• 조명전기설비학회논문지
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• 제25권11호
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• pp.98-102
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• 2011

This paper describes inverse E class frequency multiplier which is lower inductance and peak switching voltage than E class frequency multiplier. The frequency multiplier is designed to generate 5.8[GHz] frequency by doubling the input frequency 2.9[GHz]. The peak switching voltage of designed inverse E class frequency multiplier with 11[V] is lower 4[V] than that of E class frequency multiplier with 15[V]. The inverse E class frequency multiplier has a conversion gain 6[dB] at output power 21[dBm] and maximum 35[%] power efficiency.

• 한국컴퓨터정보학회논문지
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• 제20권11호
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• pp.111-118
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• 2015

In this paper, we propose a new tinnitus treatment system that removes the frequency band where the ear noises is generated and amplifies the around frequency bands in order to treat a nonstop buzzing in the ears, that is one among the disease commonly generated in modern people. Mostly the tinnitus is generated by the tunability with the neighboring nerves while the part of the cerebral cortex which is unable to react to the stimuli by the sound of the specific frequency band reacts to other frequency band. Therefore, the excitability activity by the tunability of the cerebral cortex is suppressed and the remedial value is gotten by removing the tinnitus frequency band, and the around frequency bands are amplified to strengthen the remedial value. Experimental results show that the tinnitus can be treated conveniently if the patients use the android application which the proposed technique is applied to.

• 한국통신학회논문지
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• 제13권1호
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• pp.54-62
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• 1988

본 논문에서는 부호분할다중접근을 위한 주파수도약대역확산통신방식의 통신시스템을 구현하는데 기본적으로 필요한 요소인 주파수합성기에 대하여 각 사용자에게 부여된 번지에 따라 원하는 도약형태로 주파수를 출력시키는데 적합하고 실제 시스템의 구현이 용이하도록 다중루프 PLL 주파수합성기의 모델을 제시하였으며 원하는 주파수를 출력시키는데 필요한 주파수분주정수의 분포와 그 결정방법, 그리고 이 분주정수와 다중도에 따른 대역통과필터의 대역폭의 변화에 대해 분석하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 춘계종합학술대회
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• pp.785-787
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• 2005

In the Bluetooth specification version 1.0, one specific frequency in one piconet was created depending upon the device clock and the Bluetooth native address at one specific time slot in the frequency hopping method. The basic hopping pattern was arranging the 79 ISM frequency band in pseudo-random fashion. Possible problem is the chance of collision of ownership of one specific frequency by more than 2 wireless devices when they are within the communication-active range. In this paper, we propose the adaptive frequency hopping method in order to resolve the possible problem so that more than 2 wireless devices communicates with their own client devices without being interfered. The proposed method was implemented with HDL later to be synthesized with an automatic EDA synthesizer and verified as well. The implemented adaptive frequency hopping circuit operated normally at 24MHz which will be the target clock frequency of the target Bluetooth device.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.437-440
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• 2008

In this paper, we present and analyze a robust frequency offset estimation scheme for orthogonal frequency division multiplexing (OFDM) systems over radio communication channels. When there exists frequency offset, the loss of orthogonality occurs and the interference problem among several subcarriers in OFDM signals is introduced. The guard interval of OFDM signals is employed for estimating the frequency offset. Furthermore, in order to enhance the frequency offset estimation performance, a ternary sequence is utilized. A frequency offset is estimated based on the synchronized correlator output. The proposed frequency offset estimation scheme can be applied to track the carrier frequency offset of OFDM systems.

• 한국소음진동공학회논문집
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• 제16권8호
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• pp.872-878
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• 2006

Mass estimation was derived as functions of acceleration magnitude and primary frequency. The conventional method of mass estimation used frequency data directly in the frequency domain. The signals that can be obtained sensor contained noise as well as impact signal. Therefore, how well we can detect the frequency data in noise directly determines the quality of mass estimation. To find exact frequency data, we used time-frequency analysis. The time-frequency methods are expected to be more useful than the conventional frequency domain analyses for the mass estimation problem on a plate type structure. Also it has been concluded that the smoothed WVD can give more reliable means than the other methodologies for the mass estimation in a noisy environment.

