• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.447-449
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• 1993

Digital filter is a signal processor which converts the sequence input sampled from analog signal into another sequence output. It includes software routines which filter digital signal, a computer system for executing the routines, and a data acquisition system which implements A/D, D/A signal conversion. In this paper, a data acquisition system is designed and implemented for one-board computer of MC68000. Also, the theory regarding signal conversion and and its problems occured in implementation are considered. And then, with the hardware implemented like this, design of a digital low-pass filter with the cutoff frequency of 200Hz is implemented, and related characteristics are considered.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.12
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• pp.665-672
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• 2000

This paper described the measurement technology to analyze the partial discharge characteristics for long term aging of insulations. This system was consisted of high voltage generation and measurement part, PD detection part, digital conversion and signal processing part. We used the VXI system for digital conversion and signal processing part. In the digital conversion part, we studied the error of partial discharge magnitude and memory capacity for reading digital signal with the sampling rate. In the signal processing part, we showed the program algorithm to count pulses and read peak values of partial discharge. The allowable minimum sampling rate of digizer was decided to 250kS/s through analyzing test. We confirmed that this system was very useful in the study of $\phi-q-n$ characteristics of long term PD experiments with specimens being consisted of internal void defects and CIGRE II electrodes.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.1
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• pp.44-49
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• 2002

In recent years, diagnostic techniques have been investigated to detect a partial discharge(PD) in a high voltage electrical equipment. Because PD signal is very sensitive and difficult to suppress strong noises such as narrow-band radio frequency noise and random noise, the accuracy and credibility of PD measurement might be influenced by surrounding interference. Using the technique of PD detection by electromagnetic wave, we have studied the characteristics of both PD and substation-in interference signal. Also, we propose a wavelet packet transform based technique to perform a feature extraction from the interference and PD signal and a classification of the extracted features. The results show that time-frequency characteristics between PD and interference can be obviously distinguished. It is helpful for the development of the insulation diagnosis technique.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.4
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• pp.819-830
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• 1999

NAVTEX system is an international automated direct-printing service, broadcast on 5181kHz and 490kHz, for the promulgation of navigational and meteorological warnings and urgent information to ships. With our government's adoption of the international convention for SAR(Search and Rescue) in 1993, various trials for the installation of NAVTEX system have been executed by the government committee, relating laboratory and experts. An important consideration of the installation for NAVTEX system is the availability that could broadcast messages written in korean letter. Also, the receiver which can process the signal demodulated from the two frequencies, 518kHz and 490kHz, should be developed and supplied in domestic. In this paper, the code table and algorithm for conversions between NAVTEX characters and Korean Letters are studied, and signal processing techniques of code conversion are developed. Circuit design and implementation of the NAVTEX simulator using the Direct Digital Synthesizer are discussed, code conversion algorithm and signal processing technique of the NAVTEX transmission are programmed in its circuits. For evaluating the its functional characteristics, receiving module which has I-Q channel structure is designed. From the measurements of simulator, the characteristics show the frequency stability of the $(\pm)2Hz$ and Spurious free dynamic range is -63dBc. And the simulator can generate simultaneously wanted signal and several interfere signals. So, its capability is valuable for designers of the transmitting system and NAVTEX receiver, for provider as testing facilities of the type approval.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.2
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• pp.35-40
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• 1997

The hysteresis control method has been frequently used for current control of power conversion equipments or motor drive systems. This method makes the measured signal follow the reference signal by changing the control signal whenever the error signal exceeds the preset band width. In this paper, hysteresis control method with fast response characteristics is applied for active noise control to suppress acoustic noise. Both Pentium processor and sound blaster 16 are used for experimental implementation, which executes A/D, D/A conversion and also is used as operating source of loudspeaker for audible noise cancellation.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1605-1614
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• 2013

