• Journal of Broadcast Engineering
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• v.24 no.3
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• pp.485-494
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• 2019

A software-driven real-time frequency de-modulator is implemented with the aid of universal-serial-bus (USB) type software defined radio dongle. An analog stereo frequency modulation (FM) broadcast signal is down-converted to the basedband analog signal then converted to digital bit streams in the USB dongle. Computer software such as Matlab, Python, and GNU Radio manipulates the incoming bit streams with the technique of digital signal processing. Low pass filtering, band pass filtering, decimation, frequency discriminator, double sideband amplitude demodulation, phase locked loop, and deemphasis function blocks are implemented using such computer languages. Especially, GNU Radion is employed to realize the real-time demodulator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.9
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• pp.862-876
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• 1991

In this theses, the procedure for finding the equivalent immittance of an n-line coupled structures is presented in terms of the normal mode parameters of the n-line coupled system. The above generalized equations can be applied to the various Coupled structures including directional couplers, DC blocks, bandpass/band elimination filters, and various other uniformly coupled filters. The design equations are based on a simplified TEM(Quasi TEM) mode. The obtained results and the definition of the scattering parameters for a general coupled line four port with arbitrary terminations are used to present the procedure to determine the optimum physical dimensions matching the given load impedances connected to input, output port. Multiple coupled rnicrostrip two-port with three lines circuit designed shows little discrepancy between the conventional method and this one. Four port with five lines were fabricated on teflon substrate($e$r=2.55) with its thickness h=l.588mm designed at the center frequency, 4 GHz. Their measured results are fairly close to the ones by computation.

• Korean Journal of Optics and Photonics
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• v.13 no.2
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• pp.123-127
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• 2002

We have measured the wavelengths of the absorption lines of the $^{13}$ C$_2$H$_2$molecule by using a wavelength meter calibrated against the national optical frequency standard (iodine Stabilized He-Ne Laser, KRISS-R701) in the visible wavelength region. To measure the absolute wavelengths of the absorption lines, the frequency of the laser has been stabilized in the peaks and the sides of the absorption lines of $^{13}$ C$_2$H$_2$. Also, we have proposed the development of a frequency standard source of ITU-T grid using stabilization in the sides of the absorption lines of $^{13}$ C$_2$H$_2$.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.133_134
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• 2009

과거 국내 전력계통은 선진국에 비하여 주파수 품질이 현격하게 저하되어 계통운영자는 적정범위 이내로 주파수를 유지하는 것이 중요한 책무였다. 그러나, 계통수요와 계통연계의 지속적인 증가로 인하여 현행 주파수 유지율은 99.9% 수준에 근접하고 있다. 이러한 상황에서는 막대한 비용을 투자하여도 주파수 품질을 개선하기는 쉽지않다[1]. 주파수 유지율이 포화상태에 이른 주요 선진국들은 오래전부터 표준편차를 이용하여 주파수를 평가해오고 있다[2]. 따라서, 국내계통의 주파수 평가방법도 새로운 변화가 필요한 시점이다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.4
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• pp.337-346
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• 2014

This study aimed to understand the mode characteristics of a droplet subject to periodic forced vibration and the detachment of a droplet placed on a plate surface. An surface was coated with Teflon to clearly observe the behavior of a droplet. The contact angle between the droplet and surface and the hysteresis were found to be approximately $115^{\circ}C$ and within $25^{\circ}C$, respectively. The coating process was performed in a clean room that had an environment with a low level of contaminants and impurities such as air dust, detergents, and particles. To predict the resonance frequency of a droplet, theoretical and experimental approaches were applied. Two high-speed cameras were configured to acquire side and top views and thus capture different characteristics of a droplet: the mode shape, the detachment, the separated secondary droplet, and the waggling motion. A comparison of the theoretical and experimental results shows no more than 18 discrepancies when predicting the resonance frequency. These differences seem to be caused by contact line friction, nonlinear wall adhesion, and the uncertainty of the experiment. For lower energy inputs, the contact line of the droplet was pinned and the oscillation pattern was axisymmetric. However, the contact line of the droplet was de-pinned as the oscillation became more vigorous with increased energy input. The size of each lobe at the resonance frequency is somewhat larger than that at the neighboring frequency. A droplet in mode 2, one of the primary mode frequencies, exhibits vertical periodic movement as well as detachment and secondary ejection from the main droplet.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.5
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• pp.444-449
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• 2009

This paper presents the design of a dual band branch line hybrid coupler(BLHC) with different power division ratios at two bands. In the proposed design, transmission lines of the BLHC are transformed to $\pi$-type equivalent circuits which represent different impedances and $\lambda/4$ electrical length at two frequency bands. In order to verify the proposed method, a dual band coupler with different power division ratios is designed for 0.9 GHz and 2 GHz applications. The desired power division ratios are 1:1 and 1:3 at the two operating frequency bands. The measured results show excellent performance with an insertion loss of less than 0.33 dB, a return loss of less than -18.07 dB, and good isolation characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5B
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• pp.476-481
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• 2004

Since the bands 27.5 ∼ 28,350㎓ and 31.0 ~ 31.30Hz for existing fixed-satellite service were allocated to tile HAPS system in WRC-2000, the analysis on the interference effects between the existing FSS/GSO system and FS/HAPS system should be needed. To do study on the interference effects between above two systems, we can consider two frequency operational conditions, one is the Reverse mode, the other is Forward mode. In this paper, we analyzed the interference effects from airship of HAPS systems to satellite of the GSO system in the case of Reverse condition mode due to the C/I criterion, the latitude of HAPS and transmitting power of HAPS airship. In future, these results will be vital data to share between HAPS and GSO systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.1
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• pp.42-49
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• 2016

In this paper, we design and fabricate an instantaneous frequency measurement receiver with a frequency resolution of 125 MHz which detects and measures continuous signals in 4~6 GHz using path difference of delay lines. The receiver has a 4-bit configuration and consists of power dividers, delay lines, power combiners, power detectors, voltage comparator circuits and so on. The accuracy of the instantaneous frequency measurement is improved by applying offset voltage compensation to the comparator circuits to compensate the frequency-dependent path loss of the delay line and the frequency dependence of power detection.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.175-177
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• 2004

무전극 형광램프의 출력선 연장은 무전극 램프가 가지는 장수명 등의 이점을 최대화할 수 있는 방안이 된다. 하지만 이를 위해서는 연장에 따라 발생하는 요인들 -공진주파수의 변경, 온도변화에 따른 안정성 등을 고려하여 인버터의 설계가 이루어져야 한다. 이를 위해 본 연구에서는 ENDURA 150W 인버터의 출력선을 25m 연장하기 위해서 출력선을 고려한 공진 주파수를 설정하였고 온도변화에 따른 대책들을 제시하였다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.6
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• pp.80-83
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• 1982

A quarter-wavelength open circuited microstripline slot array is realized at X-band froquency. The optimal feeding point is experimentally determined. The input impedance of the slot array for various frequencies and its radiation pattern are measured. The bandwidth of the slot array is increased by using the 4$\times$4 elements which are slightly different in length and feeding network which is suggested in this papers.