• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.746-752
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• 2009

In this paper, we deal with the development of an optimal design program for a triple-band PTFA(Planar Inverted-F Antenna) of 433 MHz, 912 MHz and 2.45 GHz by using evolution strategy. Generally, the resonance frequency of the PIFA is determined by the width and length of a U-type slot used. However the resonance frequencies of the multiple U slots are varied by the mutual effect of the slots. Thus the optimal width and length of U-type slots are determined by using an optimal design program based on the evolution strategy. To achieve this, an interface program between a commercial EM analysis tool and the optimal design program is constructed for implementing the evolution strategy technique that seeks a global optimum of the objective function through the iterative design process consisting of variation and reproduction. The resonance frequencies of the triple-band PIFA yielded by the optimal design program are 430 MHz, 910.5 MHz and 2.458 GHz that show a good agreement to the design target values.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.10
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• pp.934-940
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• 2011

A novel reconfigurable beam steering antenna using double loops is proposed. The double loop antenna has a superposed beam which is produced by combining the in-phase beam in the inner loop with the out-of-phase beam in the outer loop. Also, the doble loop antenna uses two artificial switches to connect between inner loop and outer loop, and has the beam directions of three separate cases(Case 1, Case 2, Case 3) by changing ON/OFF states of switches. The operation frequency of the antenna is 14.5 GHz, and three maximum beam directions of the antenna are ${\phi}_{max}=0^{\circ}$, ${\theta}_{max}=0^{\circ}$(Case 1), ${\phi}_{max}=230^{\circ}$, ${\theta}_{max}=40^{\circ}$(Case 2) and ${\phi}_{max}=130^{\circ}$, ${\theta}_{max}=40^{\circ}$ (Case 3). The peak gains of each case are 6.5 dBi(Case 1), 7.6 dBi(Case 2) and 7.8 dBi(Case 3). The half power beam width(HPBW) of each case is $86{\sim}104^{\circ}$, and the overall HPBW is $160^{\circ}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.10
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• pp.1071-1078
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• 2003

In this paper, the planar, compact, and broadband phased array antenna system for IMT-2000 applications has been investigated. Two methods far designing a low-cost and low-complex beam-farming network are proposed. First, a new compact and broadband phase shifter with continuously controlled phase bits is designed by using parallel coupled lines. Second, its equivalent phase delay line is suggested to be capable of replacing the complex phase shifter with a reference phase bit on a phased array antenna. For the purpose of achieving the broadband system, in addition to the broadband phase shifter, a wide-slot antenna with a ground reflector is utilized as an element antenna. Therefore, the phased array antenna system has achieved compact size, broad bandwidth, and wide steering angle, although it has low complexity and low fabrication cost. The 3${\times}$1 phased array antenna system has a compact size of 1.6 λ${\times}$ l.6 λ, which is the sufficient ground plane of the wide-slot antenna. Experimental results present that the S$\_$11/ has less than 15 dB within the band and its radiation patterns on an E-plane have the capability of steering an antenna beam from -29$^{\circ}$to +30$^{\circ}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.9 s.100
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• pp.932-940
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• 2005

In this paper, a planar half-circle shape ultra-wideband(UWB) antenna fed by CPW is designed, fabricated and measured for UWB communications. Within the UWB band(3.1 GHz${\~}$10.6 GHz), 5.15 GHz${\~}$5.825 GHz frequency band is used by IEEE 802.1la WLAN applications. It may be necessary to notch out this band to avoid interference with IEEE 802.1la WLAN. Therefore, we have proposed three kinds of UWB antennas having a notch function, such as a rectangular slot, a hat-shaped slot a circle-shaped slot. The notch frequency of the proposed antenna can be adjusted by controlling the slot length or slot width. From the measured results, the proposed antennas show a good gain flatness except the IEEE 802.1la WLAN frequency band and have a reasonable agreement with simulated results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.3
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• pp.195-201
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• 2019

The effectiveness of the phased array antenna in wireless power transfer systems is due to its ability to form a beam pattern towards the desired direction. To maximize the efficiency of wireless power transfer through beamforming, the transmitter must recognize the information on the optimal transmission path. To achieve this, the transmitter usually transmits pilot signals periodically and the receiver extracts the optimal beamforming weights using the pilot signals. The receiver then feeds the beamforming weights back to the transmitter. In general, the amount of feedback increases with the number of antennas, which causes feedback overhead when there is a large number of antennas. In this paper, we propose a feedback simplification scheme based on the far-field approximation method. The simulation results are provided to validate the impact of the simplified feedback on the beam pattern.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.11
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• pp.8-16
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• 2000

