• Journal of Navigation and Port Research
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• v.45 no.5
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• pp.231-237
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• 2021

Enhancing the performance of maritime wireless communication has been highlighted by the issue of cell planning in the sea area because of lack of an appropriate Propagation Loss Model (PLM). To resolve the cell planning issue in vast sea areas, it was essential to develop the (PLM) matching the intended sea area. However, there were considerable gaps between the prediction of legacy PLMs and field measurement in propagation loss and there was a need to develop the adjusted PLM (A-PLM). Therefore, cell planning was performed on this adjusted model, including modification of the base station's location, altitude, and antenna azimuth to meet the quality objectives. Furthermore, in order to verify the availability of the cell planning, Communication Service Quality Monitoring System (CS-QMS) was developed in the LTE-Maritime project to collect LTE signal quality information from the onboard equipment at regular intervals and to ensure that the service quality was high enough to satisfy the goals in each designated grid. As a result of verification, the success rate of RSRP was 95.7% for the intensive management zone (IMZ) and 96.4% for the interested zone (IZ), respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.426-435
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• 2013

In this paper, we propose the MIMO circular polarization feed network to enhance the communication performances from the previous $2{\times}2$ MIMO channel to $4{\times}4$ channel for Land Mobile Satellite communication system. The only possibility to extend the communication channel is to use the additional satellite because of the limitation of satellite spaces to install additional antennas. For overcoming this problems, we propose the MIMO circular polarization feed network to secure the isolation characteristics without the distant antenna space. The port isolation characteristics and each port impedance matching conditions are numerically verified and we suggest the $4{\times}4$ MIMO channel model of the proposed system and the performances are verified. The fabricated circular polarization patch antennas with the proposed feed network are measured in the reverberation chamber and 7~10 dB of diversity gain and 80 % increasement of channel capacity are obtained.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.397-401
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• 2005

In this paper, we have developed a frequency mixer which can be used as a microwave phase conjugator in the retrodirective array antenna. The retrodirective array, which can reflect the incident wave retrodirertively back to the source direction without any priori information, requires phase conjugators to achieve the phase change of 180 degrees for the incoming signal. frequency mixers can efficiently serve as phase conjugators. The circuit topology is of the 2-port structure to avoid the complexity of LO and Rf signal combination and matching circuits, using a pseudomorphic HEU device. The operating frequencies are 4.0 CHz, 2.01 CHz, and 1.99 CHz for LO, RF, and If signals, respectively. Conversion loss is measured to be -ldB and 1-dB compression point -l5 dBm at the LO power of -10 dBm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.134-138
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• 2005

In this paper, we have developed a new type of the microwave phase conjugator for the active retrodirective antenna array. The circuit topology is consisted of a 2-port structure to avoid the complexity of LO and RF signal combination and matching, using the cascade connection of two single-ended mixers. The operating frequencies are 4.0 GHz, 2.01 GHz and 1.99 GHz for LO, RF, and IF, respectively. Conversion loss is measured to be -7 dB and 1-dB compression point 15 dBm with the LO power of 9 dBm. For the most important parameter, the isolation between RE leakage and IF signal is as high as 25 dB.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.239-244
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• 2004

In this paper, we have developed a frequency mixer which can be used as a microwave phase conjugator in the LS band retrodirective antenna system. The mixer as a phase conjugator must have an If signal of which frequency is nearly as high as that of an RF signal, so this fact brings difficulty in the combination of input signals and the design of impedance matching circuit. The circuit configuration is chosen to be of the gate mixer using a pseudomorphic HEMT device. The operating frequencies are 4.00 ㎓, 2.01 ㎓, and 1.99 ㎓ for LO, RF, and IF, respectively. Conversion gain is measured to be 12.5 ㏈ and 1 ㏈ compression point -34 ㏈m at the LO power of -7 ㏈m. The mixer fabricated in this research is the single-ended type, where RF leakage signal appears inevitably at the If port because RF and If frequencies are almost the same. The circuit topology suggested here can be applied directly to the design of balanced-type mixers and phase conjugators.