• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.28 no.5
• /
• pp.410-418
• /
• 2017

Results of an analysis of the continuous motion effect for FMCW-SAR system and a signal processing to correct it are presented in this paper. SAR images reconstructed by back-projection algorithm are included as well. To analyze how platform velocity and sampling frequency affect the continuous motion effect, FMCW signal model was used, and the signal processing in time-doppler(t, $k_u$) domain was adopted. Then, back-projection algorithm and modified matched-filter was used to reconstruct SAR images, and it was validated using measured data by airborne FMCW-SAR system in X-band frequency.

• Proceedings of the KSRS Conference
• /
• 2008.10a
• /
• pp.340-343
• /
• 2008

The Soya Warm Current (SWC) is a coastal boundary current, which flows along the coast of Hokkaido in the Sea of Okhotsk. Seasonal and subinertial variations in the SWC are investigated using data obtained by high-frequency (HF) ocean radars, coastal tide gauges, and a bottom-mounted acoustic Doppler current profiler (ADCP). The HF radars clearly capture the seasonal variations in the surface current fields of the SWC. The velocity of the SWC reaches its maximum, approximately 1 m/s, in the summer, and becomes weaker in the winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately 50 km. The almost same seasonal cycle was repeated in the period from August 2003 to March 2007. In addition to the annual variation, the SWC exhibits subinertial variations with a period from 10-15 days. The surface transport by the SWC shows a significant correlation with the sea level difference between the Sea of Japan and Sea of Okhotsk for both of the seasonal and subinertial variations, indicating that the SWC is driven by the sea level difference between the two seas. Generation mechanism of the subinertial variation is discussed using wind data from the European Centre for Medium-range Weather Forecasts (ECMWF) analyses. The subinertial variations in the SWC are significantly correlated with the meridional wind component over the region. The subinertial variations in the sea level difference and surface current delay from the meridional wind variations for one or two days. Continental shelf waves triggered by the meridional wind on the east coast of Sakhalin and west coast of Hokkaido are considered to be a possible generation mechanism for the subinertial variations in the SWC.

• Journal of the Institute of Convergence Signal Processing
• /
• v.19 no.1
• /
• pp.28-34
• /
• 2018

This paper is composed of a passenger management system using a temperature sensing module, a PIR sensor module for detecting movement inside a room, and a smart breath sensing module for determining a sleeping state. An embedded sensor module and a communication system integrated the sensing part and the algorithm driving part. As the aging society is accelerating and becoming more upgraded, the social cost of Silver Care increases, and in order to protect privacy, it is necessary to reduce costs by developing efficient smart silver care devices. The proposed non - image human body detection IOT sensor system is implemented by hardware and software and has superior performance compared with conventional image monitoring method.

• The Journal of Korean Institute of Information Technology
• /
• v.16 no.11
• /
• pp.61-68
• /
• 2018

This paper describes design of a 10.525 GHz self oscillating mixer semiconductor IC chip combining voltage controlled oscillator and frequency mixer using silicon CMOS technology for Doppler radar applications. The p-core type VCO included in the self oscillating mixer minimizes the noise contained in the transmitted signal. This noise minimization increases the sensing distance and acts in a direction favorable to the reaching distance and the sensitivity of the motion detection sensor. Simulation results for phase noise show that a VCO designed as a P-core has a noise characteristic of -106.008 dBc / Hz at 1 MHz offset and -140.735 dBc / Hz at 25 MHz offset compared to a VCO designed with N-core and NP-core showed excellent noise characteristics. If a self-oscillating mixer is implemented using a p-core designed VCO in this study, a motion sensor with excellent range and reach sensitivity will be produced.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.30 no.5
• /
• pp.389-398
• /
• 2019

In this paper, we propose a method to detect small unmanned aerial vehicles(UAVs) flying in a real-world environment. Small UAV signals are frequently obscured by clutter signals because UAVs usually fly at low altitudes over urban or mountainous terrain. Therefore, to obtain a desirable detection performance, clutter signals must be considered in addition to noise, and thus, a performance analysis of each clutter removal technique is required. The proposed detection process uses clutter removal and pulse integration methods to suppress clutter and noise signals, and then detects small UAVs by utilizing a constant false alarm rate detector. After applying three clutter removal techniques, we analyzed the performance of each technique in detecting small UAVs. Based on experimental data acquired in a real-world outdoor environment, we found it was possible to derive a clutter removal method suitable for the detection of small UAVs.

