• Journal of the Ergonomics Society of Korea
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• v.27 no.4
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• pp.95-101
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• 2008

This research is to develop PPG filtering method for respiration measurement in U-Health Care system. Respiration rate was determined by filtering PPG and analyzing its spectrum. Optimal filter of PPG has been selected to get respiration by testing 120 sets of experiment data using 700 filtering cases. As a result, 2nd order Bessel-filter that used band-pass cutoff frequency at 0.175~0.4Hz with second order was good at developing respiration signal. Respiration signal in time domain could be continuously analyzed by converting frequency domain using spectrum analysis. 24 seconds has been found to be optimal time duration of collecting PPG data for determining respiration. Therefore, this study was successful of getting not only heart activity but also respiration by only PPG. Minimal invasive measurement obtaining multi-bio information by one sensor can be expected to apply to U-Health Care and human computer interaction.

• Proceedings of the Technology Innovation Conference
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• 2003.02a
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• pp.63-77
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• 2003

In this paper, we investigate the co-movements of the real GDP cycle and the telecommunications service expenditure cycle over 1980 through 2000 in Korea. We used several appropriate statistical tools to characterize and to compare the co-movements between the two aforementioned variables. The statistics presented in this paper are common, easy to Interpret and capture important visual, descriptive information and the dynamics of data that would be lost if one focused only on the unconditional correlation coefficients of de-trended data. This paper examines four possible characteristics for the co-movements of real GDP and telecommunications service expenditure in Korea. The first is that in low frequency, the cyclical movements in telecommunications service expenditure are very similar to the cyclical movements in real GDP, The second is that in the high frequency, the estimated stationary cyclical telecommunications service expenditure is not closely related to the estimated stationary cyclical real GDP. Third, according to co-spectra analysis, the strong relationships between the variables are found in the mid-term frequency and as such this empirical finding has important implications for telecommunications policy and telecommunications service implementation strategies. Finally, in the short-term period, our empirical results support telecommunications network theories such as path dependence properties, lock-in, positive feedback externality, and network externality.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5C
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• pp.520-529
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• 2007

In this paper, we study the characteristics of parameters which are related to performance of MCTF which is a key technique for wavelet-based scalable video coding, and propose an improved MCTF method. The proposed MCTF method adopts the motion estimation of which motion vector field is distributed more uniformly using variable block sizes. By using the proposed method, the decomposition performance of temporal filter is improved, and the energy in high-frequency frames is reduced. It can help the entropy coder to generate lower bitrate. From simulation results, we verify the decomposed energy on high-frequency frame using the proposed method is reduced by 25.86% at the most in terms of variance of the high-frequency frame.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.547-550
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• 2001

Through matched filtering synthetic aperture radar (SAR) produces high-resolution imagery from data collected by a relative small antenna. While the impulse response obtained by the matched filter approach produces the best achievable signal-to-noise ratio, large sidelobes must be reduced to obtain higher-resolution SAR images. So, many enhancement methods of SAR imagery have been proposed. As a deconvolution method, the phase-extension inverse filtering is based on the characteristics of the matched filtering used in SAR imaging. It improves spatial resolution as well as effectively suppresses the sidelobes with low computational complexity. In the phase-extension inverse filtering, the impulse response is obtained from simulation with a point target. But in a real SAR environment, for example ERS-1, the impulse response is distorted by many non-ideal factors. So, in the phase-extension inverse filtering for a real SAR processing, the magnitudes of the frequency transfer function have to be compensated to produce more desirable results. In this paper, an estimation method to obtain a more accurate impulse response from a real SAR image is studied. And a compensation scheme to produce better performance of the phase-extension inverse filtering is also introduced.

• The Journal of the Acoustical Society of Korea
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• v.41 no.2
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• pp.192-198
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• 2022

As an effective weapon system for anti-submarine warfare, DIrectional Frequency Analysis and Recording (DIFAR) sonobuoy detects underwater targets via beamforming with three channels composed of an omni-direcitonal and two directional channels. However, ambient noise degrades the detection performance of DIFAR sonobouy in specific direction (0°, 90°, 180°, 270°). Thus, an ambient noise redcution technique is proposed for performance improvement of acoustic target detection of DIFAR sonobuoy. The proposed method is based on OTA (Order Truncate Average), which is widely used in sonar signal processing area, for ambient noise estimation and Wiener filtering, which is widely used in speech signal processing area, for noise reduction. For evaluation, we compare mean square errors of target bearing estmation results of conventional and proposed methods and we confirmed that the proposed method is effective under 0 dB signal-to-noise ratio.

