• Korean Journal of Remote Sensing
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• v.34 no.6_3
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• pp.1383-1398
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• 2018

Sea surface wind is one of the most fundamental variables for understanding diverse marine phenomena. Although scatterometers have produced global wind field data since the early 1990's, the data has been used limitedly in oceanic applications due to it slow spatial resolution, especially at coastal regions. Synthetic Aperture Radar (SAR) is capable to produce high resolution wind field data. KOMPSAT-5 is the first Korean satellite equipped with X-band SAR instrument and is able to retrieve the sea surface wind. This study presents the validation results of sea surface wind derived from the KOMPSAT-5 backscattering coefficient data for the first time. We collected 18 KOMPSAT-5 ES mode data to produce a matchup database collocated with buoy stations. In order to calculate the accurate wind speed, we preprocessed the SAR data, including land masking, speckle noise reduction, and ship detection, and converted the in-situ wind to 10-m neutral wind as reference wind data using Liu-Katsaros-Businger (LKB) model. The sea surface winds based on XMOD2 show root-mean-square errors of about $2.41-2.74m\;s^{-1}$ depending on backscattering coefficient conversion equations. In-depth analyses on the wind speed errors derived from KOMPSAT-5 backscattering coefficient data reveal the existence of diverse potential error factors such as image quality related to range ambiguity, discrete and discontinuous distribution of incidence angle, change in marine atmospheric environment, impacts on atmospheric gravity waves, ocean wave spectrum, and internal wave.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.680-687
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• 2018

Borehole radar is a radar used for underground resources and geological exploration purposes. It needs a high-speed sampler to transmit electromagnetic waves with a pulse width of several ns and to receive reflected waves of several tens to several hundreds of MHz reflected from the object to be surveyed. ETS (Equivalent-Time Sampling), which can achieve sampling performance of several GHz with a sampling frequency of several tens of MHz, is suitable for use as a sampler of a borehole radar receiver. In this paper, we propose a method to control the sampling clock delay, which is the most important factor in ETS sampler design, using four clocks with phase difference of $90^{\circ}$ for one clock source. The proposed method can reduce the time required to acquire the data within the set interval by 1/25 than the conventional method using the delay generator. When the implemented sampler is applied to the receiver of existing borehole radar, it is possible to accumulate 58 additional times due to the shortened sampling time. In addition, by using one delay control logic compared with the conventional method using several sampling clock delay control logic in order to satisfy the target sampling range, it is possible to omit the correction process which was necessary in the past. As a result, the structure of the system can be simplified and a uniform sampler can be realized.

• Electronics and Telecommunications Trends
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• v.28 no.2
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• pp.77-85
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• 2013

본고에서는 의료용, 보안용, 정밀거리 측위 등 다양한 분야에 응용이 가능한 근거리 고해상도 레이더 칩 기술에 대하여 소개한다. 먼저 근거리 고해상도 레이더 칩의 대표적인 구조와 동작원리에 대하여 기술하고 상용제품, 최신 논문에서 발표된 레이더 칩에 대하여 소개하였다. 고해상도를 얻기 위한 짧은 펄스 폭(나노초, 십억분의 1초)을 가지는 펄스를 송신하고 목표물을 맞고 되돌아온 에코 펄스를 고해상도로 수신하여 복원된 펄스로부터 얻어지는 거리정보로부터 신호처리 과정을 거쳐 고도화된 응용 분야에 따른 부가적인 정보를 얻는다. 수신기는 상관(correlation)법에 의한 수신 방식과 샘플링(sampling)에 의한 수신 방식으로 크게 나눌 수 있다. 끝으로 한국전자통신연구원에서 개발 중인 CMOS(Complementary Metal Oxide Semiconductor) 기술을 이용한 근거리 레이더 칩의 목표 성능, 구조, 설계 및 측정 결과에 대하여 소개하였다.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.3
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• pp.253-259
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• 2015

This paper introduces a signal processing technique for discrimination of missile target. In order to detect and discriminate the target, a seeker radar makes use of chirp waveform and stretch processing to generate high resolution range profiles(HRRPs). RELAX(relaxation) algorithm, which is one of the spectral estimation techniques, was used to find scattering centers of a missile from HRRP. From the information on the distribution of one-dimensional(1-D) scattering centers on a target, we can discriminate the target without noise.

