• Journal of information and communication convergence engineering
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• 제14권3호
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• pp.147-152
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• 2016

In radio-over-fiber (RoF) systems, nonlinear compensation is essential to improve performance. Among the several existing nonlinear compensation techniques, we investigate a predistortion technique for a directly modulated laser in an RoF system. First, we obtain the input-to-output response of a directly modulated laser at 160, 820, and 1,540 MHz. The results show that the laser response is dependent on the frequency band. Second, we design an optimal predistortion circuit to compensate for the nonlinear responses of three frequency bands. We design the predistortion circuit with two options: each predistortion circuit for each frequency band and one single predistortion circuit for all the three frequency bands. Finally, we present the simulation results of the predistortion system obtained using a commercial simulator. These results show that the third intermodulation distortion (IMD3) is improved by 0.6-9 dB for the three frequency bands with only a single predistortion circuit.

• ETRI Journal
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• 제29권6호
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• pp.725-735
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• 2007

This paper describes a line element planar antenna with three frequency bands. To obtain broadband characteristics, a modified planar antenna that has semi-elliptical elements based on the characteristics of a line element planar antenna is proposed and analyzed by the finite difference time domain method. Return loss characteristics are discussed as functions of the eccentricity values of semi-ellipse at each element. The broadbanding of the modified planar antenna is implemented based on the results. The planar antenna with three systems (an 800 MHz band cellular phone, a third-generation cellular phone, and a 2.4 GHz band wireless LAN system) is considered as an application example.

• 한국소음진동공학회논문집
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• 제17권5호
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• pp.398-404
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• 2007

In this study, the sensitivity of annoyance was investigated by the subjective jury test for the variations of the frequency components along with various sound pressure levels of sixteen environmental noise sources. Annoyance was, also, evaluated for the road traffic noises. Sound pressure levels were $54{\sim}84\;dB$ which individually divided frequency components with eight bands of equally three bark bands. The results show that vehicle traffic noise is recognized as the most serious environment noise source. The sensitivity of human perception of annoyance in frequency bands is quite different from A-weighting curve. The annoyance found out to be more sensitive in high frequency region and reached its maximum in 3.4 kHz.

• 대한전자공학회논문지
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• 제22권1호
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• pp.46-52
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• 1985

작은 채널 간격 및 많은 채널수를 갖고 3개의 서로 다른 대역에서 스위프를 하는 모듈러 (modulo) 함수를 이용하여 주파수 합성방식을 설계하였다. 그러므로 본 연구에서 설계한 전력제어발진기는 스펙트럼 분석기에서 필요한 3개의 각각 다른 대역폭과 채널 간격이 10Hz, 40Hz, 400Hz로써 512개의 채널수를 갖는 장치에 적합하다.

• 대한의용생체공학회:의공학회지
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• 제28권1호
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• pp.55-65
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• 2007

This paper sought to investigate pupil size variability, pupil size parameters in terms of time domain and frequency domain, the autonomic activity change induced by posture change, degree of sleepiness and cognitive task (math task). With a specially designed pupil image acquisition system in the dark room, these three kinds of experiments were performed to induce a dominant state of sympathetic or parasympathetic activation. Electrocardiogram and pupil size were measured in all the experiments. Based on three experiments, we calculated heart rate variability. In the pupil size analysis, we calculated the mean and standard deviation of pupil size (in time domain), and proposed several frequency bands that exhibit different autonomic activation between different sessions. The results indicate that in terms of heart rate variability, posture change exhibited significant differences but not between sleepiness level, or between cognitive task. Pupil sizes differed only during the postures. And we found some frequency bands that correlated with autonomic activation in each experiment. While heart rate variability reflects posture change that need cardiac control, pupil size variability reflects not only posture induced autonomic activation but sleepiness and cognitive load, which is processed in the brain, in time and frequency domain parameter.

• 전력전자학회논문지
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• 제20권2호
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• pp.137-143
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• 2015

This paper presents the intra capacitance modeling based on the winding method and section bobbin for CM choke capable of EMI attenuation of broad bands from lower to higher frequency bands and high frequency type common-mode choke capable of EMI attenuation of high frequency band used in the EMI Block of LED-TV SMPS. The case of high frequency type CM choke can be explained by the parasitic capacitance of three types of CM choke. The winding method of section bobbin type is smaller than the others. The first resonant frequency of the proposed CM choke tends to increase as the parasitic capacitance becomes small and its impedance characteristics improved performance as the first resonant frequency increases. The CM chokes of the proposed section bobbin type shows that in the future, the method may have practical use in LED/LCD-TV SMPS and in several applications, such as LED lighting, adapters, and so on.