This paper presents a probabilistic methodology for small signal stability analysis of power system with correlated wind sources. The approach considers not only the stochastic characteristics of wind speeds which are treated as random variables with Weibull distributions, while also the wind speed spatial correlations which are characterized by a correlation matrix. The approach based on the 2m+1 point estimate method and Cornish Fisher expansion, the orthogonal transformation technique is used to deal with the correlation of wind farms. A case study is carried out on IEEE New England system and the probabilistic indexes for eigenvalue analysis are computed from the statistical processing of the obtained results. The accuracy and efficiency of the proposed method are confirmed by comparing with the results of Monte Carlo simulation. The numerical results indicate that the proposed method can actually capture the probabilistic characteristics of mode properties of the power systems with correlated wind sources and the consideration of spatial correlation has influence on the probability of system small signal stability.

• Journal of Korea Multimedia Society
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• v.13 no.11
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• pp.1667-1676
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• 2010

In this paper, we propose a packet scheduling algorithm that assigns different number of HS-PDSCH(High Speed Primary Downlink Shared Channel) to the service user according to the received signal to interference ratio of CPICH(Common Pilot Channel) and to the traffic characteristics. Assigned channel number is determined by the signal to interference ratio level from CPICH. The highest signal to interference ratio user gets the number of channels based on the signal to interference ratio table and the remained channels are assigned to the other level users. Therefore the proposed scheme can provide the similar maximum service throughput and higher fairness than existing scheduling algorithm. Simulation results show that our algorithm can provide the similar maximum service throughput and higher fairness than MAX C/I algorithm and can also support the higher service throughput than proportional fairness scheme.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.7
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• pp.110-116
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• 1994

In this paper a Duty Effective Overlap Scanning method (DEOS) for the improvement of driving efficiency of LC displays which have the RMS voltage responding characteristics is proposed and new processing method of data signals for optimum application of this method is also proposed. Proposed method has a few advantages such as the increment of duty ratio the increment of driving power loaded on LC cell and the decrement of RMS voltage error rate caused by signal attenuation on electrodes composing of display when compared with the conventional method which is called as optimum voltage amplitude selection method. And also by adopting new data signal processing method which has 3 kinds of voltage levels additional advantage much improving crosstalk phenomenon which is the most serious problems of simple matrix structured display is obtained. For the characteristic estimation new mathematical representation for new overlap scanning method and data signal processing method are induced and defined. And by the defined formula and simulation the characteristics of the proposed method and the conventional method are compared and analyzed. As a result of estimation this new method being able to optimize the overlap rate of scan signal and using 3 levels of data signals has the characteristic which can improve the driving efficiency of LC displays.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4A
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• pp.316-323
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• 2002

In this paper, we propose a counter-countermeasure (CCM) in a crossed array tracker for efficient target tracking under countermeasures (CM) operated by a target. The proposed CCM adepts two detection bands and uses the signal distribution characteristics to discriminate between the target and the CMs. To avoid wrong detection of a target position due to missing signal pulses, it predicts current target position based on previous target position. To evaluate the performance of the proposed CCM in a crossed array tracker, we perform numerical simulations for target signal extraction and target tracking under various conditions. The simulation results show that the proposed CCM removes the CM effect well and tracks the target efficiently.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.395-400
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• 2013

In this paper, we introduce the implementation of high accurate level sensor system using the pulse wave type magnetostriction sensor. When a current pulse flows along the waveguide, the magnetic field also propagates towards the end of waveguide. When this magnetic field just passes the position of the magnet for level detection, the resultant magnetic field by these two magnetic fields makes a torsional reflected signal. This is used to calculate the time difference between a interrogation pulse wave and this torsional reflected signal. The key elements and characteristics were investigated to implement level sensor system based on this principle. We introduce a method to calculate the speed of ultrasonic reflected signal and how to make a model of sensing coil. In particular, we experiment with the characteristics of the torsional reflected signal according to the changes of the interrogation voltage and displacement. To make high accurate level sensor system, two methods were compared. One is to use the comparator and time counter, the other is STFT(Short Time FFT) which is capable of the time-frequency analysis.