• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.11
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• pp.1020-1026
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• 2015

In this paper, the design of longitudinal shunt slot array monopulse antenna in the broad wall of waveguide for Ka band millimeter-wave seeker, Dip-Brazing method for fabrication and experiment results are presented. The proposed antenna consists of radiating slots by using Elliot's array synthesis procedure, probe-exciting feed structure for improving the return loss bandwidth and monopulse comparator. Element weigthings in the array have been calculated by continuous Taylor aperture distribution. Also, the simulation tool has been used to characterize the individual isolated slot, which has subsequently been used in Elliot's method to design the slot array efficiently. The designed antenna is fabricated using Dip-Brazing method. The gain of measured antenna is 28.4 dBi. Antenna beamwidth and side lobe levels are similar to the design result we expect.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.9
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• pp.13-20
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• 1999

A 2-stage MMIC(monolithic Microwave Integrated Circuits) LNA(Low Noise Amplifiers) at 30GHz hand has been designed and fabricated for the Ka-band Satellite Communications. The $0.15 {\mu}m$ with the width of $80 {\mu}m$ pHEMT technology was used for the fabrication of this MMIC LNA. Using the series feedback technique, ultra low noise and excellent S11 could be obtained at the same time without the cost of gain at 30GHz-band. The stability factors(Ks) for each stage and overall stage are greater than 1 at full frequency bands by the bias circuits and stabilization circuit. The measured performances, which agree well with the predicted performances, show this 2-stage MMIC LNA has the gain of more than 15.7dB and noise figure of less than 2.09dB over 29GHz to 33GHz.

• ETRI Journal
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• v.27 no.1
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• pp.43-52
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• 2005

In this paper, we introduce an adaptive radio resource allocation for IP-based mobile satellite services. We also present a synchronous multibeam CDMA satellite system using an orthogonal resource sharing mechanism among downlink beams for the adaptive packet transmission. The simulation results, using a Ka-band mobile satellite channel and various packet scheduling schemes, show that the proposed system and resource allocation scheme improves the beam throughput by more than two times over conventional systems. The simulation results also show that, in multibeam satellite systems, a system-level adaptation to a user's channel and interference conditions according to user locations and current packet traffic is more efficient in terms of throughput improvement than a user-level adaptation.

• Journal of IKEEE
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• v.3 no.1 s.4
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• pp.1-10
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• 1999

In this paper, the design for the shaped offset cassegrain antenna system combined with corrugated feed horn is presented. First, spherical-mode wave theory is applied to the corrugated conical horn and its radiation patterns are investigated. Using the radiation patterns, design data of the corrugated conical horn are obtained by efficiency investigation of horn antenna. When the investigation is completed, the flare angle and length of the corrugated conical horn is determined. Next, the main and sub-reflector is designed using Snellis law and the conservation principle of energy. Then the uniform direction and energy density of the traveling wave at the aperture of the main-reflector is obtained. The maximum size of the main-reflector is determined by investigation of the illumination and spillover efficiency. Finally, the curvature of the main-reflector is modified to satisfy the condition of the uniform phase. From the calculated efficiencies, the designed site of the main-reflector and sub-reflector, system gain of the shaped offset cassegrain antenna has been obtained 40.5dB in Ka-band frequency. It has better characteristics than the result of SABOR with 39dB gain.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.25.3-25.3
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• 2011

지구 또는 우주 원격탐사 및 관측에서 진일보한 임무 수행을 위해 위성 편대 비행의 필요성이 점차 부상하고 있다. 편대 비행은 단일 위성으로는 실현하기가 어렵거나 불가능한 과학적인 임무를 수행할 수 있다. 다양한 위성 편대 비행 기술에서 중요한 기술 중에 하나는 편대 위성간의 정밀기선결정 기술이며, 정밀도 검증 기술도 함께 동반되어야 한다. 이 논문에서는 Gravity Recovery and Climate Experiment(GRACE) 위성의 실제 Global Positioning System(GPS) 데이터를 사용하여 GRACE A와 B 두 위성의정밀기선결정을 수행하였다. 그리고 K/Ka-Band Ranging system(KBR) 바이어스 거리측정값으로 일괄처리 및 순차처리 방법을 통해 정밀도를 검증하였다. 제안된 순차처리 방법은 KBR 바이어스를 추정하는 대신에 기산점 차분으로 이를 제거하여 정밀도를 검증하기 때문에 검증자(KBR baised range)가 피검증자(GPS-baseline)와 독립적이고 실시간 정밀도 검증에 적용이 가능하다. 그 결과 일괄처리 검증방법과 유사한 1.5 ~ 3.0 mm의 순차처리 정밀도 검증 결과를 얻었다.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.15-20
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• 2000