• 한국산학기술학회논문지
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• 제12권6호
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• pp.2770-2776
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• 2011

본 논문은 DTV 주파수 대역(185 MHz, 481 MHz, 687 MHz)에 WiBro와 무선랜 서비스가 동일 채널 및 인접 채널에 할당되는 시나리오를 가정한 후, Monte-Carlo 기반의 Spectrum Engineering Advanced Monte Carlo Analysis Tool(SEAMCAT)을 이용한 간섭 분석을 통해 최적의 주파수 대역을 제시하였다. 분석 내용으로 WiBro Mobile Station과 무선랜 User Equipment 사이의 요구되는 보호거리 및 보호 대역, WiBro Mobile Station/Base Station 및 무선랜 User Equipment 의 허용 송신 파워를 분석하였다. 분석 결과, 주파수 대역 185 MHz에 할당할 경우가 상대적으로 잠재적 간섭이 가장 큰 경우이고 697 MHz의 할당이 최적의 주파수 대역으로 분석되었다. 본 분석결과는 향후 DTV 주파수 대역에 WiBro와 무선랜의 할당에 유용하게 활용될 것으로 기대된다.

• 한국항행학회논문지
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• 제26권1호
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• pp.29-34
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• 2022

본 논문에서는 2.45 GHz 및 5 GHz 무선 랜 주파수 대역과 3.5 GHz WiMAX 주파수 대역에서 동작하는 삼중 다이폴 준-야기 안테나의 설계에 대하여 연구하였다. 제안된 준-야기 안테나는 V-모양 접지면과 직렬로 연결된 세 개의 다이폴로 구성된다. 길이가 가장 긴 반-보우타이 모양의 다이폴은 2.45 GHz 대역에서 공진하고, 중간 길이의 다이폴은 3.5 GHz에서 공진한다. 길이가 가장 짧은 다이폴은 5 GHz 대역에서 공진한다. 다이폴의 길이와 폭, 다이폴 사이의 간격을 조절하여 2.45 GHz, 3.5 GHz 및 5 GHz 대역에서 동작하는 삼중 대역 지향성 안테나를 설계하였고, FR4 기판 상에 45 mm × 55 mm 크기로 제작하였다. 제작된 안테나는 전압 정재파비가 2 이하인 대역이 2.32-2.57 GHz, 3.26-3.69 GHz, 4.50-6.56 GHz로 설계된 삼중 대역에서 동작하는 것을 확인하였다. 이득은 세 대역에서 3 dBi 이상을 유지하였다.

• Journal of electromagnetic engineering and science
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• 제15권1호
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• pp.6-13
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• 2015

In this paper, a novel monopole antenna for WLAN/WiMAX application is presented. The proposed antenna consists of two arc-shaped strips, a vertical strip, and a slot in the ground plane. In this study, a prototype of the proposed triple-band antenna was designed, fabricated, and tested. The quantitative and experimental results demonstrate that the proposed antenna satisfy the -10 dB impedance bandwidth requirement of 440 MHz for 2.4/2.5 GHz bands (from 2.26 to 2.70 GHz), 970 MHz for 3.5 GHz bands (from 3.27 to 4.24 GHz), and 870 MHz for the GHz bands (from 5.08 to 5.95 GHz), while simultaneously covering the WLAN and WiMAX bands. In addition, the presented triple-band antenna has an omnidirectional radiation pattern at all three frequency bands with an antenna gain of 4.45 dBi for the lowest band, 2.04 dBi for the middle band, and 3.98 dBi for the highest band.

• 천문학회보
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• 제39권1호
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• pp.45.1-45.1
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• 2014

We present the results of a time series analysis of the long-term radio lightcurves of four blazars: 3C 279, 3C 345, 3C 446, and BL Lacertae. We exploit the data base of the University of Michigan Radio Astronomy Observatory (UMRAO) monitoring program which provides densely sampled lightcurves spanning 32 years in time in three frequency bands located at 4.8, 8, and 14.5,GHz. Our sources show mostly flat or inverted (spectral indices -0.5 < alpha < 0) spectra, in agreement with optically thick emission. All lightcurves show strong variability on all time scales. Analyzing the time lags between the lightcurves from different frequency bands, we find that we can distinguish high-peaking flares and low-peaking flares in accord with the classification of Valtaoja et al. (1992). The periodograms (temporal power spectra) of the observed lightcurves are consistent with random-walk powerlaw noise without any indication of (quasi-)periodic variability. The fact that all four sources studied are in agreement with being random-walk noise emitters at radio wavelengths suggests that such behavior is a general property of blazars.