• Journal of electromagnetic engineering and science
• /
• v.18 no.2
• /
• pp.117-128
• /
• 2018

In this paper, compact linear dual polarized series-fed $1{\times}2$ linear and $2{\times}2$ planar arrays antennas for airborne SAR applications are proposed. The proposed antenna design consists of a square radiating patch that is placed on top of the substrate, a quarter wave transformer and $50-{\Omega}$ matched transformer. Matching between a radiating patch and the $50-{\Omega}$ microstrip line is accomplished through a direct coupled-feed technique with the help of an impedance inverter (${\lambda}/4$ impedance transformer) placed at both horizontal and vertical planes, in the case of the $2{\times}2$ planar array. The overall size for the prototype-1 and prototype-2 fabricated antennas are $1.9305{\times}0.9652{\times}0.05106{{\lambda}_0}^3$ and $1.9305{\times}1.9305{\times}0.05106{{\lambda}_0}^3$, respectively. The fabricated structure has been tested, and the experimental results are similar to the simulated ones. The CST MWS simulated and vector network analyzer measured reflection coefficient ($S_{11}$) results were compared, and they indicate that the proposed antenna prototype-1 yields the impedance bandwidth >140 MHz (9.56-9.72 GHz) defined by $S_{11}$<-10 dB with 1.43%, and $S_{21}$<-25 dB in the case of prototype-2 (9.58-9.74 GHz, $S_{11}$< -10 dB) >140 MHz for all the individual ports. The surface currents and the E- and H-field distributions were studied for a better understanding of the polarization mechanism. The measured results of the proposed dual polarized antenna were in accordance with the simulated analysis and showed good performance of the S-parameters and radiation patterns (co-pol and cross-pol), gain, efficiency, front-to-back ratio, half-power beam width) at the resonant frequency. With these features and its compact size, the proposed antenna will be suitable for X-band airborne synthetic aperture radar applications.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.17 no.3
• /
• pp.326-332
• /
• 2017

A switched VCO-based UWB transmitter for 3-5 GHz is implemented using $0.18{\mu}m$ CMOS technology. Using RF switch and timing control of DPGs, the uniform RF power and low power consumption are possible regardless of carrier frequency. And gate control of RF switch enables the undesired side lobe rejection sufficiently. The measured pulse width is tunable from 0.5 to 2 ns. The measured energy efficiency per pulse is 4.08% and the power consumption is 0.6 mW at 10 Mbps without the buffer amplifier.

• Proceedings of the KAIS Fall Conference
• /
• 2010.11a
• /
• pp.168-171
• /
• 2010

본 논문에서는 GaN HEMT 소자를 이용한 고출력 고효율 특성을 가지는 광대역 SSPA의 개발을 다루고 있다. 개발한 SSPA는 8W 급과 15W 급의 GaN HEMT 소자를 사용하여 Pre-Drive 증폭단을 구성하였으며, Drive 증폭단은 50W/150W급 GaN HEMT 소자를 직/병렬구조로 사용하였다. Main 증폭단은 4-way 분배기와 결합기를 이용한 Balanced Structure를 적용하여 높은 출력을 구현하였으며, 안정적인 동작을 위하여 음(-)전원 제어 회로와 출력신호 검출 회로를 포함하고 있다. 제작된 SSPA의 사용가능 대역은 2.9GHz~3.3GHz로 단일전원을 사용하고 있으며 100us 펄스 폭, 10% Duty Cycle 조건에서 60dB의 전압이득, 1kW 출력과 약 28% 효율 특성을 가지는 것으로 측정되었다. 본 논문에서 개발한 SSPA는 S-대역을 사용하는 레이더시스템의 송신단에 적용될 수 있다.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2005.06a
• /
• pp.423-428
• /
• 2005

We prepared paint-type and sheet-type EM wave absorbers with Mn-Zn Ferrite, Ni-Zn Ferrite, Ba Ferrite, Sr Ferrite, and Sendust against ghosts of a mater in ships. To prepare the absorbers, enamel paint and epoxy paint were used as binders. The prepared EM wave absorber's absorption properties were investigated. The prepared EM wave absorbers have 6 dB over in 2 GHz ${\sim}$ 4 GHz. We compared properties of wave absorption between paint-type and spray-type

• Journal of Advanced Navigation Technology
• /
• v.8 no.1
• /
• pp.57-65
• /
• 2004

In this paper, keeping pace with light weight, pocket-size, lower-price, we design VCO(Voltage Controlled Oscillator) X/Ku band for using at public RD(Radar Detector) to apply to controlled voltage on base in transistor which used as a oscillator, without using varactor diode in part of VCO tuner. As a result of simulation, we conclude VCO could be have 110 MHz by controlled voltage 4.25 V to 4.80 V and show its output 9.63 dBm at operating frequency, 11.46 GHz, and its phase noise -107.2 dBc at 1 MHz offset frequency. So it turned out suitable performance for commercial use.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.8 no.4
• /
• pp.906-911
• /
• 2004

