• The Journal of the Acoustical Society of Korea
• /
• v.35 no.4
• /
• pp.310-318
• /
• 2016

This study deals with a method to localize a noise source occuring in a marine vehicle in a 3D environment. Even when access to the noise source is limited for a marine vehicle, such as a ship or a submarine in operation, the signal received on a hydrophone located elsewhere contains Doppler effected noise by moving relatively. This study suggests noise localization algorithm in 3D based on Doppler effect by moving marine vehicle. Using a known source mounted on the vehicle, the noise source was estimated by reducing the range of Doppler center and closest point of approach via the least square method. The algorithm was verified through various simulations and it was shown that the noise could be localized in 3D based on Doppler effect by employing two fixed hydrophones located at the vehicle's exterior points and a known reference signal generator located somewhere on the vehicle.

• Proceedings of the KIEE Conference
• /
• 1987.11a
• /
• pp.392-397
• /
• 1987

This paper concerns a method for micro-wave imaging. The image reconstruction of a perfect conducting cylinder by phase and amplitude measurement using the X-Band multifrequency is presented troll the simulated data. The high degree of range resolution is achieved using large signal band-width and cross-range resolution is obtained by doppler processing. The comparison of image reconstruction between range doppler processing and circular convolution algorithm is also shown.

• The Journal of the Acoustical Society of Korea
• /
• v.38 no.3
• /
• pp.302-307
• /
• 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 Electromagnetic Engineering and Science
• /
• v.20 no.8
• /
• pp.784-790
• /
• 2009

A forward-looking automotive radar typically utilizes the frequency modulated continuous wave(FMCW) or pulsed-Doppler waveform for the Information acquisition of the target range and velocity. In order to obtain the high resolution target information, however, a narrow pulse width and wide bandwidth are inherently required, thus resulting in high peak power and high speed digital converter processing. In this paper, a stepped-frequency pulsed-Doppler(SFPD) waveform algorithm is proposed for high resolution forward looking automotive radar application. The performance of the proposed SFPD waveform technique is analyzed and compared with the conventional FMCW and PD method. Since this technique can be used for the high resolution target imaging with arbitrary range and Doppler resolution, it is expected to be useful In automotive radar target classification for the precision collision avoidance applications in the future.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.06a
• /
• pp.145-150
• /
• 2007

We briefly introduce the theory of GB-SAR focusing and interferometry. Deramp-FFT algorithm is evaluated as a far-range, partial focusing method along with its limitations in the near-range application. Various interferometric configurations with temporal, spatial, and/or frequency baselines are also discussed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.25 no.2
• /
• pp.255-258
• /
• 2014

Imaging in bistatic radar has been known a more difficult task than that in monostatic radar. It is because the behavior of the bistatic range and the bistatic Doppler due to the motion of a transmitter and a receiver is so random that the compensation procedure, which we call an imaging algorithm, is quite complicated. This paper presents a bistatic radar imaging algorithm that can be used in some specific bistatic radar geometry. We show this geometry can present rectangular-like resolution cell on isorange-isoDoppler contours map. We also present the associated resolution and simulation results.

• The Journal of the Acoustical Society of Korea
• /
• v.37 no.6
• /
• pp.489-498
• /
• 2018

In this paper, a target detection method based on beamspace-domain multichannel nonnegative matrix factorization is studied when an echo of continuous-wave ping is received from a low-Doppler target in reverberant environment. If the receiver of the continuous-wave active sonar moves, the frequency range of the reverberation is broadened due to the Doppler effect, so the low-Doppler target echo is interfered by the reverberation in this case. The developed algorithm analyzes the multichannel spectrogram of the received signal into frequency bases, time bases, and beamformer gains using the beamspace-domain multichannel nonnnegative matrix factorization, then the algorithm estimates the frequency, time, and bearing of target echo by choosing a proper basis. To analyze the performance of the developed algorithm, simulations were performed in various signal-to-reverberation conditions. The results show that the proposed algorithm can estimate the frequency, time, and bearing, but the performance was degraded in the low signal-to-reverberation condition. It is expected that modifying the selection algorithm of the target echo basis can enhance the performance according to the simulation results.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.7 no.5
• /
• pp.1166-1179
• /
• 2013

In wireless sensor network (WSN) environments, environmental noises are generated by, for example, small passing animals, crickets chirping or foliage blowing and will interfere target detection if the noises are higher than the sensor threshold value. For accurate tracking by acoustic WSNs, these environmental noises should be filtered out before initiating track. This paper presents the effect of environmental noises on target tracking and proposes a new algorithm for the noise mitigation in acoustic WSNs. We find that our noise mitigation algorithm works well even for targets with sensing range shorter than the sensor separation as well as with longer sensing ranges. It is also found that noise duration at each sensor affects the performance of the algorithm. A detection algorithm is also presented to account for the Doppler effect which is an important consideration for tracking higher-speed ground targets. For tracking, we use the weighted sensor position centroid to represent the target position measurement and use the Kalman filter (KF) for tracking.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.9
• /
• pp.906-913
• /
• 2004

FFT algorithm is the most popular ISAR imaging technique from radar data. It requires polar formatting technique to make a focused image of the target as MTRC(Moving Through Resolution Cell) causes a blurred image when the data is from the wide azimuth angle. But there exits the angle limit for the application of the polar formatting and we cannot obtain clear images if the range of the azimuth angle is too wide to process with polar, formatting. This paper analyses the relative merits of the polar formatting algorithm accompanied by interpolation to the CDT algorithm that needs not the interpolation.

• Proceedings of the KIEE Conference
• /
• 1997.07b
• /
• pp.459-461
• /
• 1997

This paper describes a simulation method of the correlation-signal output, which has Doppler effect (variation of amplitude, phase, and frequency) caused by the moving-effect of target and encounter conditions. Using these results, we can develope and verify the algorithm of the signal processing parts of the code correlation range sensor with ease.