• Journal of Navigation and Port Research
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• v.30 no.8 s.114
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• pp.637-642
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• 2006

In this paper, we made an experiment on materials of two kinds. First, we made a study of Multi-layer EM wave absorbers using Sendust. In result, The bandwidth of the Multi-layer Sendust EM wave absorbers over 10 dB is extended in S-Band. Second, we investigated the mixing effects of AI(OH)3 on Multi-layer Sendust EM wave Absorbers. In result, the Multi-layer Sendust EM wave absorbers mixed with Al(OH)3 showed a extended bandwidth over 10 dB compared with non-mixed Multi-layer Sendust EM wave absorbers in S-Band.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.297-300
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• 2006

In this paper, the EM wave absorbers were designed and fabricated for X-band sensors using Carbon of dielectric material with CPE. The complex relative permittivity of samples is calculated by the measured S-parameter data. We simulated the double-layered type EM wave absorber with broad bandwidth using the measured complex relative permittivity by changing the thickness and layer, which was fabricated based on the simulated design. The fabricated EM wave absorber consist of 1mm first layer sheet facing metal with Carbon composition ratio 70 vol% and 1.5 mm second layer sheet with Carbon composition ratio 60 vol%. The comparisons of simulated and measured results are good agreement. As a result, the optimized absorption ability of double-layered type EM wave absorber with thickness of 2.5 mm is higher than 10 dB from 7.8 GHz to 13.3 GHz.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.157-161
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• 2006

Generally, a silicone rubber and a chlorinated polyethylene(CPE) have been used as a binder for the development of high-performance composite EM(Electro Magnetic) wave absorbers. In this paper, the EM wave absorption performance of natural lacquer, which is newly proposed as a binder was investigated. The prepared MnZn ferrite EM wave absorbers are mixed with natural lacquer showed excellent EM wave absorption characteristics compared with MnZn ferrite EM wave absorbers which are mixed with the conventional binders. MnZn ferrite EM wave absorbers mixed with natural lacquer were prepared and their absorption ability was also investigated. The EM wave absorbers are fabricated in different proportions of MnZn, or NiZn ferrite and natural lacquer, and their reflection coefficients are measured. The permittivity and permeability are calculated by using the measured reflection coefficients. The EM wave absorption abilities are calculated according to different thicknesses of the EM wave absorbers.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.97-101
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• 2006

In this paper, Multi-layer EM wave absorbers using Sendust are presented. The bandwidth of the Multi-layer Sendust EM wave absorbers over 10 dB is extended in S-Band And we investigated the mixing effects of $Al(OH)_3$ on Multi-layer Sendust EM wave Absorbers. As a result, the Multi-layer Sendust EM wave absorbers mixed with $Al(OH)_3$ showed a extended bandwidth over 10 dB compared with non-mixed Multi-layer Sendust EM wave absorbers in S-Band.

• Journal of Advanced Navigation Technology
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• v.6 no.4
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• pp.318-325
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• 2002

In this paper, the effects of the interference environments on the performance of the time hopping(TH) binary PPM impulse radio(IR) system are presented. Based on the monocycle pulse available within the frequency of 3.1~10.6 GHz permitted for application by FCC, a PPM-modulated TH IR system simulator was designed and followed by the analysis of the monocycle pulse characteristics as well as the system performance. Particularly for the evaluation of the system performance, the multiple access interference and the narrowband system interference signals were considered as the interference signals. Since the narrowband system interference signal has very narrow bandwidth and very large amplitude compared with those of IR system, the analysis of the IR system performance was implemented by considering the interference power and band fraction ratio of the narrowband interference signal.

• Journal of Advanced Navigation Technology
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• v.8 no.2
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• pp.91-97
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• 2004

This paper presents the development of InGaAsP multiple quantum well asymmetric Fabry-Perot modulators(AFPM), which have a vertical structure and high performance and describes measurements of devices operating at 10GHz for next generation broadband wireless communication applications such as picocell systems. Advantages of the AFPM include low drive voltage, which is less than -2V, and -3dB coupling loss, good flatness of the frequency response and simple fiber alignment. A simple link demonstration has been introduced, resulting in 92dB/Hz spurious free dynamic range and 40dB inter-modulation distortion. This modulator could be use for broadband radio over fiber systems such as picocell and multiple RF links.

• Journal of Advanced Navigation Technology
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• v.17 no.5
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• pp.506-515
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• 2013

In cognitive radio networks, several research works typically address the framework which consists of a spectrum sensing period and a data transmission period. When the frame period is short, there is the problem that the throughput of secondary users decrease. In this paper, aggregated data slot structure is considered to increase the throughput of secondary users. Chapman-Kolmogorov equation is used for the modeling of the transmission probability of primary users and formulation of an optimization problem to maximize the throughput of secondary users. Solution of the optimization problem results in the optimal spectrum sensing time, the length of data slot and the number of data slots governed by a spectrum sensing.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.11a
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• pp.390-391
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• 2022

Recently, SpaceX, private enterprise dealing in space development company, has reported a plan for launching of low earth orbit satellites via Starlink Business, and launched 900 satellites until now. Concretely, it plans tp operate Ku/Ka band satellite, and launch 7,518 of V band satellites for broadband communication. Therefore, wireless communication service for ship will be provided, and various solutions will be offered through the low earth orbit satellites. In this work, we investigated RF characteristics of coplanar waveguide employing periodic 3D coupling structures, and examined its potential for a development of marine radio communication FISoC (fully-integrated system on chip) semiconductor device.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.159-160
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• 2010

In this paper, we compared the absorption abilities of AMP and Sendust EM wave absorbers for a port logistics RFID system. Firstly, we fabricated EM wave absorber samples by using each absorbing material, AMP or Sendust, and CPE (Chlorinated Polyethylene) with composition ratios 85 : 15 wt. %. Secondly, we designed the optimum EM wave absorber using the calculated material constants found from the measured input impedance of the samples. Therefore, we confirmed that imaginary factor of complex relative permeability influences absorption ability and that AMP is better absorbing material than Sendust at the frequency band of 433 MHz.

• Journal of Advanced Navigation Technology
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• v.14 no.1
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• pp.33-40
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• 2010

In this paper, the bit-error-ratio (BER) performances of Digital Radio Mondiale Plus (DRM+) system which stand for the European standard to bring analogue FM radio to digital radio in Band-II(30-170 MHz) are evaluated under multipath fading channel models used in Band-II and the adjacent channel interference (ACI) caused by FM signal. From the simulation results, the DRM+ system shows robust performances under time-varying channel environments even though the speed of a vehicle is equal to 300km/h. And it is shown that the frequency diversity, determined by delay spread of multipath fading channel, increases the coding gain of the DRM+ system with an increase of delay spread. In addition, to guarantee the BER performance of 10-4 for DRM+ system with ACI due to FM signal, the simulation results show that the desired signal-to-ACI power ratio must be more than -30 dB when the carrier frequency distance is 150 kHz.