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.310-315
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• 1999

We extracted narrow open water streams from JERS-1 SAR images of the Amazon rain forest. The extracted range of these streams were almost comparable to a high level extraction of the same streams from near-IR images of JERS-1 VNIR data notwithstanding that these features in SAR images show the strong dependence of the observation angle. Large water bodies are relatively easy to extract from JERS-1 SAR images, as they tend to appear as very dark areas; but streams whose width is nearly equal to or less than the spatial resolution no longer appear as very dark features. By using strong scatterers distributed sparsely along the radar facing sides of the streams, we can successfully estimate approximate ranges of waterways and then extract relatively dark line-like features within these ranges.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.2
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• pp.266-269
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• 2012

This paper introduces a signal processing technique for discrimination of ballistic missile's warhead. An interceptor missile to destroy the enemy's ballistic missile requires an information on the location of missile's warhead. In order to detect and locate the missile's warhead, a seeker radar in the interceptor missile makes use of chirp waveform to generate high resolution range profiles(HRRPs). We applied one of the well known spectral estimation technique called ESPRIT (Estimation of Signal Parameters by Rotational Invariance Technique) to these HRRPs to estimate scattering centers on the target. Using the information on the one-dimensional(1-D) scattering centers, we can find the location of the warhead by estimating the length of the missile, Simulation results show that the proposed signal processing technique is efficient in discriminating the warhead of an ballistic missile.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.1
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• pp.12-22
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• 2016

Convenience and safety are the key words for the automotive driving and various sensor technologies have been studied for enhanced perception of driving environments. In frequency modulated continuous wave (FMCW) radar systems, single antenna is enough for range and velocity detection of multiple targets. Multiple array antenna is needed for estimating direction of arrival(DoA). Using DoA estimation algorithm in time domain as in the conventional systems, it is difficult to distinguish vehicles lie in the same angle. In order to facilitate the enhanced angle estimation, DoA estimation algorithm is applied in frequency domain. In this paper, the method for applying multiple signal classification(MUSIC) algorithm in frequency domain is suggested and the performance is analyzed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.3
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• pp.456-463
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• 2021

In this paper, Ultra Wide-Band(UWB) radar sensor is employed to detect flying drones and avoid collision in dense clutter environments. UWB signal is preferred when high resolution range measurement is required for moving targets. However, the time varying motion of flying drones may increase clutter noises in return signals and deteriorates the target detection performance, which lead to the performance degradation of anti-collision radars. We adopt a dynamic clutter suppression algorithm to estimate the time-varying distances to the moving drones with enhanced accuracy. A modified Constant False Alarm Rate(CFAR) is developed using an adaptive filter algorithm to suppress clutter while the false detection performance is well maintained. For this purpose, a velocity dependent CFAR algorithm is implemented to eliminate the clutter noise against dynamic target motions. Experiments are performed against flying drones having arbitrary trajectories to verify the performance improvement.

• Journal of IKEEE
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• v.24 no.1
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• pp.339-346
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• 2020

In this paper, we propose an angle estimator that is designed to be applied to Bluetooth low-power application technology based on multiple signal classification (MUSIC) algorithm, and present the result of implementation in FPGA. The MUSIC algorithm is designed for H/W high-speed design because it requires a lot of calculations due to high accuracy, and the snapshot variable is designed to cope with various resolution requirements of indoor systems. As a result of the implementation with Xilinx zynq-7000, it was confirmed that 9,081 LUTs were implemented, and it was designed to operate at =the operating frequency of 100MHz.

• Korean Journal of Remote Sensing
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• v.31 no.4
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• pp.337-346
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• 2015

Water body extraction based on backscatter information is an essential process to analyze floodaffected areas from Synthetic Aperture Radar (SAR) image. Water body in SAR image tends to have low backscatter values due to homogeneous surface of water, while non-water body has higher backscatter values than water body. Non-water body, however, may also have low backscatter values in high resolution SAR image such as Kompsat-5 image, depending on surface characteristic of the ground. The objective of this paper is to present a method to increase backscatter contrast between water body and non-water body and also to remove efficiently misclassified pixels beyond true water body area. We create an entropy image using a Gray Level Co-occurrence Matrix (GLCM) and classify the entropy image into water body and non-water body pixels by thresholding of the entropy image. In order to reduce the effect of threshold value, we also propose Water Body Texture Index (WBTI), which measures simultaneously the occurrence of repeated water body pixel pair and the uniformity of water body in the binary entropy image. The proposed method produced high overall accuracy of 99.00% and Kappa coefficient of 90.38% in water body extraction using Kompsat-5 image. The accuracy analysis indicates that the proposed WBTI method is less affected by the choice of threshold value and successfully maintains high overall accuracy and Kappa coefficient in wide threshold range.