• ETRI Journal
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• v.43 no.6
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• pp.966-977
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• 2021

Filterbank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) is an attractive alternative to the orthogonal frequency division multiplexing (OFDM) modulation technique. In comparison with OFDM, the FBMC-OQAM signal has better spectral confinement and higher spectral efficiency and tolerance to synchronization errors, primarily due to per-subcarrier filtering using a frequency-time localized prototype filter. However, the filtering process introduces intrinsic interference among the symbols and complicates channel estimation (CE). An efficient way to improve the CE in FBMC-OQAM is using a technique known as windowed frequency domain averaging (FDA); however, it requires a priori knowledge of the window length parameter which is set based on the channel's frequency selectivity (FS). As the channel's FS is not fixed and not a priori known, we propose a k-nearest neighbor-based machine learning algorithm to classify the FS and decide on the FDA's window length. A comparative theoretical analysis of the mean-squared error (MSE) is performed to prove the proposed CE scheme's effectiveness, validated through extensive simulations. The adaptive CE scheme is shown to yield a reduction in CE-MSE and improved bit error rates compared with the popular preamble-based CE schemes for FBMC-OQAM, without a priori knowledge of channel's frequency selectivity.

• Journal of IKEEE
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• v.12 no.4
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• pp.234-238
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• 2008

We demonstrate a simple method to generate a stable 40 GHz pulse train at 1550 nm by spectral filtering of a 10 GHz mode.locked pulse source using a fiber Fabry-Perot interferometer (FFPI). A high finesse FFPI with a 40 GHz free spectral range blocks successfully unwanted spectral components of a 10 GHz pulse source and passes only 40 GHz spaced spectral lines ensuring pulse repetition-frequency quadruplication of the input pulses.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.609-611
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• 1996

Zero-Cross Detector makes pilot signal to control the power to CEDM(Control Element Drive Mechanism). Existing Zero-Cross Detectors has had a problem which can cause unexpected reactor trip resulted from fluctuating frequency of input signal coming from M/G Set. The existing Zero-Cross Detector can't work properly when power frequency is varying because it was designed to work under stable M/G Set operation, and produces wrong pilot signal and output voltage. In this report the Zero-Cross Detector is improved to resolve voltage fluctuating problem by using new devices such as digital noise filtering circuit, variable cycle compensator and alarm circuit. And through the performance verification it shows that new circuit is better than old one. If suggested detector is applied to plant, it is possible to use it under House Load Operation because stable voltage can be generated by new Zero-Cross Detector.

• Journal of Multimedia Information System
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• v.4 no.2
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• pp.65-73
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• 2017

This paper proposes a method to improve the image quality by designing Unsharp Mask Filter (UMF) based on Retinex theory which controls the frequency pass characteristics adaptively. Conventional unsharp masking technique uses blurring image to emphasize sharpness of image. Unsharp Masking(UM) adjusts the original image and sigma to obtain a high frequency component to be emphasized by the difference between the blurred image and the high frequency component to the original image, thereby improving the contrast ratio of the image. In this paper, we design a Unsharp Mask Filter(UMF) that can process the contrast ratio improvement method of Unsharp Masking(UM) technique with one filtering. We adaptively process the contrast ratio improvement using Unsharp Mask Filter(UMF). We propose a method based on Retinex theory for adaptive processing. For adaptive filtering, we control the weights of Unsharp Mask Filter(UMF) based on the human visual system and output more effective results.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.4
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• pp.1-7
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• 2009

In this paper, the author presents the MIMO(Multi-Input Multi-Output) receiver algorithm with the capability of inter-cell or inter-sector interference cancellation over multi-antenna OFDM(Orthogonal Frequency Division Multiplexing) systems. As contrast with the previous research dealing with the filtering scheme at the time domain, the proposed algorithm is presented as the pre-filtering scheme which can be applicable to the frequency domain. Note that the proposed one can be implemented only by pilot symbols which are used in the channel estimation. In addition, it is analytically confirmed that the proposed scheme can be applied for either MIMO( C-SM(Collaborative-Spatial Multiplexing)) interference or SIMO(Single-Input Multi-Out) interference. The proposed receiver algorithm is verified by simulations over UL-PUSC SR off in IEEE 802.16e standard. From simulation results, it is confirmed that the proposed one can be applicable regardless of the kind of interference. Furthermore, it is verified that the performance is guaranteed even under Ole severe effect of interference and the improvement of system throughput is guaranteed.