In this paper, a VCDRO(Voltage Control Dielectric Resonator Oscillator) applied to FMCW(Frequency Modulated Continuous Wave)Radar as stable source is implemented and constructed with a MESFET(Metal-semiconductor Field-Effect Transistor) for low noise, a dielectric resonate. of high frequency selectivity, and high Q varator diode to obtain a good phase noise performance and stable sweep characteristics. The designed circuits is simulated thrash harmonic balance simulation technique to provide the optimum performance. The measured result of a fabricated VCDRO shows that output is 2.22㏈m at 12.05GHz, harmonic suppression -30㏈c, phase noise -130㏈c at 100KHz offset, and sweep range of varator diode $\pm$18.7MHz, respectively. This oscillator will be available to FMCW Radar.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.1
• /
• pp.76-79
• /
• 2016

This paper describes the successful development and the performance of X-band 50 W pulsed power amplifier using a 50 W GaN-on-SiC high electron mobility transistor. The GaN HEMT with a gate length of $0.25{\mu}m$ and a total gate width of 12 mm were fabricated. The X-band pulsed power amplifier exhibited an output power of 50 W with a power gain of 6 dB in a frequency range of 9.2~9.5 GHz. It also shows a maximum output power density of 4.16 W/mm. This 50 W GaN HEMT and X-band 50 W pulsed power amplifier are suitable for the radar systems and related applications in X-band.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.9 no.10
• /
• pp.1131-1137
• /
• 2014

In this paper, oscillator with compact hairpin resonator is used to design the local oscillator of X-band radar system. The proposed hairpin resonator is minimized by increasing capacitance of line end of conventional one. By this method, size can be minimized about 40% compared with the conventional resonator and also can improve phase noise characteristic. The result of oscillator using proposed hairpin resonator is measured in oscillating frequency of 9.05 GHz, output power of 2.47 dBm, and phase noise of -101.4 dBc/Hz. The fabricated oscillator in this paper can minimize design and it's planar structure makes it easy to design MMIC.

• Proceedings of the KIEE Conference
• /
• 2008.10b
• /
• pp.478-479
• /
• 2008

본 연구에서는 비접촉 방식으로 심박과 호흡을 측정하기 위해 2.4GHz 대역에서 동작하는 도플러 레이더 센서와 베이스밴드 모듈로 구성된 도플러 레이더 시스템을 설계하고 그 성능을 평가하였다. 설계된 도플러 레이더 시스템은 심폐활동에 의한 흉부 표면의 움직임에 의해 반사되는 레이더의 위상변화를 이용하여 심폐 활동을 측정한다. 도플러 레이더 센서의 출력은 베이스 밴드 모듈의 전처리 필터부, 증폭부, 오프셋 조정부를 통과하여 호흡과 심박 신호로 분리된다. 분리된 생체신호는 기존의 생체신호와 상관성을 확인하기 위해 기준신호로 호흡과 심전도를 동시에 측정하여 그 결과를 비교 및 분석하였다. 설계된 도플러 레이더 시스템에서 분리된 호흡 및 심박 신호는 측정 대상의 움직임이 없는 상태에서는 높은 검출률을 보였으며, 도플러 레이더에서 심박과 호흡 신호를 검출한 결과 거리, 호흡과 심박의 변이량, 호흡과 심박대역에 따라 검출률이 영향을 받는다는 것을 알 수 있었다.

• Korean Journal of Remote Sensing
• /
• v.35 no.1
• /
• pp.29-37
• /
• 2019

Synthetic Aperture Radar (SAR) observations are powerful tools to monitor surface's displacement very accurately, induced by earthquake, volcano, ground subsidence, glacier movement, etc. Especially, radar interferometry (InSAR) which utilizes phase information related to distance from sensor to target, can generate displacement map in line-of-sight direction with accuracy of a few cm or mm. Due to decorrelation effect, however, degradation of coherence in the InSAR application often prohibit from construction of differential interferogram. Offset tracking method is an alternative approach to make a two-dimensional displacement map using intensity information instead of the phase. However, there is limitation in that the offset tracking requires very intensive computation power and time. In this paper, efficiency of parallel computing has been investigated using high performance computer for estimation of glacier velocity. Two TanDEM-X SAR observations which were acquired on September 15, 2013 and September 26, 2013 over the Narsap Sermia in Southwestern Greenland were collected. Atotal of 56 of 2.4 GHz Intel Xeon processors(28 physical processors with hyperthreading) by operating with linux environment were utilized. The Gamma software was used for application of offset tracking by adjustment of the number of processors for the OpenMP parallel computing. The processing times of the offset tracking at the 256 by 256 pixels of window patch size at single and 56 cores are; 26,344 sec and 2,055 sec, respectively. It is impressive that the processing time could be reduced significantly about thirteen times (12.81) at the 56 cores usage. However, the parallel computing using all the processors prevent other background operations or functions. Except the offset tracking processing, optimum number of processors need to be evaluated for computing efficiency.