temperature with increasing $SrTiO_3$in the $BaTiO_3-SrTiO_3$ system, because of decreasing the lattice constant. Also, the dielectric constant, tunability and K-factor of $(Ba_xSr_{1-x})TiO_3$ at over the Curie temperature decreased, at over the $60^{\circ}C$ fixation, maximum dielectric constant at Curie temperature and hence sharper phase transformation occurred at Curie temperature. The result were interpreted as a process of internal stress relaxation resulting form the increase of $90^{\circ}$ domains induced the BST. As a result, It is concluded that over the Curie temperature, frequency response and DC field effect for the tunable properties of BST thick film are suppressed by the transition broadening. For the application of tunable devices, that the curie temperature was investigated to be increased.

Current Status of Ceramic Composites Technology for Space Vehicle (우주비행체용 세라믹 복합재료 해외기술 동향)

  • Lee, Ho-Sung
    • Current Industrial and Technological Trends in Aerospace
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    • v.7 no.2
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    • pp.76-84
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    • 2009
  • In this review an attempt is made to give the background to the current trends in foreign developments in the ceramic matrix composites for space vehicles. The lightweight and high temperature specific modulus properties of ceramic composites have continued to develop for designing advanced propulsion structures and for increasing space vehicle performances. Those applications require advanced materials with good resistance to high temperatures, to oxidation environments and to mechanical stresses. The advantages of ceramic matrix composites are the low specific weight, the high specific strength over a wide temperature ranges, and their good damage tolerance compared to tungsten, pyrographites and polycrystalline graphites. Due to these advantages ceramic matrix composites are currently used in rocket engine chamber, nozzle, solar array, radar antenna, mirror support structures, hypersonic leading edge articles, heat shields, reentry vehicle nose tips, and radiators for spacecraft. Various processes are discussed together with examples of current application so that some of the advanced technologies can be possibly applied to Korean space technology.

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A Study on Development of the High-Power Low-Loss Waveguide Circulator for Ka-band Millimeter-Wave Seeker (밀리미터파대역(Ka-대역)탐색기용 고 전력 저 손실 도파관 순환기 개발에 관한 연구)

  • Jung, Chae-Hyun;Han, Sung-Min;Baek, Jong-Gyun;Lee, Kook-Joo;Park, Chang-Hyun;Kwon, Jun-Beom
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.17 no.6
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    • pp.83-88
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    • 2017
  • In this paper, a 3-port waveguide circulator of Ka-band millimeter-wave for isolation between transmit channel and receive channel at high power transmit mode is designed and fabricated for the seeker of the guided missile and circulator performance is verified through the S-parameter, high power and operation temperature test. At the configuration design, interface design between a seeker antenna and the circulator is considered and half-height of standard waveguide is applied for minimum and light weight body. The shape of permanent magnet and ferrite is optimized by simulation and tuning dielectrics at each port are placed for the best performance. In Fc(center frequency)${\pm}1000MHz$, designed waveguide circulator has below -20 dB return loss, below 0.5 dB insertion loss and below -23 dB isolation. It is found that circulator characteristics is similar to design results.

A Study on the High-power Low-loss Dual Axes Waveguide Rotary Joint for Ka-Band Millimeter-Wave Small Radar (밀리미터파대역(Ka-대역)소형 레이더용 고 전력 저 손실 2축 도파관 로터리 조인트 연구)

  • Jung, Chae-Hyun;Sung, Jong-Hyun;Baek, Jong-Gyun;Lee, Kook-Joo;Park, Chang-Hyun;Kwon, Jun-Beom
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.18 no.1
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    • pp.91-96
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    • 2018
  • In this paper, dual axes waveguide rotary joint, which operates at high power and has low loss characteristic, is designed and fabricated for a Ka-band millimeter-wave small radar. Its electrical performance is verified through the S-parameter at room temperature, high power and operation temperature test. Rotary joint functionally consists of the mode converter transforming rectangular waveguide into circular waveguide and the choke at the rotation part. At the configuration design, linking a fixed transmitter to an antenna rotating dual axes electrically for minimum loss and light weight body are considered. In Fc(center frequency)${\pm}500MHz$, the designed rotary joint has VSWR 1.5:1 below return loss, -2.0 dB above insertion loss. It is found that rotary joint characteristics is similar to design results.

Design of a Higher-Order Mode Coupler Using Coaxial-Structure Waveguide for Ku-Band Monopulse Satellite Tracking (Ku대역 모노펄스 위성추적을 위한 동축구조 도파관 고차모드 커플러 설계)

  • Ga, Deuk-Hyeon;Park, Do-Hyun;Song, Choong-Ho;Ahn, Sung-Joon;Jun, Chan-Won;Lee, Jae-Moon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.39C no.4
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    • pp.380-386
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    • 2014
  • In this paper, a higher-order mode coupler using coaxial-structure waveguide for Ku-band monopulse satellite tracking is proposed. The proposed higher-order mode coupler is built in a coaxial structure for compactness and weight reduction, making it suitable for mobile tracking systems. The inner circular waveguide of coaxial-structure is used to extract the fundamental mode signal and the high-order mode signal is extracted from the four slots of the outer circular waveguide and then transmitted via given stepped rectangular waveguide structure. The simulated results show that proposed higher-order mode coupler covers 250 MHz(12.75 GHz ~ 13.00 GHz) bandwidth with return loss and insertion loss characteristics. The antenna patterns of fundamental mode and higher-order mode applicable to monopulse tracking are generated successfully. Designed higher-order mode coupler using coaxial waveguide structure for Ku-band is expected to be used for high precision monopulse satellite tracking systems.