• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.588-590
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• 2022

Sharing both locations and positions of ships makes it possible to utilize critical item for their safe and efficient navigation in such diversifying meantime environments. AIS is the representative technology for the sharing solutions. The AIS is even used in airspace and ground stations, so that AIS could facilitate the ships' safety navigation and their prevention/rescue from endangers. Due to AIS's many advantages, IMO(International Maritime Organization) made adapting the AIS mandatory for international passenger ships and the ships that are over than 300 tons. AIS uses VHF band areas for transmitting information and the information can be propagated to several hundreds km in range. Due to the large range, AIS monitoring system can acquire huge number of ships, which makes system performance lower and busier. In this paper, we propose the strategy of AIS information extraction for efficient monitoring system. Thus, the monitoring system has higher processing performance and lower network usage. As well as, the proposal affects the monitoring system has more capacity to include other systems' targets, in result.

• Journal of electromagnetic engineering and science
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• v.5 no.2
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• pp.97-103
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• 2005

This paper describes the measured results of sonobuoy transmitting antenna system for anti-submarine warfare (ASW). Since radiation pattern and power density depend on impedance matching between transmitting RF part and antenna with termination resistance, design of matching circuit is very important for sonobuoy system performance. Matching circuit is designed by Smith chart using control of L and C. In standing wave ratio(SWR) measurement using Network Analyzer, SWR of antenna with matching circuit observed 1.5 below at the assigned VHF band. It shows very excellent performance comparison with conversional product that is used for the same object. The measured vertical and horizontal radiation patterns are also shown the satisfaction of military specifications. A drop out of sonobuoy system on the sea is happened when angle of elevation direction is over 10 degrees, and it is conformed that it takes less than I second return to original signal level. The required electric power density is $83\;mW/m^2$ in the military specification, and measured electric power density is observed over average $110\;mW/m^2$ at all frequency bands.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.311-314
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• 2004

A new type of high frequency wideband ultrasonic transducer with a separation between a transmitter and a receiver was proposed and its characteristics were simulated using the PSpice model. The piezoelectric ceramic $PbTiO_{3}$ as a transmitter and the piezoelectric copolymer P(VDF-TrFE) as a receiver were used for high sensitivity and wide bandwidth, respectively. The characteristics of a center frequency approximately 40MHz focusing transducer fabricated in this study showed very wide bandwidth which could give an axial spatial resolution better than 30um in the B-mode image for biological tissues.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.8
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• pp.1-9
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• 1992

Radio data system is a next-generation broadcasting system of digital information communication which multiplexes the digital data into the FM stereo signal in VHF/FM band and provides important and convenient service features. And radio data are composed of groups which are divided into 4 blocks with information word and check word. In this paper, radio data receiver is developed which recovers and process radio data to provide services. Then we confirm that 7dB SNR is required to be 10S0-5TBER of demodulation. Deconding process of shortened-cyclic-decoder has been simulated by computer. Also, the time-compression (by 16 times) method has been adopted for the RDS features post-processing. Via the error probability calculation, simulation and experimentation, the developed receiver system is proved to satisfy the system specification of EBU and implemented by general logic gates and analog circuits.

• Journal of Aerospace System Engineering
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• v.2 no.3
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• pp.33-39
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• 2008

VDL Mode 2 is one of air-to-ground VHF digital data link technologies. The VDL Mode 2 system is designed to be an air-to-ground subnetwork of the Aeronautical Telecommunication Network (ATN) using the AM(R)S band and it is organized according to the Open System Interconnection (OSI) model (defined by ISO). It can be used in ATS Applications especially for ATC communication such as CPDLC and ADS as well. And It is expected VDL Mode 2 replaces ACARS(Aircraft Communications Addressing and Reporting System) which has broadly been used for over 20 years. This paper presents the result of design of operational test equipments for the validation of VDL Mode 2 system under development in KARI.

