• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.2
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• pp.94-103
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• 1997

The WCHF-FSJTC (wavelet circular harmonic function frequency selective joint transform correlator) using th wavelet transformed CHF as the reference image in FSJTC is proposed for rotation invariant pattern recognition. Since the wavelet transform has the property of feature extraction, the proposed system can have the better DC (discrimination cpability) and the higher SNR(signal to noise ratio) compared with the conventional CHF-CJTC(circular harmonic function conventional joint transform correlator). And since the structure of the proposed system is FSJTC which can eliminate auto-correlation and cross-correlation between input images, it can eliminate false alarm caused by the overlapping among correlation peaks. The used wavelet functio is the morlet function, which is proper for the reference image used in this paper. the optimal dialation parameter and oscillation frequency of the wavelet function are also achieved with varying the parameters of the wavelet function. The computer simulation shows that the proposed system has the best performance when the dilation parameter is 0.8 and the oscillation frequency is 0.48.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.36-42
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• 1998

In this study, active muffler was designed and was manufactured for exhaust noise reduction of commercial vehicle, then experiment of real vehicle was conducted. In a manufactured active muffler, because the flow of exhaust noise in tail pope outlet are become a plane wave, the global reduction if radiation noise from outlet and the placement of error microphone to avoid the exhaust gas of high temperature could be implemented. In control algorithm, reduction of noise of engine driving frequency and harmonic frequency can be archieved using proposed reference signal including a fixed speed state(2,000rpm, 3,000rpm, 4,000rpm) and a run-up speed state(2,000rpm$\rightarrow$4,000rpm) is accomplished with the active muffler installed in vehicle.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.3
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• pp.153-159
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• 2009

A CMOS frequency synthesizer for $5{\sim}6$ GHz UNII-band sub-harmonic direct-conversion receiver has been developed. For quadrature down-conversion with sub-harmonic mixing, octa-phase local oscillator (LO) signals are generated by an integer-N type phase-locked loop (PLL) frequency synthesizer. The complex timing issue of feedback divider of the PLL with large division ratio is solved by using multimodulus prescaler. Phase noise of the local oscillator signal is improved by employing the ring-type LC-tank oscillator and switching its tail current source. Implemented in a $0.18{\mu}m$ CMOS technology, the phase noise of the LO signal is lower than -80 dBc/Hz and -113 dBc/Hz at 100 kHz and 1MHz offset, respect-tively. The measured reference spur is lower than -70 dBc and the power consumption is 40 m W from a 1.8 V supply voltage.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.11
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• pp.1606-1610
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• 2012

Hysteresis current regulator has been used widely because of its simple principle and structure. However, when the current band width is too narrow or the applied voltage is relatively too high, the switching frequency may increase abruptly and it generates a large amount of heat. Thus, this study will suggest a better and simple method to reduce the switching frequency. For single phase current control, the proposed hysteresis current control is executed by adding 0 mode state and comparing the slope of the current reference. This simple method decreases the generated switching frequency and significantly reduces the generated heat. This proposed method was proved with simulations and experiments comparing with the classical hysteresis current control method.

• Journal of Power Electronics
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• v.16 no.1
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• pp.18-26
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• 2016

This paper proposes a compensation algorithm for reducing a specific ripple component on synchronous reference frame phase locked loop (SRF-PLL) in grid-tied single-phase inverters. In general, SRF-PLL, which is based on all-pass filter to generate virtual voltage, is widely used to estimate the grid phase angle in a single-phase system. In reality, the estimated grid phase angle might be distorted because the phase difference between actual and virtual voltages is not 90 degrees. That is, the phase error is caused by the difference between cut-off frequency of all-pass filter and grid frequency under grid frequency variation. Therefore, the effects on phase angle and output current attributed to the phase error are mathematically analyzed in this paper. In addition, the proportional resonant (PR) controller is adapted to reduce the effects of phase error. The validity of the proposed algorithm is verified through several simulations and experiments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.263-268
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• 2000

In this paper, a new indirect feedback active noise control (ANC) scheme based on the fundamental frequency estimation is proposed for systems with a harmonic noise. When reference signals necessary for feedforward ANC configuration is difficult to obtain, the conventional ANC algorithms for multi-tonal noise do not measure the reference signals but generate them with the estimated frequencies. However, the beating phenomena, in which certain frequency components of the noise vanish intermittently, may make the adaptive frequency estimation difficult. The confusion in the estimated frequencies due to the beating phenomena makes the generated reference signals worthless. The proposed algorithm consists of two parts. The first part is a reference generator using the fundamental frequency estimation and the second one is the conventional feedforward control. We propose the fundamental frequency estimation algorithm using decision rules, which is insensitive to the beating phenomena. In addition, the proposed fundamental frequency estimation algorithm has good tracking capability and lower variance of frequency estimation error than that of the conventional cascade ANF method. We are also able to control all interested modes of the noise, even which cannot be estimated by the conventional frequency estimation method because of the poor SIN ratio. We verify the performance of the proposed ANC method through simulations for the measured cabin noise of a passenger ship and the measured time-varying engine booming noise of a passenger vehicle.

