• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.3
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• pp.25-30
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• 2020

This study is to provide high-quality mobile communication service to subscribers and wireless communication users in a Mobile communication environment. It is about a method to secure the quality of a call by early processing a faulty radio station. The purpose of this study is to design and implement a direction detection system suitable for a mobile communication environment and portable as a method for early detection and resolution of interference and illegal wireless stations occurring in 5G mobile communication. The basic configuration of a portable direction detection system was designed, and a method was proposed to find and repair a faulty wireless station in a short time through manufacturing and experimentation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.3
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• pp.239-254
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• 1988

In this paper an exciter which performs modulation and amplification is composed of high power(30dBm) VCO(Voltage Controlled Oscillator) using push-pull circuit. Modulation is FSK using PLL(Phase Locked Loop). A single loop PLL synthesizer having sequency range of 42.5-100.5MHz, 25KHz channel spacing and switching time of 1msec converts down the exciter VCO frequency to 1.25MHz. This signal mixed with the FSK modulated signal coming in the phase detector of exciter. The acquisition time of exciter for frequency hoppng is less than 200usec, so the total acquisition time for transmission is less that 1.5msec. There is no need of additional power amplification because power amlifiction by high power VCO is high enough to communicate within near distance. The proposed frequency synthesizer is not complex so it is suitable for low cost slow frequency hopping spread spectrum communication.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.4
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• pp.29-40
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• 2004

This paper reports the frequency characteristics and the time response of parallel adjacent-transmission lines, crossed adjacent-transmission lines and parallel adjacent-transmission lines which are on the different planes by using FDTD-PML method. In the parallel adjacent-transmission lines, the crosstalks as a function of horizontal distance are calculated and in the crossed adjacent- transmission lines, the crosstalks as a function of vertical distance are simulated. Also, the crosstalks as functions of horizontal and vertical distances are measured and analyzed in the parallel adjacent-transmission lines which are on the different planes.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.2
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• pp.333-339
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• 2012

Global flow of communication is a trend of high speed, digitalization, and high-capacity. Furthermore, spread spectrum method has been dominantly utilized to efficiently use the frequency which is the scarce resource. The PLL (Phase Lock Loop) which is a widely used frequency synthesizer in communication systems has few problems such as status interferences and hence, this study utilized the DDS (Direct Digital Synthesis) which is a digital device that can minimize the problems of PLL for the study on the performance evaluation of high speed frequency hopping system design. We designed a system that practices high speed frequency hopping and interprets improvement of error-rates and evaluated its performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.8 no.4
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• pp.164-171
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• 1983

In this paper, angular division multiplexing of the optical multiplexing technique for transmitting several channels using a relatively short step-index fiber is described. Mode coupling and the output power distributionin the fiber for the plane wave excitations is calculated and the crosstalk level determination of the system is proposed. In the presence of the mode coupling, the pulse width in terms of the fiber's length and input condition is calculated in the slab waveguide and the fiber. For the input angles (

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.1-7
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• 2013

In the next generation of mobile communication systems, high data rates and high capacity will be possible if multiple antennas are used at new frequencies. This paper presents the correlations between channel parameter path loss (PL), delay spread (DS), angular spread (AS) and K-factor established based on channel measurements. To avoid interference from Korean DTV broadcasting, we measured the channel characteristics in urban/rural/suburban areas on Jeju Island using a channel sounder and $4{\times}4$ antennas. The correlations between channel parameter show that the wireless channel characteristics can be determined and effective communication system design can be produced for use in similar environments.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.5
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• pp.775-781
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• 2011

For the measurement of absolute position of mobile robot in indoor environments, the ultrasonic positioning systems using ultrasound have been researched for several years. Most of these ultrasonic positioning systems to avoid interference between the ultrasound are used for sequential transmitting. However, due to the use of sequential transmitting, the positions of transmitter to receive an ultrasound will change when the mobile robot moves. Therefore the accuracy of positioning is reduced. In this paper, the new position estimation algorithm with weighting factor according to the time of receipt is proposed. By applying the proposed algorithm to existing Ultrasonic Satellite System(USAT), the improved USAT is configured. The positioning performance of the improved USAT with the proposed position estimation algorithm are verified by experiments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.8
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• pp.878-887
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• 2012

Aeronautical frequency band is to be internationally protected for aviation safety. Recently, with a rapid growth of an international air traffic, aeronautical frequency band is getting saturated, and thus may causes the interference in the congested frequency band. In this paper, an efficient aeronautical frequency allotment and management policies are proposed for resolving the existing problems in the aeronautical frequency band. The key activities include the review of the aeronautical frequency management and interference mitigation policies in a few important foreign countries such as United States and Japan. This policy study will be contributed for the future air safety in the aeronautical frequency management point of view.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.3
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• pp.327-331
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• 2010

The 21.4-22.0GHz frequency band is used to broadcast satellite services in Region 1 and Region 3 in frequency distribution area. The use of this frequency band is according to the provision of the resolution 525 of WRC-03, this frequency band broadcasting service system transmits broadband radio-frequency signals. The trend of the Satellite launching plans for an using this frequency band is growing in worldwide. This frequency band requires fairly more transmit power than the Ku-band because of the rain attenuation of this frequency band is very extreme. An appropriable sharing criteria is required for this broadcast service to be operational.

• Standardization Trend in Telecommunications
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• s.24
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• pp.224-232
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• 1992

페이징 시스템의 발달과 시행은 오늘날 특정 영역 내에서의 진보가 다른 영역의 균형있는 발전에 얼마나 많이 의존하고 있는가를 보여주는 전형적인 예이다. 과거의 페이징 시스템은 한 공장의 근로자에게 혜택을 주었다. 위성을 이용하는 미래의 페이징 시스템은 전세계 모든 곳의 모든 사람에게 다양한 혜택을 제공해 줄 수 있게 된다. 점진적으로, 한 쌍의 킬로미터와 점선으로 연결된 전구와 벨은 처음으로 무선시스템으로 대체되어 한 국가라는 지역을 넘어서 서비스를 제공해 왔다. 디지털 기술의 개발을 포함해서, 무선 설비가 소형화 됨에 따라 이러한 일은 점차적으로 이루어져 왔다. 따라서 전기통신에 의한 우주 무선통신과 특히 정지위성 시스템의 엄청난 발전으로 전세계는 가까워지게 되었지만 거의 엄청난 비용과 이용자들이 갖춰야할 것들 때문에 이러한 영역에 접근하는 것은 거의 한정되어 방송용으로만 준비되어 왔다. 오랫동안 LEO 위성은 과학적, 군사적인 용도로만 이용되어 왔는데 그것은 이 위성이 원래 가지고 있는 문제점들로 하루마다 지평선 위의 아주 짧은 통행로와 관계된 것 때문이었다. 그러나 현재는 하나의 시스템을 형성하기 위해 수많은 LEO 위성들의 발사를 감당해 낼 수 있는 장치와 여러 영역에서의 공동작용(synergy) 덕분에, VHF대의 아주 저렴한 시설을 이용한 경제적, 기술적 장점을 인식하고, 혼신을 다하여 다이내믹 채널 활동지점 시스템(denamic channel activity assignment system)을 개발하였고, 마지막으로 말하지만 결코 가볍게 인식해서는 안될 WARC-92가 필요한 주파수대를 지정해야한다는 의도를 밝힌 것 등이 개인간의 통신을 전세계적으로 확대하는데 있어서 디딤돌이 될 것이다.