• The Journal of the Acoustical Society of Korea
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• v.35 no.5
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• pp.331-339
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• 2016

This paper suggests an estimation method of the source signal and the channel impulse response (CIR) using ray-based blind deconvolution (RBD) in the underwater acoustic channel environment where Doppler effect exists by the relative motion between source and receiver. It is difficult to estimate the CIR on Doppler effect by the matched filter with a highly Doppler-sensitive waveform such as the m-sequence signal because Doppler shift can severely degrade the correlation between the received signal corrupted by Doppler effect and the original source signal. In this study, the Doppler-shifted source-signal's phase is estimated using the RBD, and the received signal is compensated by it to obtain the Doppler-corrected CIR. It is verified that using the matched filter with the received signal from the experimental data fails to estimate the CIR while the obtained CIR by the suggested method has the similarity to the propagation path of the ray model. Also, the results show that the reconstructed source signal using the RBD has the better Doppler shift compensation than the Doppler-shifted source signal derived from scattering function.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1205-1211
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• 2004

We propose a train position estimation method for automatic train control system. The accurate train position should be continuously feedback to control system for safe and efficient operation of trains in railway. In this paper, we propose the sensor fusion method integrating the tachometer, the transponder, and the doppler sensor for estimation of train position. The external sensors(transponder, doppler sensor) are used to compensate for the error of internal sensor(tachometer). The Kalman filter is also applied to reduce the measurement error of the sensors. Simulation results are then presented to verify the usefulness of the proposed method.

• Journal of electromagnetic engineering and science
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• v.10 no.4
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• pp.250-255
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• 2010

This paper presents a non-contact measurement method of vital signal by the use of multiple-input multiple-output (MIMO) bio-radar system, configured with two antennas that are separated by a certain distance. The direction of arrival (DOA) estimation algorithm for coherent sources was applied to detect vital signals coming from different spatial angles. The proposed MIMO bio-radar system was composed of two identical transceivers sharing single VCO with a PLL. In order to verify the performance of the system, the DOA estimation experiment was completed with respect to the human target at angles varying between $-50^{\circ}$ and $50^{\circ}$ where the bio-radar system was placed at distances (corresponding to 50 cm and 95 cm) in front of a human target. The proposed MIMO bio-radar system can successfully find the direction of a human target.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.1861-1868
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• 2014

In wireless communication systems, a frequency offset exist at the received signal due to the transmitter-receiver oscillator mismatch and Doppler effect in mobile environments. Those offsets rotate the received signal's phase and degrade the receiver performance. Hence, estimation and compensation of the frequency offset is crucial at the receiver. This paper proposes a new frequency offset estimation technique based on partial correlation. The proposed method requires less computational complexity than that of the conventional method. In addition, since the proposed one can estimate a wide range of frequency offset without estimation accuracy loss, the application of the method is desirable for the communication environments that have a large frequency offset. In order to verify the performance of our proposed scheme, a series of computer simulations have been carried out and compared against those of the conventional method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.9
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• pp.1753-1759
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• 2009

A weather radar as one of the remote sensing devices to analyze the weather phenomena receives the return echoes which consist of scattered electromagnetic wave signals from rain, cloud and dust particles, etc. These received Doppler weather spectra are analyzed to extract the various characteristic weather information. The mean wind velocity is one of the important weather parameters which can be obtained by a weather radar ed it may be useful in the prevention of weather hazards occurred by the abrupt shift of wind in small geographical scales such as microbursts. It is usually estimated by pulse pair method which is considered to be reliable and very efficient in the computational requirement. However, there are some problems in the accurate estimation of the mean velocity if Doppler spectra of weather signals appear to be asymmetric gaussian or multi-peak spectra. Therefore, in this paper, the problems in the mean estimation of asymmetric Doppler spectra are analyzed and the improved method is suggested.