• Journal of the Korean Institute of Telematics and Electronics
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• v.17 no.6
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• pp.78-85
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• 1980

A symmetrical 3-dB quadrature hybrid circuits, consisting mainly of bifilar pair of taitoted wires, is described. A cascade of two such hybrid circuits can achieve an octave bandwidth hybrid circuit with a small coupling loss. Since the proposed type is simple, compact, and low In cost 1 its applicarion may be preferred to the more common coaxial line or printed -circuit type hybrid version in the frequency region below 1 GHz. This study provides a design method for a hybrid circuit mixing two different antenna signals for the anti - ghosting of television signal.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.6
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• pp.18-25
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• 1994

If a 4-port network is terminated by arbitrary impedances, there are great advantageges in composing systems with it. The distributed 3-dB $O^{\circ}$/180$^{\circ}$ hybrid with the impedances asymmetrically terminated is presented. In the band of UHF and VHF. on the basis of it , the new design method of small sized- hybrid using both lumped and distributed elements is also presented and analyzed At the center frequency of 900MHz. 3-dB $O^{\circ}$/180$^{\circ}$hybrid on the RT/Duroid substrate of ${\varepsilon}_{r}$=2.2, h=0.76mm is design and tested. Agreements are obtained between measured and theoretical results and at the same time the occupied area of it is reduced more than 70% compared with only distributed-type circuits.

• ETRI Journal
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• v.38 no.5
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• pp.879-884
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• 2016

In this paper, an ultra-small marker beacon antenna operated in the VHF-band is proposed. This antenna has a modified linear IFA structure with a lumped capacitor and a capacitive plate for frequency tuning and impedance matching. The capacitive plate is directly connected to the end of a linear radiator and is separated from the antenna ground by 1 mm. The main operating frequency is mainly controlled by the size and dielectric constant of the capacitive plate. The lumped capacitor is useful for fine frequency tuning. Using the proposed structure, an ultra-small marker beacon antenna can be realized with a length of 0.04 ${\lambda}_0$.

• Information and Communications Magazine
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• v.30 no.1
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• pp.47-57
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• 2012

본고에서는 DTV (Digital Television) 서비스로의 전환으로 사용 가능한 TV 화이트 스페이스 (TV White Space; TVWS)의 무선통신 기술규격과 위치정보 기반 TVWS DB (Geo-location based TVWS Database)에 대해 전반적인 내용을 소개하였다. 위치정보 기반 TVWS DB는 TVWS가 존재하는 VHF (Very High Frequency)와 UHF (Ultra High Frequency) 대역에서의 1차 우선 보호 서비스인 지상파 방송 서비스와 소출력 방송 중계기, 무선 마이크에 대한 간섭보호를 보증하며, TVWS를 활용하는 TVBD (TV Band Device)의 위치정보를 기반으로 허용가능 전송전력 및 TVWS 채널할당과 같은 핵심 역할을 수행한다. 본 고에서는 이와 함께 위치정보 기반 TVWS DB에 대한 국내외 연구개발 동향 및 시범 서비스 현황에 대해서도 소개하고자 한다.

• Journal of Advanced Navigation Technology
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• v.11 no.1
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• pp.9-16
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• 2007

In this paper, the Bit Error Ratio (BER) performances of the D8PSK modulation schemes for VDL Mode-2 are analyzed according to the matched and unmatched cases of the channel filters. The carrier frequency and phase offset effects are analyzed with unmatched case. Generally in digital transmission techniques, the Root Raised Cosine filters which are used as channel filters are applied to both sides at transmitter and receiver in order to achieve no ISI, but in VDL Mode-2, the Raised Cosine Filter is used only in transmission section and the receiver section uses general low pass filter, therefore we could not achieve ISI reduction effects but can have better spectrum quality. From the simulation results, the error probability is increased slightly (1~2dB) with use of un-matched channel filter, we got the conclusions that carrier phase offset do not effect to bit error ratio, but the frequency offset effect is so serious. Finally, narrow band D8PSK modulation signals are generated by the use of Digital Up-Converter and then its features are compared with analog modulator.