• Journal of Navigation and Port Research
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• v.31 no.6
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• pp.503-507
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• 2007

In this paper, the ultra-widebend, microstrip patch antenna with the bandwidth of 3 GHz was implemented for ultra-wideband(UWB) wireless communication applications. In order to cover the very wide bandwidth of 3 GHz, a multi-resonance antenna was designed, each resonance frequency was separated into five frequency bend, 7.5, 8.1, 8.7, 9.3, and 9.9GHz with the interval of 600MHz BW. And for wideband characteristics of each antenna, U-slot antennas were designed at each center frequency. Designed five U-slot antennas were connected in series for multi-resonance of 3GHz BW and wideband matching was also designed for impedance matching transmission line calculated. The relative dielectric constant, the height, the loss tangent of the PCB substrate were ${\epsilon}_r=4.8,\;h=0.6$ and loss tangent=0.0009 respectively. The implemented antenna's radiation patterns and gain were directivity characteristics and $1.46{\sim}4.08dBi$ at the five separated center frequency.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.9
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• pp.16-23
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• 2009

In this paper, we propose a new distributed Alamouti space-time block coding scheme using cooperative relay system composed of one source node, three relay nodes and one destination node. The source node is assumed to be equipped with two antennas which respectively use a 2-beam array to communicate with two nodes selected from the three relay nodes. During the first time slot, the two signals which respectively were transmitted by one antenna at the source, are selected by one relay node, added, amplified, and forwarded to the destination. During the second time slot, the other two relay nodes implement the conjugate and minusconjugate operations to the two received signals, respectively, each in turn is amplified and forwarded to the destination node. This transmission scheme represents a new distributed Alamouti space-time block code that can be constructed at the relay-destination channel. Through an equivalent matrix expression of symbols, we analyze the performance of this proposed space-time block code in terms of the chernoff upper bound pairwise error probability (PEP). In addition, we evaluate the effect of the coefficient $\alpha$ ($0{\leq}{\alpha}{\leq}1$) determined by power allocation between the two antennas at the source on the received signal performance. Through computer simulation, we show that the received signals at the three relays have same variance only when the value of $\alpha$ is equal to $\frac{2}{3}$, as a consequence, a better performance is obtained at the destination. These analysis results show that the proposed scheme outperforms conventional proposed schemes in terms of diversity gain, PEP and the complexity of relay nodes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.4
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• pp.515-525
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• 1998

In this paper, for both transmission and reception with single antenna system of satellite communication, dual-frequency antennas which operate simultaneously at 12.5 GHz and at 14.25 GHz are designed, constructed and measured. Also by using dual feeding structure, the problems of single-fed dual-frequency antenna such as the separation of transmitting and receiving signals and single polarization, are solved. Microstrip patch as a radiation element of dual-fed dual-frequency antenna has width and length which are the resonance lengths of the corresponding frequencies for transmission and reception, respectively. The effects of the feed line on the other frequency feeding are minimized with the optimal matching scheme for the feed lines. For solving the space problems of dual-fed two-dimensional array antennas, microstrip-line and coaxial probe feedings are used for each frequency and a two-dimensional $2\times2$ array antenna was designed and measured their characteristics. The experimental results show that errors of resonance frequencies are less than 1.44%, the return losses are less than -21 dB and the isolations between two feeding ports are less than -21 dB. The characteristics of radiation patterns of dual frequency microstrip antenna are measured and evaluated. The directivities, sidelobe levels and cross polarizations are also measured and compared with the simulations. The results show some errors due to the misalignment of coaxial probe feeding.

• Journal of Advanced Navigation Technology
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• v.19 no.1
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• pp.60-65
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• 2015

In the present study, compact $0^{th}$ order resonant antenna for 2.4 GHz ISM frequency band is newly proposed. In case of wireless communication systems such as wi-fi, bluetooth and Zigbee, antennas with omni-directional radiation pattern are necessary because of the demands for uniformly received electric field strength without variation for direction. It is well-known that $0^{th}$ order resonant antennas are not only advantageous for miniaturization but also have advantage of maintaining omni-directional radiation pattern. The proposed antenna is composed of two-element array in which the size of unit element should be smaller than ${\lambda}/4$ correspondent to the resonant length of typical monopole antennas The proposed antenna which is placed at middle and upper side of PCB with $50{\times}50mm^2$ size is designed and fabricated within limited space of $8{\times}5mm^2$. The measured impedance bandwidth ($S_{11}{\leq}-10dB$) is about 100 MHz (2.4~2.5 GHz) which corresponds to quite wide bandwidth in comparison with the antenna size, and also the measured peak gain over the passband is more than 3 dBi which is thought to be slightly wider than the other $0^{th}$ order resonant antenna.