In this paper, on calculating SARs on human head using computer simulation, SARs caused by PCS handsets are calculated and compared, and the design parameters that affect SAR values are analyzed. Is and 10 g peak averaged SARs are calculated as the type of antenna, the location of antenna, and the type of handset are changed and SAR distributions as depth of human head are shown. Among the antennas on flip type handsets, side mounted PIFA has the lowest SARs 1g and 10g peak averaged SARs are 0.686W/kg and 0.353W/kg. The SARs caused by monopole antenna on folder type handset are 1.133W/kg and 0.709W/kg. and are about 30% lower than monopole 1.759W/kg and 0.978W/kg, respectively. SAR distributions as depth of human head of side mounted PIFA and monopole antenna on folder-type handset are more slowly changed than those of top mounted PIFA and monopole antenna on flip-type handset.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.10
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• pp.4759-4780
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• 2017

Full Dimension multiple input multiple output (FD-MIMO) architecture employs a planar array design at the Base Station (BS) to provide high order multi-user MIMO (MU-MIMO) via simultaneous data transmission to large number of users. With FD-MIMO, the BS can also adjust the beam direction in both elevation and azimuth direction to concentrate the energy on the user of interests while minimizing the interference leakage to co-scheduled users in the same cell or users in the neighboring cells. In a typical highly populated macrocell environment, modelling the elevation angular characteristics of three-dimensional (3D) channel is critical to understanding the performance limits of the FD-MIMO system. In this paper, we study the throughput performance of FD-MIMO system with varying elevation angular spread and inter-element spacing using a 3D spatial channel model. Our results show that for a typical urban scenario, horizontal beamforming with correlated antenna spacing achieves optimal performance but by restricting the spread of elevation angles of departure, elevation beamforming achieves high array gain with wide inter-element spacing. We also realize significant gains due to spatial array processing via modelling the elevation domain and varying the inter-element spacing for both the transmitter and receiver.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.2
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• pp.73-82
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• 2003

For measurements and analysis of dielectric characteristics of planar slabs of microwave absorbing materials, I have applied a free-space method in the frequency range of 8~14 GHz. The measurement system for free-space method consists of transmit and receive antennas, mode transitions, precision coaxal cables, the network analyzer, and a computer Special Spot-focused horn lens antenna was used to eliminate diffraction effects. Diffraction effects at the edges of the sample are minimized by satisfying the condition for minimum transverse dimension of the plate and the beamwidth of the antennas at the focus. The time-domain gating feature of the network analyzer and the thru, reflect, and line(TRL) calibration technique were used to eliminate the effects of undesirable multiple reflections. The complex coefficients of reflection and transmission, $S_{11}$ and $S_{21}$, of planar samples were measured for standard materials such as Teflon, Rexolite$\textregistered$ 2200. The results were compared with existing measurement method. And I applied a free-space method for measurement to measure dielectric constants of some electromagnetic absorbing materials. Dielectric properties for the same samples were also measured with a 7mm coxial transmission line method for purposes of comparison with the free-space method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.1
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• pp.42-49
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• 2018

In this paper, a dual-band microstrip-fed monopole antenna with a DGS(defected ground structure) for WLAN(wireless local area network) applications is presented. The antenna consists of a monopole and a defected ground, which were etched on both sides of the FR-4 substrate. The defected ground structure was used to obtain the dual band, while the step-by-step reduction in the monopole width was used to improve the impedance matching of the antenna. The antenna has an overall compact size of $44{\times}51{\times}1.6mm^3$, which was optimized by varying the size of the monopole and the ground plane such that it may resonate at the 2.4 GHz and 5 GHz bands of the WLAN. The measurement results showed that the antenna operates in the frequency band of 210 MHz(2.29~2.50 GHz) and 900 MHz(5.05~5.95 GHz) for a VSWR under 2, and showed omnidirectional radiation pattern at all desired frequencies.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.7
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• pp.52-60
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• 2009

In this pater, a CP-DRA(Circularly Polarized Dielectric Resonator Antenna) using cross-slot-feed is studied to enhance the gain and axial ratio bandwidth. First, a single layer CP-DRA is studied as a reference for comparison. Then a new type of multilayer CP-DRA is proposed to enhance the gain and axial ratio bandwidth. In consideration of the antenna gain enhancement, the spacing between the elements of the multilayer CP-DRA is examined through analysis of the radiation performance of a 2$\times$2 planar amy of DRAs with a spacing of 0.7$\lambda_0$ and 1.2$\lambda_0$ using CST Microwave Studio. The measured result shows that the gain and bandwidth of the multilayer structure is approximately twice that of the single layer one. In the case of the array antenna in which the spacing between multilayer CP-DRA element is 1.2$\lambda_0$, a grating lobe is reduced, in contrast to what we can expect from a conventional antenna array. The gain is 13.4dBi and axial ratio bandwidth is 0.8GHz.