• The Journal of the Acoustical Society of Korea
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• v.38 no.3
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• pp.302-307
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• 2019

In modern Anti-Submarine Warfare, there are various ways to locate a submarine in a two-dimensional space. For more effective tracking and attack against a submarine the depth of the target is a critical factor. However, it has been difficult to find out the depth of a submarine until now. In this paper a possible solution to the depth estimation of submarines is proposed utilizing DIFAR (Directional Frequency Analysis and Recording) sonobuoy information such as contact bearings at or prior to CPA (Closest Point of Approach) and the target's Doppler signals. The relative depth of the target is determined by applying the Pythagorean theorem to the slant range and horizontal range between the target and the hydrophone of a DIFAR sonobuoy. The slant range is calculated using the Doppler shift and the target's velocity. the horizontal range can be obtained by applying a simple trigonometric function for two consecutive contact bearings and the travel distance of the target. The simulation results show that the algorithm is subject to an elevation angle, which is determined by the relative depth and horizontal distance between the sonobuoy and target, and that a precise measurement of the Doppler shift is crucial.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12B
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• pp.1244-1250
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• 2010

This paper presents a detection and ranging algorithm for a high-speed targets in the high PRF radar. We show, unlike the conventional methods, it firstly estimates Doppler frequency with a quasi-periodic pulse train prior to range processing. The estimated Doppler frequency can compensate the phase error enbeded in the received signal, which makes the signal integrated coherently in the range direction and localizes the target's signiture in low SNR. We present the derivation of the proposed algorithm and discuss how the system parameters such as the range/Doppler sampling condition, processing time and Doppler estimation error affect the performance of the proposed algorithm, which is verified by simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5C
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• pp.317-325
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• 2011

For OFDM (Orthogonal Frequency Division Multiplexing) systems, 2-D MMSE (2-Dimensional Minimum Mean Square Error) channel estimation provides optimal performance in frequency/time selective fading channel environment. However, the 2-D MMSE channel estimation has high computational complexity due to the large matrix size, because the 2-D MMSE channel estimation considers time as well as frequency axis for channel estimation. To reduce the computational complexity, we propose a modified 2-D MMSE channel estimator which is based on 1-D MMSE channel estimation with weighted sum. Furthermore, we consider RMS delay spread and Doppler frequency estimation for 2-D MMSE channel estimation. We show that the proposed method can significantly reduce computational complexity as well as that it can perform close to 2-D MMSE channel estimation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.8
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• pp.437-444
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• 2014

In this paper, we propose a path loss model with the multiple antennas and doppler shift for high speed railroad communication. Path loss model is very important in order to design consider diverse characteristic in high-speed train communication. Currently wireless communication systems use the multiple antennas in order to improve the channel capacity or diversity gain. However, until recently, many researches on path loss model only consider geographical environment between the transmitter and the receiver. There is no study about path loss model considering diversity effect and doppler shift. In order to make average residuals considering doppler shift we use tuned free space path loss model which is utilized for measurement results at high speed railroad. The environment of high speed rail is mostly at viaduct and flatland over than 50 percent. And in order to make average residuals considering multiple antenna we use theoretical estimation of diversity gain with MRC scheme. proposed model predict loss of received signal by estimating average residuals between diversity effect and doppler shift.

• Korean Journal of Remote Sensing
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• v.19 no.6
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• pp.421-430
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• 2003

The extraction technique for Doppler information(Doppler centroid frequency(f$_{dc}$) and it's rate(f$_{r}$) is very important to make an image from the radar echo signal data. Clutterlock and auto-focusing techniques have been widely used to extract accurate Doppler information. But both techniques are not easy to implement in SAR processor and need quite lots of time to calculate accurate f$_{dc}$ and f$_{r}$ because they are generally based on echo signal data only. In this paper we suggest hybrid method for Doppler extraction using both of echo signal data and orbital and attitude information of satellite. In this method CDE(Correlation Doppler Estimation) technique is only used to estimate exact modular f$_{dc}$ using received echo signal data and rest of other algorithms are based on simple mathematical model of geometry between satellite and ground targets as well as the Doppler frequency ambiguity resolving problem. The experimental results using Radarsat-1 signal data shows that the proposed method can be effectively used for the extraction of Doppler information.