• Journal of the Korea Institute of Military Science and Technology
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• v.3 no.1
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• pp.58-65
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• 2000

A target signal simulation method for passive sonar systems is introduced. The method uses multirate signal processing techniques to simulate moving target signals in the multi-path sound propagation environment by introducing Lloyd's mirror and Doppler effect. Time and frequency variation of target signal due to the target maneuvering is also considered to provide realistic ship signatures in the LOFAR gram so that the simulated target is used for sonar operator training. Synthesized target characteristics is analyzed and compared with real target signal in terms of interference pattern and frequency variation in the LOFAR gram.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.3
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• pp.16-24
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• 2007

The high-frequency analysis method of back-scattering cross section spectrum of rotating targets is established. The time history of the back-scattering cross section is calculated using a quasi-stationary approach, based on a physical optics and a physical theory of diffraction, combining an adaptive triangular beam method to consider the shadow effect. And the spectra of back-scattering cross section by the Doppler effect are analyzed applying a simple fast Fourier transform method to its time history. The numerical calculation for rotating targets, such as rotating metal plates and underwater propeller, are carried out. The time history appears to be periodic with respect to the number of wings. The backscattering cross section spectrum level and its frequency shift are dependent on the rotating speed, direction, and the shape of the targets.

• Bulletin of the Korean Space Science Society
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• 2002.05b
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• pp.17.1-17
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• 2002

• The Journal of the Acoustical Society of Korea
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• v.35 no.2
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• pp.125-133
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• 2016

In order to obtain high-resolution seafloor images, research on SA (Synthetic Aperture) processing and the development of related underwater systems have been performed in many countries. Recently the SA processing is also recognized as an important technique in Korea and researchers started related basic study. However, most previous studies ignored the Doppler effect by a moving receiver array. In this paper reconstructed SAS (Synthetic Aperture Sonar) images and position errors are analyzed according to the speed of a moving array for understanding its moving effect on the SAS images. In the analysis the spatial frequency domain interpolation algorithm is used. The results show that as the moving speed of the array increases the estimated position error also increases and image distortion gets worse when we do not consider the array motion. However, if the compensated receiver signals considering the array motion are used the position error and image distortion can be eliminated. In conclusion a signal processing scheme which compensates the Doppler effect is necessary especially in the condition where the array speed is over 1 m/s.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5841-5846
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• 2013

In this work, we consider the effect of doppler bandwidth on the performance of channel sounding. We develop the mathematical formulation of the problem and compare the MMSE channel estimator to the simple correlator. Examples of the performance of the MMSE and correlator estimators are presented for the single-input single-output (SISO) case with various values of Doppler bandwidth to assess the impact of time variation. The results show that as the $f_dT$ product increases the performance of both the MMSE and correlator estimates gets worse, and that the performance of the MMSE estimator improves relative to the correlator.We also consider case that the exact statistics of the channel are unknown It is shown that when the mismatch is not too large, the MMSE estimator with mismatch still does better than the simple correlator, but if the mismatch is large, then the correlator can do better.

• Journal of IKEEE
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• v.27 no.3
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• pp.265-272
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• 2023

In this paper, a GPU-accelerated kernel of range Doppler algorithm (RDA) was developed for real-time image formation based on frequency modulated continuous wave (FMCW) synthetic aperture radar (SAR). A pinned memory was used to minimize the data transfer time between the host and the GPU device, and the kernel was configured to perform all RDA operations on the GPU to minimize the number of data transfers. The dataset was obtained through the FMCW drone SAR experiment, and the GPU acceleration effect was measured in an intel i7-9700K CPU, 32GB RAM, and Nvidia RTX 3090 GPU environment. Including the data transfer time between host and devices, it was measured to be accelerated up to 3.41 times compared to the CPU, and when only the acceleration effect of operation was measured without including the data transfer time, it was confirmed that it could be accelerated up to 156 times.

• Korea Science and Art Forum
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• v.30
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• pp.367-376
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• 2017

This study introduces conducting practice tool for conducting majoring students. There have been various types of related research, but most of them have not been optimized for the conducting major. In addition, we thought that it would be a tool to be able to carry like a musical instrument in order to practice conducting without restriction of place and time. And also, it will be one of the few tools to focus on queuing. The practice tool presented in this study use the Doppler effect to overcome the limitations of previous studies. It was concluded that the Doppler method, which is highly compatible, simple, and accurate, is superior to motion detection methods using existing sensors. It is expected that it will be used not only as a conducting but also as an interaction tool of various media.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.1
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• pp.71-82
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• 1996

In this paper, the Doppler phase error due to the relative velocity between a satellite and the earth station in communications using a low earth orbit mobile satellite is detected. The performance of BPSK system in the presence of Rician fading with Doppler phase error and interference, noise is compared with that of the system disturbed by Doppler phase error and noise only. The expression of error rate performance of BPSK system is derived as the type of complementary error function. The numerical calculation of the induced equation are performed in terms of satellite-height, orbit-eccentricity, the velocity of the earth, Rician fading parameter, signal to interference rateio (SIR), the ratio of carrier frequency and base band bit rate. The main conclusion that can be drawn from this analysis is that Rician fading channel environment with Doppler phase error and interference effect yields severe performance degradation than Do- ppler phase error and noise effect in satellite communication channel. And using the numerical calculation, we give a quantitative insight how much the satellite communication channel parameters degrade the system performance. Furthermore it is shown that an appropriate transmission power control for the performance enhancement is beneficial to the new satellite communication system planning.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.2
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• pp.128-138
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• 1996

In this paper, the Doppler phase error due to the relative velocity between a satellite and the earth station in communications using a low earth orbit mobile satellite is detected. The performance of BPSK system in the presence of Rician fading channel environment with Doppler phase error, inter- ference and noise is compared with that of the system disturbed by Doppler phase error and noise only, And adopted coding techniques are Hamming, BCH, RS and convolution codes. The expression of error rate performance of BPSK system is derived as the type of complementary error function. The main conclusion that can be drawn from this analysis is that Rician fading channel environment with Do- ppler phase error and interference, noise effect yields severe performance degradation then Doppler phase error and noise effect in satellite communication channel. The conclusion can be drawn from this analysis is that using coding technique then noncoding. And using the numerical calculation, we give a quantitative insight how much the satellite communication channel parameters degrade the system per- formance. Furthermore it is shown that an appropriate transmission power control for the performance enhancement is beneficial to the new satellite communication system planning.

• Korean Journal of Remote Sensing
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• v.21 no.2
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• pp.163-171
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• 2005

I have developed a processor for synthetic aperture radar (SAR) raw data compression using range-doppler algorithm for educational purpose. The program realized a generic SAR focusing algorithm so that it can deal with any SAR system if the specification is known. It can run efficiently on a low-cost computer by selecting minimum size out of a whole dataset, and can produce intermediate images during the process. Especially, the program is designed for educational purpose in such a way that Doppler centroid and azimuth ambiguity can be determined graphically by the user. By distributing the source code and the algorithm to public, I intend to maximize the educational effect on understanding and utilizing SAR data. This paper introduces the principle of SAR focusing algorithm embedded on the eSAR processor and shows an example of data processing using ERS-1 raw data.