• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.4
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• pp.1458-1470
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• 2018

In this letter, a new dual-port Multiple-Input Multiple-Output (MIMO) antenna is introduced which has two independent signal feeding ports in a single antenna element to achieve smaller antenna volumes for the 5G mobile applications. The dual-port structure is implemented by adding a cross coupled semi-loop (CCSL) antenna as the secondary radiator to the ground short of inverted-F antenna (IFA). It is found that the port to port isolation is not deteriorated when an IFA and CCSL is combined to form a dual-port structure. The isolation property of the proposed antenna is compared with a polarization diversity based dual-port antenna proposed in the literature [9]. The operating frequency range is 3.3-4.0 GHz which is suitable for places where $4{\times}4$ MIMO systems are supposed to be deployed such as in China, EU, Korea and Japan at the band ${\times}$ (3.3 - 3.8GHz. The measured 6-dB impedance bandwidths of the proposed antennas are larger than 700 MHz with isolation between the feeding ports higher than 18 dB [1-2]. The simulation and measurement results show that the proposed antenna concept is a very promising alternative for 5G mobile applications.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.664-667
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• 2010

Solid rocket propulsion systems are generally used for tactical missiles due to the structural and operational simplicity. Nevertheless, various kinds of design factors including outer diameter, length, weight, loading efficiency of propellant grain effects to thrust performance. Dual thrust is beneficial to range extension and terminal velocity increasement. But loading efficiency becomes low in case to obtain dual thrust performance by burning surface control. So, It is predicted to be reasonable to obtain dual thrust performance with high/low burning rate propellants. This study is on internal ballistic analysis and ground test to confirm dual thrust performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.11
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• pp.951-959
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• 2015

Ground radiation antenna in mobile devices is becoming an issue for satisfying both miniaturization and high performance. Ground radiation antenna controls the characteristic mode of the ground plane and couples this mode with the ground radiation antenna, thereby having good radiation performance. In this paper, the characteristic mode theory and applications of ground radiation antenna will be introduced. The operating mechanism of single band, wideband and dual-band ground radiation antennas are studied.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.746-749
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• 2002

This paper is introducing a radio control helicopter as a new platform of ground truth measurement. This helicopter is normally used for spraying an agricultural chemical. It can do pinpoint hovering and programing flight using DGPS etc., A spectrometer with dual port can measure ground surface and white reference plate at the same time. And it can also take digital images by digital camera. It is needed to collect ground reflectance information as satellite sensor footprint size for satellite data validation. Generally it is possible to get such ground reflectance by an airplane measurement. But it is high cost and not so easy to make a measurement by airplane. Developed validation system can provide such ground reflectance in low cost and easy.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.3
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• pp.445-450
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• 2015

Generally, Low Earth Orbit (LEO) satellites are used to collect image or video from earth's surface. The collected data are stored on-board and/or transmitted to the main ground station directly or via polar ground station using terrestrial line. Today, an intersatellite link between a LEO and a GEO satellite allows transmission of the collected data to the main ground station through the GEO satellite. In this study, an approach for a continuous communication starting from LEO through GEO to ground station is proposed by determining the optimum ground station locations. In doing so, diverse ground stations help to determine the GEO orbit as well. Cross-correlation of the long term daily rainfall averages are multiplied with the logarithmic correlation of the sites to calculate the joint correlation of the diverse ground station locations. The minimum values of this joint correlation yield the optimum locations of the ground stations for Q/V-band communication and satellite control operations. Results for several case studies are listed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.10 s.113
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• pp.959-966
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• 2006

This paper proposes a new concept about dual band predistortion linear power amplifier(PD LPA) using diplexer for digital cellular ($f_o$=880 MHz) and IMT-2000($f_o$=2,140 MHz) base stations. The diplexer is composed of low pass filter having defected ground structure(BGS) microstrip line and high pass filter having high-Q lumped capacitors and distributed elements. The proposed predistorter adopts a reflection type intermodulation signal generator with 3 dB hybrid coupler for good reflection characteristic. for a forward link one carrier CDMA IS-95A 1FA and WCDMA 1FA signal, the proposed dual band PD LPA shows the adjacent channel leakage ratio(ACLR) improvement about 10 dB and 9.36 dB for digital cellular and IMT-2000 band, respectively.

• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.211-218
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• 2007

Dual-polarization means to use two orthogonal polarizations, namely two independent channels in communication. This can be used to deal with high datarate caused by large amount of observed data in future LEO satellite. However, when two orthogonal polarizations are not perfectly independent to each other in practical, interference is probably raised in each channel, meaning that noise level in passband increases. XPD (Cross-Polarization Discrimination) is the ratio of the signal level at the output of a receiving antenna that is nominally co-polarized to the transmitting antenna to the output of a receiving antenna of the same gain but nominally orthogonal polarized to the transmitting antenna. In this paper, the influence of XPD on the communication between satellite and ground station was analyzed under the assumption that X-Band dual-polarization was applied to KOMPSAT-2 (KOrea Multi-Purpose SATellite-2). Through analysis, it was shown that more than 3dB of link margin was still achievable despite of worst axial ratio, 2.5dB, at ground station antenna when axial ratio of satellite antenna was about 0.5dB under 99% of environmental availability.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.254-257
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• 2003

본 논문에서는 휴대폰에 사용되는 Multi-band 용 helical antenna 의 radiation pattern 을 체적화하기 위한 방법을 제안하고자 하였다. 일반적으로 GSM 휴대폰에 사용되는 안테나는 GSM, DCS 의 dual band 인 경우가 다수이며 추세에 따라 요즘은 PCS 등을 포함한 triple band 의 안테나가 많이 선호되고 있다. 이러한 multi band antenna 의 radiation pattern 에 영향을 미치는 변수로 본 논문에서는 ground 의 length 와 width 그리고 폴더쪽에 사용되는 LCD 의 ground 와 폴더쪽 기구물에 사용된 EMI spray 등의 변화를 통해 pattern 의 변화를 알아보고 이러한 변수를 조절하여 radiation pattern을 최적화하는 방법에 관하여 논하였다.

• Bulletin of the Korean Chemical Society
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• v.12 no.4
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• pp.441-444
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• 1991

The intramolecular proton transfers of 2-hydroxy-4,5-naphthotropone in room temperature solutions are studied using static and time-resolved absorption and emission spectroscopy. Dual normal and tautomer fluorescence is observed in ethanol solution, while only the tautomer fluorescence is observed in cyclohexane solution. The fluorescence lifetimes and quantum yields in ethanol and cyclohexane solutions indicate that in hydrocarbon solvents, rapid intersystem crossing competes with proton transfer in the first excited singlet state. Transient absorption spectra and kinetics indicate that proton transfer also undergoes in the first triplet state with a transfer time of ∼ 3 ns. No transient absorption from the tautomer ground state indicates a rapid back proton transfer in the ground state.

• ETRI Journal
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• v.35 no.3
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• pp.530-533
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• 2013

In this letter, a simple method for reducing the size of a dual-band planar inverted-F antenna (PIFA) is described. This method is based on a coupling capacitor connected in parallel to the PIFA feed conductor. The proposed antenna occupies a small ground clearance of $10mm{\times}5mm$ and is able to provide -10-dB impedance bandwidths of 120 MHz and 760 MHz for 2.45-GHz and 5.5-GHz wireless local area network applications, respectively. The measured antenna efficiencies are 71.8% and 73.6%, averaged over the 2.45-GHz and 5.5-GHz frequency bands, respectively.