• Journal of the Korea Institute of Military Science and Technology
• /
• v.23 no.3
• /
• pp.221-228
• /
• 2020

This paper presents the radar counter jamming algorithm and ground far-field test results for the pull-off deceptive jamming signals like RGPO(Range Gate Pull Off) and VGPO(Velocity Gate Pull Off). We designed the radar counter jamming algorithm according to the characteristics of the deceptive jamming signals. This algorithm is validated by simulation before ground far-field test. The existing X-band AESA radar demonstrator was used to test the proposed algorithm. The proposed algorithm was applied to the radar processor software. The deceptive jamming signals generated using the commercial jamming signal generator. We performed the repeated ground far-field test with the test scenario. Test results show that the proposed counter deceptive jamming algorithm works in the real radar system.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.9
• /
• pp.2362-2372
• /
• 1996

This paper deals with the design and development of an Injection-Locking Coupled Oscillators(ILCO), which functions like phase-shifter in the Active Intergrated Phased Array Antenna(AIPAA). This linear array 2-element ILCO consists of two Injection Locking Hair-pin Resonator Oscillators(ILHRO) and an unilateral amplifier. The first and second elements of the ILCO have same frequency tuning range but locking bandwidths of 11.5MHz and 14MHz respectively. A phase shift of .DELTA..PHI.=158.4.deg.(-78.0.deg. to 80.4.deg.) could be obtained inthe second element of ILCO when the first elementof the ILCO was in the reference locking mode(.DELTA..PHI.=0.deg.). When the ILCO is applied to the AIPAA, the predicted beam scanning angle value will be 38.4.deg.. Each ILCO gives good frequency stability and lower AM, FM, and PM noise charactheristics in the mutual coupling lockingmode. The ILCO can not only play a part as the phase shifter for the AIPAA but it can also be usedas the power combining device in the mm-wave frequency range and as a part of a T/R MMIC module.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.27 no.4
• /
• pp.313-320
• /
• 2014

A tensegrity structure consists of a set of continuous cables in tension and a set of discontinuous struts in compression. The tensegrity structure can be classified into self-stressed and pre-stressed pin-jointed structure. A key step in the design of tensegrity structures is the determination of their equilibrium configuration, known as form-finding. In this paper, three effective methods are presented for form-finding of tensegrity structures. After performing form-finding process, a set of force density and corresponding topology results can be obtained. Then the force density method combined with a genetic algorithm is adopted to uniquely define a single integral feasible set of force densities. Numerical examples are presented that demonstrate the excellent performance of the algorithms.

• Journal of Applied Reliability
• /
• v.17 no.3
• /
• pp.236-245
• /
• 2017

Purpose: There is no established inspection system for composite wind blade during the fabrication stage even though the blades are one of the most important part at wind generation system, but phased array ultrasonic testing method has been continuously studied about wind turbine blade with composite. When wind turbine blade with complex shape by phased array probe is inspected, it is necessary to study for system keeping constant pressure using pressure device. Methods: In this paper, we propose constant pressure device for inspecting wind turbine blade by phased array ultrasonic test method. Design of the device controller is based on Hunt-Crossley model. We evaluate reliability of phased array ultrasonic inspection result that applicated constant pressure device. Result: Defect indication is precise and its error is small when constant pressure mechanism based on Hunt-Crossley model was used. Conclusion: When inspection is progressed using constant pressure mechanism, the reliability of composite wind blade inspection can be improved.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.1
• /
• pp.67.1-67.1
• /
• 2011