• 전자통신동향분석
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• 제34권6호
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• pp.1-16
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• 2019

The paper presents five strategic opinions for promoting the fourth industry revolution through the supply of 5G additional frequency. The assessments are on the basis of 5G frequency utilization technologies and services, with reference to 3GPP 5G New Radio standards, after investigating the domestic 1G, 2G, 3G, 4G, and 5G mobile communication services as well as the use of mobile radio frequency and spectrum. The presented opinions contain the frequency supply of contiguous-wide bandwidth channels, harmonized frequency supply between licensed and unlicensed spectrum, the existing 4G frequency recycle for increasing 5G coverage and capacity, balance frequency supply in the multi-band for 5G services, and the development of 5G vertical frequency for industry. The aim is that the presented five strategic opinions can offer guidance for the upcoming plan of domestic 5G additional frequency supply.

• 한국표면공학회지
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• 제57권4호
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• pp.348-354
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• 2024

Nanocrystalline zirconium nitride (ZrN) coatings were deposited by mid-frequency direct current sputtering (mfMS) with varying pulsed plasma parameters such as pulse frequency and duty cycle to understand the effect of pulsed plasma on the microstructure, residual stress and mechanical properties. The results show that, with the increasing pulse frequency and decreasing duty cycle, the coating morphology changed from a porous columnar to a dense structure, with finer grains. Mid-frequency magnetron sputtered ZrN coatings with pulse frequency of 30 kHz showed the highest both nanoindentation hardness of 16.3 GPa, and elastic modulus of 214.4 GPa. In addition, Effect of pulse frequency on a residual stress and average crystal grain sizes was also investigated.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권3호
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• pp.941-955
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• 2015

In dual-channel networks (DCNs), all frequency hopping (FH) sequences used for data channels are chosen from the original FH sequence used for the control channel by shifting different initial phases. As the number of data channels increases, the hitting frequency point problem becomes considerably serious because DCNs is non-orthogonal synchronization network and FH sequences are non-orthogonal. The increasing severity of the hitting frequency point problem consequently reduces the resource utilization efficiency. To solve this problem, we propose a novel hitting frequency point collision avoidance method, which consists of a sequence-selection strategy called sliding correlation (SC) and a collision avoidance strategy called keeping silent on hitting frequency point (KSHF). SC is used to find the optimal phase-shifted FH sequence with the minimum number of hitting frequency points for a new data channel. The hitting frequency points and their locations in this optimal sequence are also derived for KSHF according to SC strategy. In KSHF, the transceivers transmit or receive symbol information not on the hitting frequency point, but on the next frequency point during the next FH period. Analytical and simulation results demonstrate that unlike the traditional method, the proposed method can effectively reduce the number of hitting frequency points and improve the efficiency of the code resource utilization.

• Journal of Electrical Engineering and Technology
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• 제6권4호
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• pp.439-446
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• 2011

Frequency is an important operating parameter for the protection, control, and stability of a power system. Thus, it must be maintained very close to its nominal frequency. Due to the sudden change in generation and loads or faults in a power system, however, frequency deviates from its nominal value. An accurate monitoring of the power frequency is essential for optimum operation and prevention of wide area blackout. Most conventional frequency estimation schemes are based on the DFT filter. In these schemes, the gain error could cause defects when the frequency deviates from the nominal value. We present an advanced frequency estimation technique using gain compensation to enhance the DFT filter-based technique. The proposed technique can reduce the gain error caused when the frequency deviates from the nominal value. Simulation studies are performed using both the data from EMTP-RV software and the user-defined arbitrary signals to demonstrate the effectiveness of the proposed algorithm. Results show that the proposed algorithm achieves good performance under both steady state tests and dynamic conditions.