• Journal of Biosystems Engineering
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• v.25 no.2
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• pp.97-106
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• 2000

To develop the grain moisture meter using microwave free space transmission technique, a 10.5GHz microwave signal with the power of 11mW generated by an oscillar with a dielectric resonator is transmitted to an isolator and radiated from a transmitting $2{\times}2$ microstrip patch array antenna into the sample holder filled with the 12 to 26%w.b. of Korean Hwawung paddy rice. the microwave signal, attenuated through the grain with moisture, is collected by a receiving $2{\times}2$ microstrip patch array antenna and detected using a Shottky diode with excellent high frequency characteristic. A pair of light and simple microstrip patch array antenna for measurement of grain moisture content is designed and implemented on atenflon substrate with trleative dielectric constant of 2.6 and thickness of 0.54 by using Ensemble ver. 4.02 software. The aperture of microstrip patch arrays is 41 mm width and 24mm high. The characteristics of microstrip patch antenna such as grain. return loss, and bandwidth are 11.35dBi, -38dB and 0.35GHz($50^{\circ}$ at far-field pattern of E and H plane. The width of the sample holder is large enough to cover the signal between the antennas temperature and bulk density respectively. The calibration model for measurement of grain moisture content is proposed to reduce the effects of fluectuations in bulk density and temperature which give serious errors for the measurements . From the results of regression analysis using the statistically analysis method, the moisture content of grain samples (MC(%)) is expressed in terms of the output voltage(v), temperature (t), and bulk density of samples(${\rho}b$)as follows ;$$MC(%)\;=\;(-3.9838{\times}10^{-8}{\times}v^{3}+8.023{\times}10^{-6}{\times}v^{2}-0.0011{\times}v-0.0004{\times}t+0.1706){\frac{1}{{\rho}b}}{\times}100$ Its determination coefficient, standard error of prediction(SEP) and bias were found to be 0.9855, 0.479%w.b. and -0.0.369 %w.b. respectively between measured and predicted moisture contents of the grain samples.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3A
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• pp.111-118
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• 2003

The transmit adaptive array requires the forward link channel information for evaluating the optimum transmit weight vector in which a feedback channel provides transmitter with the forward link channel information. The larger transmit adaptive array is, the higher required rate of feedback channel is. Therefore we consider the system that the N-transmit antenna system is expanded to the 2N-transmit antenna system, while the feedback channel is maintained as that of N-transmit antenna system. The increase of the number of antennas can produce the additional diversity gain, however the insufficient feedback bits assigned to each antenna aggravates the quantization error. In this paper, we propose the transmit antenna selection in order to improve the performance of transmit adaptive array having an insufficient feedback channel information. The effective method to transmit the weight vector is also introduced. System performances are investigated for the case of N=4 corresponding to the antenna selection diversity schemes on the flat fading channel and the multipath fading channel. The simulation results show that the proposed scheme can improve the system performance by 1 dB when the N is expanded to the 2N, while the feedback channel is restricted to that of N-transmit antenna system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.8 s.99
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• pp.803-809
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• 2005

This paper presents a novel method of mutual coupling suppression between antenna elements for performance improvement in planar array antenna system. Two miniature patch antenna elements satisfied IEEE 802.1 la($5.75\~5.35\;GHz,\;5.75\~5.85\;GHz$) are used for this research, they are arrayed by half wave length interval. It is observed about -20 dB mutual coupling between each antenna element at center frequency. To suppress mutual coupling, the arrayed antennas with a reversed 'U' structure are observed below -30 dB mutual coupling at IEEE 802.1la band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.8
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• pp.576-582
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• 2018

In this paper, a planar equi-phase power divider is proposed using fixed phase shifters. As the integrability of a phased array antenna increases for accurate beam steering, a conventional method to excite equi-phase signals to all element antennas, extending the feedline, has spatial limitations. Therefore, the planar equi-phase power divider is designed using a defected ground structure with a planar phase shift function without intentional feedline extension. The defected ground structure has been considered for a low insertion loss and a controllable phase shift, whereas the power divider has been designed and implemented with a port-to-port isolation and a planar configuration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.12
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• pp.1061-1068
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• 2013

In this paper, we propose a $M{\times}M$ beam-space multiple input multiple output (BS-MIMO) system using electronically steerable parasitic array radiator (ESPAR) antenna. Conventional MIMO method required multiple RF chains because it map the transmission signals onto multiple antennas. So, conventional MIMO system has high cost for design and high energy consumption at RF circuit. Also, It is difficult to use MIMO system in battery based mobile terminals with limited physical area. In order to solve these problems, BS-MIMO technique which map the data signal onto bases in beam space domain was proposed using ESPAR antenna with single RF chain. This paper, we design and analyze the performance of extended $M{\times}M$ BS-MIMO technique. Simulation results show that the proposed BS-MIMO system has similar BER performance compare to conventional MIMO scheme. Therefore, BS-MIMO system with single RF chain will has a low RF power consumption and low cost for RF hardware design as compared with conventional MIMO technique with multiple RF chains.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.53-58
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• 2007

The Satellite Mobile Communication System holds several advantages, such as wide coverage that guarantees the communication in a huge area. It is suitable in the ocean and forest and especially in emergency situation. However, the licensed frequency is not always occupied within all coverage and all the time. The actual utilization rate is relatively low compared to other wireless communications such as cellular systems. There are a large amount of white spaces in its coverage. Therefore, it is necessary to consider introducing additional services such as data communication, in order to increase the spectrum utilization as well as the revenue of the Satellite service provider. In this paper, we first analyze the possibility to implement new services in the licensed band of satellite mobile phone by its provider. Then we address the most significant issue for the implementation of current service, which is how to accurately detect the satellite mobile terminals. Finally, we suggest two new possible solutions namely, eigenvalue detection based methods to find out the existence of transmitted signal from the satellite mobile terminals.