• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.1 s.343
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• pp.133-142
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• 2006

This paper suggests an efficient method of protection ratio(PR) calculation and shows some results of point-to-point radio relay system for frequency coordination. The proposed PR can be expressed as a function of C/N of modulation scheme, noise-to-interference ratio(N/I), multiple interference allowance, fade margins of multi-Path and rain attenuation and net filter discrimination. And PR calculation is performed in view of fade margin, modulation scheme, distance, and interference for actual point-to-point radio relay frequency. According to results for 6.2 GHz, 64-QAM and 60 km at BER 10-6, fade margin and co-channel Protection ratio reveal 41.1dB and 74.9 dB, respectively The merit of presented method provides a systematic and easy calculation by means of PR correction factor related with various parameters and can apply the same concept to frequency coordination of millimeter wave radio relay system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.4
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• pp.514-522
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• 2000

In this thesis, a two-dimensional active phased array antenna without phase shifter is studied for two-dimensional beam scanning. A designed two-dimensional oscillator-type active array antenna, radiation elements and the oscillator circuits were combined with via-hole and coupled by slot on the opposite ground plane. The operating characteristics are analyzed and experimentally demonstrated , The two-dimensional $4\times4$ elements were designed for the proper coupling strengths and coupling phases by adjusting the width, length and offset position of slot-lines. The fabricated active phased array antenna shows the beam shift characteristics capable of scanning from $-17^{\circ}$ to $18^{\circ}$ with respect to broadside in one dimension, from $-5^{\circ}$ to $10^{\circ}$ in two dimension. The experimental results show that it is possible to use the oscillator-type active phased array antenna as a two-dimensional planar array antenna.

• The Journal of the Acoustical Society of Korea
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• v.24 no.5
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• pp.238-247
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• 2005

In this Paper. we Presents subband design techniques of a compensating filter and adaptive feedback canceller for the digital hearing aid. The sensorineural hearing loss has a hearing threshold that shows a nonlinear characteristic in frequency domain. and its compensation suffers from an echo that produced by an undesired time varying feedback path. Therefore. the digital hearing aid requires the compensator that can adjust gains nonlinearly in frequency bands and eliminate the echo rapidly In the Proposed digital hearing aid. the compensating filter is designed by the adaptive system identification method in subband structure, and the adaptive feedback canceller is designed by the subband affine projection algorithm. The designed compensation filter can control the nonlinear gain in each subband respectively, therefore precise compensation is possible. And the feedback canceller using the subband adaptive filter achieves fast convergence rate. The Performances of the Proposed method are verified by computer simulations as comparing with the behaviors of the previous trials.

• Journal of IKEEE
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• v.25 no.4
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• pp.721-727
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• 2021

This paper proposes a UWB (Ultar-wideband) impulse generator using the gated ring oscillator. The oscillator and PLL circuits which generate a several GHz LO signal for the conventional architecture are replaced with the gated ring oscillator. Therefore, the system complexity is decreased. The proposed architecture controls the duty of enable signal, which is used for the head switch of ring oscillator. The control of the duty enables to tun off the oscillator during the guard interval and stop wasting the power consumption. The pulse shaping method using the counter makes the small side lobe and preserves the bandwidth regardless of the change on the center frequency. Designed UWB impulse generator could change the center frequency from 6.0 GHz to 8.8 GHz with a digital bit control, while it preserves the bandwidth as about 1.5 GHz.

• Journal of the Korean Institute of Telematics and Electronics
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• v.9 no.5
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• pp.19-26
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• 1972

A newly developed quartz frequency modulator utili3ing a V. V. C. diode is briefly described. Its electrical characteristics-including modulation linearity, modulation distortion, and carrier frequency stability depending upon the variation of the environmental temperature and the applied power voltage, etc.-are suitable for the modulator of a mobile or a portable F.M. transmitter according to the experimental results. The excellent over-all electrical characteristics were proved from the experimental development of the two kinds of transceivers. One is the single channal transceiver which contains a direct frequency modulator at the carrier frequency of 52.750 MHg. The other is the dual channel transceiver (the frequencies are selected from about 40 channels without tuning adjustment) whose operational frequency is composed of a modulated frequency of 10.7 MHz and the frequency generated at a channel control oscillator, As mentioned above, it is realized that the electrical characteristics of this modulation method are suitable for portable F. M. transceivers.