We demonstrated a single balanced mixer of the combination of high-T. superconductor (HTS) and III-V GaAs beam lead Schottky diodes operating in the mini-cryogenic chamber. The HTS hybrid mixer was designed with a center frequency of 27.5 GHz and a bandwidth of 1 GHz, and consisted of a rat-race coupler circuit with beam-lead diodes attached to its balanced ports. The HTS hybrid mixer with 1 GHz RF bandwidths exhibits a conversion loss of 6 dB. A LO-to-RF isolation was greater than 40 dB in the range of operating frequencies. Since the HTS/III-V hybrid mixer devices have lower noise and conversion loss, this technique provide us with new capabilities that can be effectively utilized in the field of local-point distribution service (LMDS) systems.

• Journal of Electrical Engineering and Technology
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• v.5 no.1
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• pp.151-155
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• 2010

Reconfigurable radio technology is needed to reconstruct frequency and modem functionality, which can be different in various regions. In addition, it makes a single mobile handset capable of supporting various standards of wireless communication and thus plays a key role in mobile convergence. An MMIC VCO (voltage controlled oscillator) has been developed for high power and wide bandwidth where Clapp-Gouriet type oscillators are adapted for series feedback, and was fabricated based on 0.15um pHEMT of TRW. The MMIC VCO was connected to an aluminar substrate on the carrier for testing. This MMIC VCO module showed good performance in comparison to existing works. Furthermore, it can be potentially extended to reconfigure an MMIC VCO for wireless systems such as military applications and satellite communications.

• Journal of Satellite, Information and Communications
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• v.1 no.2
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• pp.25-31
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• 2006

The COMS (Communication, Ocean, and Meteorological Satellite) performing meteorological and ocean monitoring and providing communication service with meteorological, ocean and Ka-band payload in the geostationary orbit includes MODCS (Meteorological and Ocean Data Communication Subsystem) which provides transmitting the raw data collected by meteorological payload called MI (Meteorological Imager) and ocean payload named GOCI (Geostationary Ocean Color Imager) to the ground station and relaying the meteorological data processed on the ground to the end-user stations. MODCS comprises of two channels: SD channel which formats the raw data according to CCSDS recommendation, amplifies and transmits its signal to the ground station; MPDR channel which relays to the end-user stations the ground-processed meteorological data in the data format of LRIT/HRIT recommended by CGMS. This paper constructs the architecture of MODCS for transmitting and relating the observed data, and investigates that the key performance parameters have the required margin through the preliminary performance analyses.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.8
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• pp.766-773
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• 2016

This paper proposes an aircraft-installed compact offset-parabolic-reflector antenna for the spinning direction-finding applications. The feeder of the reflector antenna is a LPDA antenna that has the ultra-wideband characteristics and the $45^{\circ}$ slant linear polarization. The reflector is designed to be slanted by $5^{\circ}$ in the elevation and to be small in size on the basis of the reference parabolic shape for the purpose of the high gain and mounting on the underside of aircraft fuselage. Over the ultra-wideband 20:1 bandwidth from S to Ka band, the measured average gain of the proposed antenna is 27.97 dBi, and the average half-power beam width is $4.55^{\circ}$ in the azimuth and $4.3^{\circ}$ in the elevation which is the pencil-beam radiation pattern. All the measured data are similar to the simulation results. The designed compact offset-parabolic-reflector antenna that is installed in the limited area has the ultra-wideband and high-gain characteristics. We expect that the newly designed antenna can be applied to the spinning direction-finding antenna system installed in an aircraft.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.357-365
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• 2013

The 4 by 4 series slot sub-array antenna is proposed using substrate integrated waveguide(SIW) technology for 35 GHz of Ka band application. The proposed antenna is realized with multi-layered structure for compact size and easy integration features. 4 by 4 radiating slots are arrayed on top PCB with equal spacing and the feeding SIWs are arranged on middle and bottom PCBs for uniform power distribution. The multi-layered antenna is realized using RT/Duroid 5880 that has dielectric constant of 2.2 and the total antenna size is $750.76mm^2$. The individual parts such as radiators and feeding networks are simulated using full-wave simulator CST MWS. Furthermore, the total sub-array antenna also fabricated and measured the electrical performances such as impedance bandwidth under the criteria of -10 dB(490 MHz), maximum gain(18.02 dBi), sidelobe level(SLL)(-11.0 dB), and cross polarization discrimination (XPD)(-20.16 dB).