• Korean Journal of Remote Sensing
• /
• v.35 no.3
• /
• pp.389-400
• /
• 2019

Level meters are non-invasively capable of measuring the level of the medium, and a growing variety of level meters are being used in the industry in connection with safety and maintenance. The level meter can be measured according to various kinds of medium such as solid medium such as coal, flour, rice and liquid medium such as water and petroleum. In order to reduce the error depending on the medium, the measurement using the Doppler Effect can compensate the measurement error, However, the number of signal processing steps is increased, the operation speed is further increased, the hardware complexity increases, and a high cost structure is required. In this paper, we propose a method to improve the signal processing operation structure of the remote measurement level meter to reduce the amount of computation and the resource usage of the required FPGA.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.82-82
• /
• 2023

홍수기 하천에서 유량측정은 예산, 인력, 안전 및 측정 시 편의성 등의 이유로 측정에 제한이 많다. 특히, 태풍 등으로 인한 호우사상 발생 시 위와 같은 문제로 홍수량 측정에 어려움이 따른다. 이러한 문제점을 개선하기 위해 Lee et al.(2021)은 드론과 전자파표면유속계의 기능을 융합한 DSVM(Dron and Surface Veloctity Meter using doppler radar) 측정방법을 개발하였다. 전자파표면유속계 측정의 제한 요소인 진동을 감소시키기 위해 댐퍼플레이트를 개발하였고 금강의 지류인 봉황천에 현장 적용을 통해 DSVM 측정방법의 실용성을 확인하였다. 기존 연구에서 DSVM 방법은 드론의 각 측선 이동을 위한 조종과 전자파표면유속계 측정의 제어를 측정자가 수행하였는데 본 연구에서는 통합 드론측정시스템(IDMS, Integrated Drone Measurement System) 개발을 통해 측정자의 조종 의존도를 줄임과 동시에 안전하고 정확한 유량측정을 위해 노력하였다. 기존 댐퍼플레이트의 상하 진동 흡수 기능뿐만 아니라 전자파표면유속계의 흔들림 현상 등 자세 제어 기능을 보완하기 3축 모터를 적용한 방수짐벌을 개발하여 측정 정확도를 향상시켰다. 미션컴퓨터 개발로 측정지점의 측정 임무정보를 DB화하여 각 측선별 헤딩, 고도, 이동 등 자동항법 기능과 기체의 안정화 이후 전자파표면유속계를 자동으로 제어하여 측정을 실시하는 기능을 구현하였다. 또한 통합 GCS(Ground Control System)를 통해 비행 및 측정에 대한 모든 정보를 확인하고 컨트롤 할 수 있게 하였다. 2022년 금산군(제원대교), 무주군(취수장), 경주시(서천교) 지점에서 홍수기 유량측정에 도입하여 중간단면적법, 지표유속법을 적용하여 통합드론측정시스템의 실용성을 검증 완료하였다. 2023년 현장에 18대의 통합 드론측정시스템을 도입하여 홍수기 유량측정에 활용할 계획이다.

• Journal of Korea Water Resources Association
• /
• v.45 no.9
• /
• pp.853-860
• /
• 2012

It is well-known that loop effect of the stage-discharge relationship is formulated based on many field observations especially for the sand rivers. Theoretical understandings of the loop effect for the sand rivers have been widely provided, based on the facts that it is driven by the flood wave propagation and bed form changes over the given flood period. However, very few theoretical studies or field observations associated with loop-rating curves in the gravel or rock-bed mountain streams have been attempted so far, due particularly to the difficulties in the accurate discharge measurement during the flood in such field conditions. The present paper aims to report a unique loop-rating curve measured at a gravel and rock-bed mountain stream based on the flood discharge observation acquired during the typhoon, Muifa that passed nearby Jeju Island in summer of 2011. As velocity instrumentation, a non-intrusive Surface Velocity Doppler Radar to be suitable for the flood discharge measurement was utilized, and discharges were consecutively measured for every hour. Interestingly, the authors found that the hysteresis of the loop-rating curve was adverse compared to the typical trend of the sand bed streams, which means that the discharge of the rising limb is smaller than the falling limb at the same stage. We carefully speculate that the adverse trend of the loop-rating curve in the gravel bed was caused by the bed resistance change that works differently from the sand bed case.

• Journal of the Korean Magnetics Society
• /
• v.25 no.3
• /
• pp.83-86
• /
• 2015

Nowadays the weapon systems are employed air bursting munition (ABM) as smart programmable 40 mm shells which have been developed in order to hit the target with programmed munition that can be air burst after a set distance in the battlefield. In order to improve the accuracy of such a bursting time, by measuring the speed of the munition from the barrel, weapon systems calculate the exact time of flight to the target and then the time information must be inputted to the munition. In this study, we introduce a device capable of detecting a shot at K4 40 mm automatic grenade. The shot is composed of a rotating copper band to convert linear motion into rotary motion when it passes through the barrel, the steel section is exert the effect of fragment and aluminum section to give fuze information. The aluminum section was used to detect munition using eddy current method. To measure muzzle velocity by means of non-contact method, two eddy current probes separated 10 cm was employed. Time interval between two eddy current probe detection times was used as muzzle velocity. The eddy current probe was fabricated U-shape Mn-Zn ferrite core with enamelled copper wire, and 200 kHz alternating current was used to detect inductance change. Measured muzzle velocity using the developed sensor was compared to the Doppler radar system. The difference was smaller than 1%.