• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.272-275
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• 1997

Noninvasive multifrequency microwave radiometry using coaxial waveguide antenna has been investigated for a homogeneous and our layer human body model. We derived finite-difference time-domain(FDTD) algorithm and equation of MUR and generalized perfectly matched layer(GPML) absorbing boundary conditions(ABCs) in cylindrical coordination. The coupling between coaxial waveguide antenna and a biological object was analyzed by use of the FDTD method using MUR and GPML ABCs to obtain the absorbed power patterns in the media. The specific absorption rates(SAR) distribution which was corresponding to the temperature distribution was calculated in each region by use of the steady-state response in FDTD method. The SAR patterns of FDTD method using MUR ABCs was compared with those of FDTD method using GPML ABCs.

• Journal of Biomedical Engineering Research
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• v.18 no.3
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• pp.261-266
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• 1997

Nonevasive multifrequency microwave radiometry using coaxial waveguide antenna has been investigated for a homogeneous and four layer human body model. The coupling between coaxial waveguide antenna and a biological object was analyzed by use of the finite-difference time-domain(FDTD) method to obtain the absorbed power patterns in the media. The object studied in this paper was a homogeneous and four-layered lossy medium. The specific absorption rates(SAR) distribution which was corresponding to the temperature distribution was calculated in each region by use of the steady-state response in FDTD method. The SAR pattern of 1.2GHz was compared with that of 1.8GHz.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.9
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• pp.12-20
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• 2013

In this paper, a co-planar waveguide(CPW) fed zeroth-order resonant(ZOR) antenna with frequency reconfigurable radiating structures is fabricated and measured. The unit cell of proposed antenna consists of a series metal-insulator-metal(MIM) capacitor and two shunt line inductors which are shorted through the via. The proposed antenna is designed based on a composite right/left-handed(CRLH) transmission line with two unit cells and it has open ended structure in order to radiate electromagnetic energy mainly on the shunt arm. In order to reduce the antenna size and to exhibit a frequency reconfigurable ability using diode switches four straight strips bent by 90 degrees are used as shunt inductors. The total size of fabricated antenna is $0.22{\lambda}_0{\times}0.16{\lambda}_0$ at zeroth-order resonant(ZOR) frequency. The measured maximum gain and bandwidth (VSWR ${\leq}2$) are 3.1 dBi and 56MHz at ZOR frequency of 2.97 GHz, respectively. This type of antenna can be applied to a frequency reconfigurable antenna system with triple bands.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.11
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• pp.1020-1026
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• 2015

In this paper, the design of longitudinal shunt slot array monopulse antenna in the broad wall of waveguide for Ka band millimeter-wave seeker, Dip-Brazing method for fabrication and experiment results are presented. The proposed antenna consists of radiating slots by using Elliot's array synthesis procedure, probe-exciting feed structure for improving the return loss bandwidth and monopulse comparator. Element weigthings in the array have been calculated by continuous Taylor aperture distribution. Also, the simulation tool has been used to characterize the individual isolated slot, which has subsequently been used in Elliot's method to design the slot array efficiently. The designed antenna is fabricated using Dip-Brazing method. The gain of measured antenna is 28.4 dBi. Antenna beamwidth and side lobe levels are similar to the design result we expect.

• Journal of electromagnetic engineering and science
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• v.18 no.3
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• pp.154-159
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• 2018

In this paper, electromagnetic radiation from a slot array antenna enclosed by a Von Karman radome is analyzed by using the ray tracing method and Huygens's principle. We consider the rectangular slot array antenna and the Von Karman radome. The radiation patterns are calculated by using the surface currents of the radome to illustrate the electromagnetic behaviors of the radome-enclosed waveguide slot array antenna.

• ETRI Journal
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• v.27 no.6
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• pp.677-684
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• 2005

A phased array antenna was fabricated using four-element ferroelectric phase shifters with a coplanar waveguide (CPW) transmission line structure based on a $Ba_{0.6}Sr_{0.4}TiO_3(BST)/MgO$ structure. Epitaxial BST films were deposited on MgO (001) substrates by pulsed laser deposition. To attain the large differential phase shift and small losses for a ferroelectric CPW phase shifter, an impedance-matching-part adding technique between the effective transmission line and connecting cable was used. The return loss and insertion loss for this techniqueadapted BST CPW device were improved with respect to those for a normal BST CPW device. For an X-band phased array antenna system consisting of ferroelectric BST CPW phase shifters, power divider, dc block, patch antenna, and programmed dc power, the steering beam could be tilted by $15^{\circ}$ in either direction.

• ETRI Journal
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• v.32 no.3
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• pp.472-474
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• 2010

In this letter, a novel zeroth-order resonant (ZOR) antenna on vialess co-planar waveguide (CPW) is proposed. It is based on a composite right/left-handed CPW transmission line. To achieve a compact size, this antenna utilizes the ZOR condition, and its reactive parameters determine the resonant frequency. Each unit cell is composed of a metallic top patch and meander lines. Since it is realized on the CPW single layer, the proposed antenna has the benefits of being a compact size and easy to fabricate. The bandwidth of 6.8% and efficiency of 62% are experimentally achieved. Its bandwidth is enhanced compared with other ZOR antennas.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.11
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• pp.1294-1302
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• 2008

A design approach for a radiation element of dual polarization, which can be implemented in the waveguide structure, is proposed. For minimization of the radiating element, the ridged waveguide type is used and for dual polarization, the microstrip type of printed dipole structure is additionally installed inside the waveguide. In order to validate the design approach, $1{\times}4$ array antenna is fabricated and its performances such as return loss, co-polarization coupling between adjacent channels, and radiation patterns are investigated. Theory and experiment are observed to be in good agreement. The radiating structure is thought to be a useful one in an application to the phased array antenna system, in particular, requiring dual polarization characteristics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.8
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• pp.684-692
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• 2016

In this paper, a non-offset longitudinal shunt slot excited by an asymmetry compound iris on the broad wall of a rectangular waveguide is presented as an element for a waveguide slot-array antenna(WSAA). By properly adjusting the iris dimension, a resonance of the slot at a desired frequency can be achieved. The proposed resonant slot has some advantageous properties, such as a wide range of normalized resonant conductance, and minimum change of phase in the waveguide at the resonance. In addition, when the slots are arrayed for a waveguide slot antenna, the unwanted cross-polarization level can be reduced because each slot is placed in a straight line. A $8{\times}1$ WSAA with -20 dB side-lobe level(SLL) is designed, fabricated, and tested experimentally. The measured results are well agreed with the simulated ones and have an SLL of -18.13 dB and a cross-polarization level of -48.85 dB at 9.41 GHz, which was improved by about 15 dB of that of the conventional longitudinal slot array antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.823-830
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• 2010

This paper deals with a coaxial-to-waveguide transition generating circularly polarized wave to be connected with horn antennas. By combining vertical coaxial fed structure, back-short and the polarization twisting structure, the circular polarization is successfully generated in the waveguide. The designed and implemented transition shows that the present structure can significantly reduce the size of the antenna part at X-band.