• Korean Journal of Computational Design and Engineering
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• v.9 no.3
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• pp.220-225
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• 2004

This paper presents a program for the automatic alignment of optical axes and evaluation of the optical filter performance which is a key technologies for the production of optical module. Recently the production of optical filter module mostly depends upon handwork or semi-automation. Moreover, they have used an expensive spectrum analyzer. In this work, we have developed an automatic alignment and evaluation program of optical filter module using photo detector and developed program for automation and cost reduction of the production of optical titter module.

• International Journal of Ocean System Engineering
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• v.1 no.2
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• pp.89-94
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• 2011

Underwater localization is a crucial capability for reliable operation of various types of underwater vehicles including submarines and underwater robots. However, sea water is almost impermeable to high-frequency electromagnetic waves, and thus absolute position fixes from Global Positioning System (GPS) are not available in the water. The use of acoustic telemetry systems such as Long Baseline (LBL) is a practical option for underwater localization. However, this telemetry network system needs to be pre-deployed and its availability cannot always be assumed. This study focuses on demonstrating the validity of terrain-based localization techniques in a GPS-denied underwater environment. Since terrain-based localization leads to a nonlinear estimation problem, nonlinear filtering methods are required to be employed. The extended Kalman filter (EKF) which is a widely used nonlinear filtering algorithm often shows limited performance under large initial uncertainty. The feasibility of using a particle filter is investigated, which can improve the performance and reliability of the terrain-based localization.

• Journal of electromagnetic engineering and science
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• v.7 no.3
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• pp.134-137
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• 2007

This paper presents the design of the compact UHF Bandpass filter of CT-type with a novel mixed coupling topology. In further detail, this new coupling structure mathematically equals the transmission zero that enables particularly the better rejection performance in the stopband without increasing the filter's order. To envision this design concept, we fabricated a microstrip filter whose measurement proves to agree with the predicted performance and the suggested coupling structure reduces the overall size, and will be possibly used in the miniaturized UHF apparatus such as the RFID system.

• Journal of information and communication convergence engineering
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• v.8 no.3
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• pp.267-272
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• 2010

For the last decade, recurrent neural networks (RNNs) have been commonly applied to communications channel equalization. The major problems of gradient-based learning techniques, employed to train recurrent neural networks are slow convergence rates and long training sequences. In high-speed communications system, short training symbols and fast convergence speed are essentially required. In this paper, the derivative-free Kalman filter, so called the unscented Kalman filter (UKF), for training a fully connected RNN is presented in a state-space formulation of the system. The main features of the proposed recurrent neural equalizer are fast convergence speed and good performance using relatively short training symbols without the derivative computation. Through experiments of nonlinear channel equalization, the performance of the RNN with a derivative-free Kalman filter is evaluated.

• Journal of Power Electronics
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• v.17 no.1
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• pp.190-199
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• 2017

In this paper, a predictive direct power control (DPC) method based on a Kalman filter is presented for three-phase pulse-width modulation (PWM) rectifiers to improve the performance of rectifiers with source voltages that are distorted with harmonic components. This method can eliminate the most significant harmonic components of the source voltage using a Kalman filter algorithm. In the process of predicting the future real and reactive power to select an optimal voltage vector in the predictive DPC, the proposed method utilizes source voltages filtered by a Kalman filter, which can mitigate the adverse effects of distorted source voltages on control performance. As a result, the quality of the source currents synthesized using the PWM rectifier is improved, and the total harmonic distortion (THD) values are reduced, even under distorted source voltages.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.309-311
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• 2005

In general, for specific applications, customized hardware showed better performance than general processor in terms of processing time and power consumption. However, customized hardware systems have lacks of flexibility in nature and it leads the difficulties for debugging and architecture level revision for performance enhancement. To solve this problem, reconfigurable hardware is developed. Proposed reconfigurable hardware architecture for FIR filter system can easily change the architecture of filter blocks including filter tap size and their signal path. Proposed FIR filter architecture was implemented on FPGA using several MUXs and registers and it showed the reconfigurablility and reusability in several examples.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.1
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• pp.158-164
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• 2008

In this paper, the performance of wet type filter for diesel engine combustion air has been studied with effects of air temperature, humidity, and pressure. After experiments are performed without diesel engine, it has been investigated the applicability to diesel engine. Wet type filter for diesel engine combustion air had advantages that it is not necessary to change air filter and that engine exhaust gas is environmentally friendly due to low NOx and particulate emission. Also, the filtration performance has been carried out with smoke shell.

• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.2232-2235
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• 2003

In speech communication systems where two different speech codecs are interoperated, transcoding algorithm is a good approach because of its low complexity and improved synthesized speech quality. This paper proposes an efficient method to further improve the performance of transcoding algorithms as well as to reduce the complexity. In the conventional transcoding algorithms. a post-filter and a perceptual weighting filter should be operated sequentially because both decoding and encoding processes are needed. This results in the redundancy of the processing in terms of complexity and perceptual quality. Using the fact that their filter structures are similar, we replaced the two filters with one. The proposed algorithm requires 72.8% lower complexity than the conventional transcoding algorithm when we compare only the complexity of the filtering processes. The results of both objective and subjective tests verify that the proposed algorithm has slightly better quality than the conventional one.

• Journal of Advanced Navigation Technology
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• v.11 no.2
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• pp.146-153
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• 2007

Autonomous unmanned vehicle is able to find the path and the way point by itself. For the more precise navigation performance, Extended kalman filter, which is integrated with inertial navigation system and global positioning system is proposed in this paper. Extended kalman filter's performance is evaluated by the simulation and applied to the unmanned vehicle. The test result shows the effectiveness of extended kalman filter for the navigation.

• Journal of Sensor Science and Technology
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• v.16 no.4
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• pp.294-300
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• 2007

Autonomous unmanned vehicle is able to find the path and the way point by itself. For the more precise navigation performance, Extended kalman filter, which is integrated with inertial navigation system and global positioning system is proposed in this paper. Extended kalman filter's performance is evaluated by the simulation and applied to the unmanned vehicle. The test result shows the effectiveness of extended kalman filter for the navigation.