태양으로부터 날아오는 고에너지 하전 입자들은 인공위성이나 지구의 통신장비에 심각한 고장을 일으킬 수 있다. 이런 사고를 방지하기 위해서는 사전에 태양풍의 물리량을 알아내는 것이 중요하다. 이를 위해 inter planetary scintillation 현상을 이용하여 태양풍의 운동을 예보하는 시스템을 전파연구소와 협력하여 개발할 예정이다. 그 첫 단계로 이 시스템보다 작은 규모의 시제품을 만들어 동작을 입증하고자 한다. 이 시제품은 각각 16개의 다이폴 안테나로 구성된 타일 3개로 이루어져 있다. 다이폴 안테나들의 중심주파수는 350MHz이고, 대역폭은 약10MHz이다. 48개의 다이폴 안테나들의 총 집광면적은 약 30m2이고, 타일 내의 다이폴 안테나들을 나선형으로 배열해 grating lobe의 크기를 감소시켰다. 각 안테나에서 나오는 신호는 저 잡음의 LNA를 이용해 증폭하여 beam former로 인가된다. Beam former는 안테나에서 나오는 신호의 위상을 조절하고 합쳐서 약 15도 크기의 빔을 만들고 전자적으로 천체를 추적한다. Beam former에서 나온 신호는 수신기에서 저주파의 신호로 변환되는데, 국부발진기를 조절하여 radio frequency interference에 능동적으로 대처할 수 있도록 하였다. 수신기에서 나오는 아날로그 신호는 digitizer를 최대 107sps의 빠르기로 2바이트의 디지털 신호로 전환된다. Labview 프로그램을 사용하여 3개의 타일에서 나온 신호를 합성해서 태양 근처의 전파원을 추적하도록 하였다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.22 no.5
• /
• pp.981-989
• /
• 1997

In this paper, the 5-element active phased array antennas coupled through slotline between elements are designed and fabricated. A recent studies on the active phased array antennas using the transmission line coupling which can be designed to provide strong coupling and the appropriate coupling phase. But this sturucture has limitation of expanding in two dimensions for planar active phased array antennas and distortion of the radiation pattern caused by coupling network. Thus our work proposes the slotline coupling structure asthe broadband coupling network for the active phased array antenna. In experiment, 5-elements active phased array antenas have steering range from -30.deg. to 20.deg. off broadside as the free-running frequencies of end elements are controlled. The overall results show that the proposed slotline coupling structure is suited for the coupling network in the actie phased array antenna system. And the proposed coupling structire solves the expansion problem and eliminates the distortion of the radiation pattern caused by the spurious radiation of the transmission line coupling network. Thus thiscan be expanded to two dimensional coupling network for the planar active phased array antenna system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.12 no.1
• /
• pp.125-135
• /
• 2001

A 8$\times$4 microstrip antenna array is designed at 5.3 GHz and its characteristics are investigated with respect to the application in dual polarized synthetic aperture radars. The design is focused on the achievement of a wide bandwidth, a high polarization purity, a low loss, a good isolation and some mechanical requirements suitable for the application. The antenna is fed by a -3 dB tapered feed network, and is composed of dual polarized SSFIP (Strip-Slot-Foam-Inverted Patch) elements with honeycomb and shielding plane. Simulation results for the antenna array are presented and compared with measurements. It is observed that the antenna shows a bandwidth of 80 MHz, a polarization isolation better than 20 dB, an isolation of 40 dB, and good mechanical characteristics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.8
• /
• pp.995-1001
• /
• 2012

This paper compares the performance of several tracking filters, namely, alpha-beta filter, Kalman filter and TBM tracking filter for ballistic target tracking problem using multi-function radar. Every of three tracking filters suggested was tested on simulator developed in accordance with TBM trajectory and MFR RSP measurement. The result shows the method using TBM tracking filter gives 75.3 % decreased velocity RMS error than alpha-beta filter. After initialization, the RMS error of range and velocity of the proposed filter is also smaller than the Kalman filter. Finally the proposed filter is suitable for high-speed TBM tracking due to the stable angle tracking accuracy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.28 no.11
• /
• pp.920-923
• /
• 2017

In this paper, we design the internal parameters of the SIMO channel sounder suitable for the measurement of the high-speed travel environment channel, and measure the characteristics of the wide-band channel by applying the proposed measurement method to the Yeoju Smart Highway piloted at 5.89 GHz C-ITS. Based on the design of the receiving array structure suitable for the real environment, the linear slope compensation method for the Doppler phase shift is applied to provide a reliable result on the Doppler effect due to the incoming angle information and the surrounding environment in the multipath environment.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.67 no.9
• /
• pp.1197-1201
• /
• 2018

In this paper, a Doppler radar for a localization of a human motion is demonstrated. In the system, we used a $8{\times}8$ phased array antenna using metamaterial phase shifters for easy and precise control of antenna beam pattern. Scanning area is a circular sector with an inscribed angle of $60^{\circ}$ and a diameter of 45m. This area is divided with 15 designated area and each area is scanned for 0.2 second. When there is a motion in a designated area, we are able to detect a frequency shift due to a Doppler effect. In this way it is possible to detect the location of motion. The experiment shows that 78% of position accuracy. The remaining 22% occurred the surroundings of the designated area.