• Journal of the Korea Society of Computer and Information
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• v.23 no.12
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• pp.27-33
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• 2018

In this paper, we propose an efficient edge preserving smoothing filter for Infrared image that can reduce noise while preserving edge information. Infrared images suffer from low signal-to-noise ratio, low edge detail information and low contrast. So, detail enhancement and noise reduction play crucial roles in infrared image processing. We first apply a guided image filter as a local analysis. After the filtering process, we optimization globally using relativity of guided image filter. Our method outperforms the previous methods in removing the noise while preserving edge information and detail enhancement.

• Current Optics and Photonics
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• v.7 no.5
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• pp.557-561
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• 2023

Ultralow-noise soliton pulse generation over a wider Fourier frequency range is highly desirable for many high-precision applications. Here, we realize a low-phase-noise soliton pulse generation by transferring the low phase noise of a mode-locked laser to a silica microcomb. A 21.956-GHz and a 9.9167-GHz Kerr soliton combs are synchronized to a 2-GHz and a 2.5-GHz mode-locked laser through a fractional optoelectronic phase-locked loop, respectively. The phase noise of the microcomb was suppressed by up to ~40 dB at 1-Hz Fourier frequency. This result provides a simple method for low-phase-noise soliton pulse generation, thereby facilitating extensive applications.

• Journal of electromagnetic engineering and science
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• v.16 no.3
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• pp.191-193
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• 2016

This paper proposes a voltage-controlled oscillator (VCO) that has broadband turning and low-level of phase noise characteristics. Due to the micro-strip line resonant circuit with a low Q value, which is applied to the broadband tuning range, the depreciated phase noise performance is compensated by restraining the harmonics of the oscillating frequency. The VCO was designed according to the proposed structure as well as the conventional structure, and the superiority of the proposed structure was verified through its simulation, fabrication, and measurement.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.621-624
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• 2003

In this paper, two Cascode Low Noise Variable Gain Amplifiers are proposed for wide dynamic range and constant Noise Figure for frequency range of 2.4GHz. Designed Variable Gain Low Noise Amplifier are for Wireless Local Area Network (WLAN) applications. A gain is higher than 17dB and the noise figure is approximately 1.3dB and the input VSWR is better than 2:1.

• Journal of the Korean GEO-environmental Society
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• v.11 no.7
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• pp.15-24
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• 2010

Noise and vibration due to pile driving cause residents nearby construction sites to file civil complaints and to the extent of bringing construction to a halt. To deal with this issue, construction engineers have worked strenuously to develop several types of low noise & low vibration pile methods. In this study, a new noise and vibration-free precast screw pile method proposed as a low noise & low vibration pile. It penetrates into the ground by rotating and pressing to avert noise and vibration while maximizing bearing capacity. A prototype of noise and vibration-free precast screw pile method was manufactured, which is not seen anywhere in Korea and elsewhere, and have undergone pilot tests twice to determine construction method. Based on this study, features of the noise & vibration-free screw pile method, production of screw concrete pile prototype, two pilot tests and subsequent construction method were determined.

• Korean Journal of Remote Sensing
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• v.30 no.4
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• pp.505-510
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• 2014

Normalized Difference Vegetation Index (NDVI) is a major indicator for monitoring climate change and detecting vegetation coverage. In order to retrieve NDVI, it is preprocessed using cloud masking and atmospheric correction. However, the preprocessed NDVI still has abnormally low values known as noise which appears in the long-term time series due to rainfall, snow and incomplete cloud masking. An existing method of using polynomial regression has some problems such as overestimation and noise detectability. Thereby, this study suggests a simple method using amoving average approach for correcting NDVI noises using SPOT/VEGETATION S10 Product. The results of the moving average method were compared with those of the polynomial regression. The results showed that the moving average method is better than the former approach in correcting NDVI noise.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.1
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• pp.57-65
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• 2017

This paper presented a method of designing low-power feedback active noise control filter optimized for headphones/earphones. Using constrained optimization, we obtained a high order FIR noise control filter to ensure reasonable noise attenuation performance at high sampling frequency environment. Then using infinite impulse response (IIR) approximation method called Balanced Model Truncation (BMT), we obtained a low order IIR noise control filter suitable for low-power digital signal processing system like headphones/earphones. For further performance improvement, we utilized frequency warping method so that we could obtain more accurately approximated IIR filter and we ensured system stability by reconstructing the low order IIR filter in form of cascaded second order IIR filters. ANC simulation with white noise and stability test verified that the proposed algorithm had superior attenuation performance and better robustness compared to the conventional algorithm.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.196-199
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• 2000

In this paper, we have designed a low-noise amplifier for the down-converter to apply the K-band Mu-kung-hwa satellite downconvertion. We have designed on three-stage to satisfy the property of low-noise amplifier for the down-converter required at least 30dB gain. The simulaition results for the designed three-stage Low-noise amplifier are measured that 33dB, gain and 0.93dB, noise-figure From 19.200 to 20.200, and The experiment results of the fabric are measured that 25dB, gain and 1.5dB, noise-figure. Since Input reflection coefficient and otput resection coefficient are -25dB and -28dB, respectively, and VSWR is lower than 1.5, this amplifier can be used as a low-noise amplifier for the down-converter to apply the K-band Mu-kung-hwa satellite downconvertion.

• Journal of the Korean Magnetics Society
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• v.11 no.3
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• pp.134-140
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• 2001

Flux-gate magnetometer was developed in 1930's, and it has been widely used for the low magnetic field measurements. In this work, we have employed amorphous ribbon 2714A produced by Allied Chem. Co. as sensor core material. To develop low noise, low power consumption, and high reliability flux-gate magnetometer, we have measured ac magnetic properties depending on the annealing conditions. As quenched state amorphous core shows high noise level and ac magnetic properties were changed under the condition of accelerated aging test, but amorphous ribbon, which was annealed under 350 $\^{C}$ during 1 hour, shows low noise level of 0.1 nT in the frequency range of dc∼10 Hz which was 10 times better than the as quenched amorphous ribbon. Under accelerated aging test, ac magnetic properties such as squareness and coercivity of the annealed samples show higher reliability and approached to a certain limiting value as exponential function. We can see that high reliability and low noise flux-gate magnetometer could be developed, if we consider this ac magnetic properties change in the sensor design.

• Journal of the Korean Society for Railway
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• v.19 no.2
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• pp.124-134
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• 2016

Research on low height noise barriers installed adjacent to railways to reduce the height of the noise barrier has actively progressed in many countries except Korea. The performance of low height noise barriers is evaluated to identify barrier acoustic characteristics using a scale model of the barrier in the present research. As shown in the experimental results, if it is considered the installation of 'ㄱ' type noise barrier, sound absorption material should be installed on both the top and the vertical surfaces of the barrier to improve insertion loss. Also, an analytical method such as the boundary element method, rather than a simple empirical equation, is required to evaluate the insertion loss of the barrier. In addition, noise level increase in passenger position is very small if a barrier with sound absorption material is installed. Finally, the two dimensional boundary element method is implemented to predict the acoustic characteristics of the low height barrier; the possibility of the application is confirmed from a comparison of the results of measurements and predictions.