• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.11
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• pp.44-51
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• 1996

The radiation characteristics of a slot antenna in a plane conductor covered with a miving isotropic plasma layer are analyzed. The radiation null which causes distortion in radiation pattern is explainted by the zero of integrand in an asymptotic integral for radiation fields as a function of the plasma parameter and the plasma velocity. Numerical resutls for a radiation null calculated from various plasma and velocity parameters correspond to the results of two-dimensional problem.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.2
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• pp.57-62
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• 2009

In this paper, we proposed the metal tag antenna of PIFA structure with an isotropic radiation pattern when tag attached the metal material. The antenna consist of antenna body, horizontal patch and ground, and inserted a substrate with high dielectric constant between the antenna body and ground in order to miniaturize the antenna size. The antenna body with symmetric structure is designed to produce an oppositely directed currents. The simulation shows the impedance bandwidth has 20 MHz (900 ~ 920 MHz) and the maximum radiation gain satisfy the -10 dBi and -15 dBi when the tag is in air and attach the metal material. Also, the proposed antenna operates with an isotropic radiation pattern due to satisfy the gain deviation lower than 6 dB, respectively.

• Journal of the Korea Society of Computer and Information
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• v.8 no.1
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• pp.90-96
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• 2003

In this paper, arranged the isotropic point source of N number with the structure which is identical with the receive area. And against the array structure which has the radiation pattern which is identical with the receive area it researched. The arranged the element space flees grating lobe and in order to set the characteristic of optimum with half-wave equally space it selects. After inducing the array factor of each array structure, it calculated a radiation pattern. As a result of, the radiation pattern of the each Planar array antenna with structure of the receive area was similar and the possibility of getting an beam characteristic it was.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.10
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• pp.1089-1095
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• 2003

In this paper, the 26 GHz band omnidirectional antenna that produces an isotropic radiation pattern in the azimuth plane and a directive radiation pattern in the elevation plane was designed by using reflector antennas. To investigate the reliability of the designed antenna, that was analyzed by using the aperture field method and the calculated value was compared with the measured value. An good agreement was achieved between the calculated characteristics and the experimental performance. We found that the designed antenna in this paper can be used as the omnidirectional antenna with reflectors and the analysis method in this paper can be used for the analysis of this type antenna.

• Journal of the Korean Institute of Telematics and Electronics
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• v.7 no.3
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• pp.12-18
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• 1970

In this paper, the radiation characteristics of a Circular Loop Antenna is studied in a moving homogeneous, isotropic and linear media with a constant velocity much less than the speed of light. In Stuffing the radiation characteristics, Srst vector potential on the loop antenna is derived in the moving media by appling Maxwell-Minkowaski's theory. Next, using the derived relations, the electric and magnetic Seld is calculated for the spec-i Sed wave length ana velocity of the media. The Seld patterns in the moving media are compared with those of stationary media. We find that the intensity of the field is reduced in the direction of the media velocity and increased in the opposite direction only for the component parallel with the plane of the antenna. The deviation from the stationary media is proportional to the velocity of the media and the frequency of source current.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.353-356
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• 2005

There have been many researches on the antenna performance degradation with the presence of the human body around the antenna structure to accomodate personal communication service [1][2]. To better understand the human body effects on the antenna resonance, radiation pattern, and input impedance, simulation was carried out with changing of the distance between antenna and lossy material. Effects on the antenna performance by the surrounding materials are also important in the case of the RFID system. It is desirable that the tag antennas for RFID system must reveal isotropic radiation pattern as well as attain the good impedance matching. In this paper, we investigated the antenna resonance and input impedance characteristic when there exist a lossy material sphere near various types of antenna at 900 MHz. In short antenna resonance was mostly affected by lossy material in the case of a rectangular loop antenna, and impedance variation was smallest in the case of a halfwave dipole.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.12 s.115
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• pp.1240-1248
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• 2006

This paper presents an UHF band(911 MHz) RFID tag antenna which has near-isotropic radiation pattern and easy conjugate impedance matching characteristics to any commercial chips of usual practice through the application of an inductively-coupled feeding. The proposed antenna of compact size $40{\times}46mm\;(0.12{\times}0.14{\lambda})$ has, at normal incidence, the maximum RCS of $-18.5dBm^2$ and the 3 dB RCS bandwidth of 9 MHz(1 %) in case of short chip load. It has the maximum and minimum RCS' of $-16.9dBm^2\;and\;-21.4dBm^2$ depending on the incident angles. The difference of about 4.5 dB is relatively small compared with that (about 70 dB) of a pure dipole antenna. The designed antenna has been fabricated and its RCS' have been measured varying the angles of incidence. The measured RCS' have been found to have good agreement with the simulated ones.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.12 s.103
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• pp.1206-1212
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• 2005

In this paper, we propose a novel antenna structure which uses the electric and magnetic currents so as to eliminate nulls on their radiation pattern. The tag antenna was matched to the conjugate impedance of the commercial tag chip using the modified double T matching network. The radiation efficiency is about $90\%$, and the bandwidth($S_{11}< -10 dB$) is 848${\~}$926 MHz. Also it shows the gain deviation between the maximum and minimum gains about 4 dB at any direction of the tag antenna at the operating frequency. The readable range of the tag is 1.7${\~}$2.4 m for an arbitrary rotation angle of the tag with a commercial tag chip.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.1
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• pp.98-105
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• 2013

This paper presents a finite-difference time-domain(FDTD) simulation and a data processing technique for radar sensing of the internal structure of a wall using an ultra-wide band antenna. We first designed an ultra-wide band anti-podal vivaldi antenna with a frequency range of 0.3~7 GHz which is chosen to be relatively low after considering the characteristics of wave attenuation, wall penetration, and range resolution. In this study the two-dimensional FDTD technique was used to simulate a wall-penetration-radar experiment under practical conditions. The next, the measured radiation pattern of the practical antenna is considered as an equivalent source in the FDTD simulation, and the reflection data of a concrete wall and targets are obtained by using the simulation. Then, a data processing technique has been applied to the FDTD reflection data to get a radar image for remote sensing of the internal structure of the wall. We compared the two different source excitations in the FDTD simulation; (1) commonly-used isotropic point sources and (2) polynomial curve fitting sources of the measured radiation pattern. As a result, when we apply the measured antenna pattern into the FDTD simulation, we could obtain about 2.5 dB higher signal to noise level than using a plane wave incidence with isotropic sources.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.5
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• pp.523-532
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• 2008

In this paper, we proposed a U-shaped RFID tag antenna with isotropic radiation characteristic for the stable operation of RFID system. The proposed antenna is composed of a U-shaped half wavelength dipole and a rectangular-shaped feed. In order to have good impedance matching with a tag chip, the commercial tag chip is attached to the lower center of the feed. A gain deviation characteristic of the U-shaped tag antenna can be further improved by inserting a rectangular slit in the lower center of the U-shaped antenna body. On the condition of VSWR<2, the tag antennas of two structures satisfy the Korea UHF RFID bandwidth and showed the gain deviation of less than 1.63 dB and 0.74 dB for without slit and with slit, respectively. On the condition of VSWR<5.8, the U-shaped tag antenna showed the gain deviation of less than 3.8 dB and 1.2 dB for without slit and with slit, respectively.