• Electronics and Telecommunications Trends
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• v.7 no.4
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• pp.71-88
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• 1992

전기통신 회선의 2 선 선로 임피던스와 하이브리드 회로의 평형 결선망과의 임피던스 부정합에 의한 반사손실의 영향을 파악하고 과도한 중계기 이득과 이들 임피던스 부정합으로 인한 통신망의 위해요소인 명음의 발생 배경과 명음 발생 방지를 위한 세계 각국의 관련기준 및 측정법을 조사 분석한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.12
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• pp.1266-1273
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• 1991

Attenuation losses and repeater spans of single-mode optical fibers installed in the long hual optical transmission line were measured and analyzed. The average loss including splicing points was appeared to be 0.55 0.05dB/km and 0.59 0.01dB/km at 1300nm and 1550nm, respectively, and showed lager value at 1550nm window, The cause of loss increase at 1550nm range from the OTDR measurement was due to the inappropriate treatment of extra length of fiber at the splicing points. And average repeater span of domestic long haul line was 24 7km and 90% of total sampled repeater spans was within 31 km.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.4
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• pp.549-554
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• 2017

In this paper, we studied the design and fabrication of $2{\times}2$ microstrip array antenna at around 5 GHz band.. To improve of frequency properties of antenna, feed microstrip patch antenna was simulated by HFSS(High Frequency Structure Simulator). A $2{\times}2$ array antenna was designed and fabricated by photolithograph on an FR4 substrate (dielectric constant of 4.4 and thickness of 1.6 mm). The fabricated $2{\times}2$ array antenna showed a center frequency, the minimum return loss and bandwidth were 5.3 GHz, -24dB, and 390MHz, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.8
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• pp.741-747
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• 2002

In this paper, NRD guide band pass filter with newly designed inductive iris structure is proposed and analyzed with its test results. In case of common NRD guide filter with air gap coupled structure, it was not easy to fabricate and process or each NRD guide dielectric resonator blocks using PTFE. However, in this our research, each dielectric resonator fabricated in a single NRD guide is coupled with inductive iris located on metal plates. The structure is suitable for mass production of a precise and reliable millimeter-wave filter applications. As a result of measurements, designed NRD guide inductive iris filter has superior performance. The pass band is 38.66~39.06 MHz with 400 MHz bandwidth, insertion loss is about 1.4 dB and return loss is below -18 dB.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.5
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• pp.724-730
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• 2002

Digital communication systems are required to cause the minimum interference to adjacent channels, they must therefore employ the linear power amplifiers. In respect to linear power amplifiers, there are many linearization techniques. Feedforward power amplifier represent very wide bandwidth and high linearization capability. In the feedforward systems, overall efficiency is reduced due to the loss of delay line. In this paper, delay filter instead of transmission delay line adapted to get more high efficiency. Experimental results showed that ACLR (Adjacent Channel Leakage Ratio) has improved 17.43(dB), which is added 3.44(dB) by using the delay filter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.1
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• pp.54-59
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• 2019

In this paper, we report on the waveguide-to-microstrip transition with an inline structure for the millimeter band. The waveguide-to-microstrip transition comprises a probe, an inductive line, a ${\lambda}/4$ impedance transformer, and a 50-ohm microstrip line. For the transition design, we optimized the characteristic impedances and lengths of the component parts. The fabricated transition exhibits an insertion loss of 2.1 dB and an input/output return loss of below 13 dB at a millimeter band frequency of 94 GHz.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.3
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• pp.302-311
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• 2014

In this work, a FTTL (fishbone-type transmission line) structure was fabricated on PES (polyether sulfone) for a realization of transparent flexible wireless communication device, and its RF characteristics were investigated. According to the results, the FTTL on PES showed a short wavelength characteristic compared with conventional coplanar waveguide. Concretely, the wavelength of the FTTL was 2.23 mm at 50 GHz, which was 56.6 % of the conventional coplanar waveguide. According to the bandwidth extraction result, the passband of the FTTL on PES was 608 GHz. Unlike conventional periodic structures, the characteristic impedance of the FTTL on PES showed a very low frequency dependency, which means that the FTTL on PES can be used for application to transmission line and distributed passive components with a broadband operation frequency.

• Journal of the Korean Magnetics Society
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• v.17 no.6
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• pp.242-245
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• 2007

Conduction noise attenuation by composite sheets of high magnetic and dielectric loss has been analyzed by using electromagnetic field simulator which employs finite element method. The simulation model consists of microstrip line with planar input/output ports and noise absorbers (magnetic composite sheets containing iron flake particles as absorbent fillers). Reflection and transmission parameters $(S_{11}\;and\;S_{21})$ and power loss are calculated as a function of frequency with variation of sheet size and thickness. The simulated value is in good agreement with measured one and it is demonstrated that the proposed simulation technique can be effectively used in the design and characterization of noise absorbing materials in the RF transmission lines.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.7
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• pp.721-727
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• 2014

In this paper, an broadband Schiffman phase shifter is proposed using vertically installed coupled lines. It consists of the typical coupled lines and a extra coupled lines which is installed vertically on the original coupled lines plane. Phase responses of Schiffman phase shifter with vetically installed coupled lines are analyzed in consideration of the phase velocity of two independent transmission modes and the characteristic impedances. The $90^{\circ}$ Schiffman phase shifters with high impedance ratio is realized at 2.4 GHz, which cannot be implemented with the conventional coupled lines. The measured results show that the bandwidth is 1.5~3.2 GHz(70.8 %) within the phase errors ${\pm}5^{\circ}$. The measured return loss is found to be better than 12.4 dB and insertion loss is less than 1.2 dB over the operating frequency band.

• 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.