• Journal of Biomedical Engineering Research
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• v.32 no.2
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• pp.134-143
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• 2011

The selection of meaningful clinical tests and its reference values from a high-dimensional clinical data with imbalanced class distribution, one class is represented by a large number of examples while the other is represented by only a few, is an important issue for differential diagnosis between similar diseases, but difficult. For this purpose, this study introduces methods based on the concepts of both discernibility matrix and function in rough set theory (RST) with two discretization approaches, equal width and frequency discretization. Here these discretization approaches are used to define the reference values for clinical tests, and the discernibility matrix and function are used to extract a subset of significant clinical tests from the translated nominal attribute values. To show its applicability in the differential diagnosis problem, we have applied it to extract the significant clinical tests and its reference values between normal (N = 351) and abnormal group (N = 101) with either cholecystitis or cholelithiasis disease. In addition, we investigated not only the selected significant clinical tests and the variations of its reference values, but also the average predictive accuracies on four evaluation criteria, i.e., accuracy, sensitivity, specificity, and geometric mean, during l0-fold cross validation. From the experimental results, we confirmed that two discretization approaches based rough set approximation methods with relative frequency give better results than those with absolute frequency, in the evaluation criteria (i.e., average geometric mean). Thus it shows that the prediction model using relative frequency can be used effectively in classification and prediction problems of the clinical data with imbalanced class distribution.

• Transactions on Semiconductor Engineering
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• v.2 no.3
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• pp.1-5
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• 2024

This paper presents a crystal-less reference clock recovery (CR) frequency synthesizer with compensation designed for Bluetooth Low Energy (BLE) Smart-tag applications, operating at frequencies of 32, 72, and 80MHz. In contrast to conventional frequency synthesizers, the proposed design eliminates the need for external components. Using a single-ended antenna to receive a minimal input power of -36dBm at a 2.4GHz signal, the CR synthesizes frequencies by processing the RF signal received through a Low Noise Amplifier ( L N A ) . This approach allows the system to generate a reference clock without relying on a crystal. The received signal is amplified by the LNA and then input to a 16-bit ACC (Automatic Clock Compensation) circuit. The ACC compares the frequency of the received signal with the oscillator output signal, using the synthesis of a 32MHz reference clock through a frequency compensation method. The oscillator is constructed using a Ring Oscillator (RO) with a Frequency Divider, offering three different frequencies (32/72/80MHz) for various system components. The proposed frequency synthesizer is implemented using a 55-nm CMOS process.

• Journal of Wind Energy
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• v.13 no.3
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• pp.13-21
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• 2022

When a wind turbine is designed, the dynamic stability of the system as well as the dynamic characteristics of the main components such as blades, hub, main shaft and tower must be evaluated. In particular, the natural frequencies of a blade, as a main load-generating component, need to be measured and assessed by component level testing. In conventional practice, the natural frequencies of a blade are determined as the measured frequencies near the reference frequencies provided by FE analysis results. But the reference frequencies are also uncertain since designers have difficulty distinguishing the torsional mode shape among the analysis results due to the complexity of its mode shape. So, in conventional practice, the determination of a measured torsional frequency inevitably contains uncertainty. Therefore, a novel method to definitely determine the torsional frequencies from the experimental data itself is necessary. In this paper, a new methodology to measure the torsional frequency of a blade was studied from the perspective of a modal test procedure, data processing method and mode determination logic. Finally, the validity of the method that can measure torsional frequency without reference FE analysis results was verified by applying it to an actual large wind turbine blade

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.10
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• pp.1774-1779
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• 2016

This paper proposes a portable cable fault detection system with automatic fault distinction and distance measurement using time-frequency correlation and reference signal elimination method and automatic fault classification algorithm in order to have more accurate fault determination and location detection than conventional time domain refelectometry (TDR) system despite increased signal attenuation due to the long distance to cable fault location. The performance of the developed system method was validated via an experiment in the test field constructed for the standardized performance test of power cable fault location equipments. The performance evaluation showed that accuracy of the developed system is less than 1.34%. Also, an error of automatic fault type and location by detection of phase and peak value through elimination of the reference signal and normalization of correlation coefficient and automatic fault classification algorithm not occurred.