• Journal of the Korea Society of Computer and Information
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• v.26 no.8
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• pp.1-11
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• 2021

This paper proposes a novel mechanism called Event-driven Uncore Frequency Scaler (eUFS) to improve the energy efficiency of the HPC systems. UFS exploits the hardware events such as LAPI (Last-level Cache Accesses Per Instructions) and CPI (Clock Cycles Per Instruction) to dynamically adjusts the uncore frequency. Hardware events are collected at a reference time period, and the target uncore frequency is determined using the collected event and the previous uncore frequency. Experiments with the NPB benchmarks demonstrate that the eUFS reduces the energy consumption by 6% on average for class C and D NPB benchmarks while it only increases the execution time by 2% on average.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.4
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• pp.504-511
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• 2012

In this paper, level instrument is implemented using beat frequency for distance measurement which means the difference between Tx and Rx signal frequency from FMCW Radar Level Transmitter. Beat frequency is analyzed through Fast Fourier Transform of which frequency precision can be improved by applying Zoom FFT. Distance precision is improved from 146.5[mm] to 5[mm] using the advantage of Zoom FFT which can raise the frequency precision without changing the sampling frequency or FFT point number to be fixed in the beginning of designing signal processing. Also, measurement error can be reduced within 2[mm] by incresing the FFT points using the method of Spline interpolation. For verifying the effectiveness of this Zoom FFT to FMCW Radar Level Transmitter, test bench is made to measure the distance for every 1[mm] between 700[mm] and 2000[mm] and measurement error can be checked in the range of ${\pm}2$[mm].

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.6
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• pp.512-520
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• 2016

In this paper, a miniaturized frequency selective surface(FSS) for bandstop operation that provides stability for an angle of incidence and polarization is presented. The proposed miniaturized FSS has the unit cell of hexagonal structure with triangular loops and size of the unit cell is $0.081{\lambda}{\times}0.081{\lambda}$ at 2.5 GHz operating frequency, which is very small compared to operating wavelength. In addition, unlike the conventional design, which requires complicated design parameters, the proposed FSS is easily expanded to the desired operating frequency for 2~8 GHz, by controlling the specific design parameters. To validate the simulation results, the FSS structures having different operating frequencies, 2.5 GHz, 5 GHz and 8.2 GHz were designed, fabricated and measured. The comparisons between the simulation and the measured results show good agreement. The proposed miniaturized FSS can provide better frequency stability for different incidence angles and polarizations.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.522-529
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• 2007

A semidynamic frequency divide-by-1.5 MMIC comprises a tunable polyphase filter, tunable image-rejection mixer, and a static divide-by-2 in the feedback path. Wideband suppression of unwanted tones is achieved by employing a tunable image-rejection mixer and a tunable single-stage polyphase filter. Implemented in GaInP/GaAs HBT technology, the divide-by-1.5 MMIC operates over the input frequency range of 4.5 to 9.2 GHz with better than -20 dBc suppressions of $1/3{\times}f_{in}\;and\;f_{in}$ tones, while dissipating 29 mA from 4.1 V supply.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.131-136
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• 2008

Using ultrasonic standing waves, micro particles submerged or flowing in fluid can be manipulated. Due to acoustic radiation force of ultrasound, particles are forced to move to pressure nodal or antinodal lines. In this work, we propose a method to control the position of micro particle in a flow by adjusting the frequency of the standing wave. To this end, standing wave field generation system including a few millimeter thick micro channel was established using an immersible ultrasonic transducer. The present generation system works valid in a frequency range between 2.0 MHz and 2.5 MHz. We observed the SiC particles in water moved to pressure nodal lines by the standing wave. The effect of the channel thickness and operating frequency was also investigated. Interestingly, it was shown that the operating frequency have a close relation with the location of the pressure nodal line. Consequently, it fan be said that the position of particle movement rail be controlled by adjusting the ultrasound frequency. The maximum range of the controllable position was about 261 micrometers under the given condition. The resulted observations reveal the possibility of various applications of the ultrasonic standing wave to the manipulation of particles submerged in a fluid.