• Journal of electromagnetic engineering and science
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• v.14 no.3
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• pp.278-283
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• 2014

This paper presents a theoretical approach for a modified turnstile antenna suitable for satellite communication in order to investigate the current distributions of radiators and radiation characteristics with equivalent model analysis. The proposed equivalent model is composed of an ideally horizontal dipole antenna and vertically loaded top-hat radiating elements. The required isoflux pattern with wide beamwidth has been achieved by attaching top-hat elements to the main radiators. In addition to illustrating radiation patterns, electrical performances like current distributions have been analyzed by mathematically manipulating the equations derived from the equivalent horizontal and vertical dipole model.

• Journal of IKEEE
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• v.25 no.2
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• pp.408-411
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• 2021

This paper presents a new reflectarray antenna capable with 1-bit switchable capability for W-band beamforming network. The proposed antenna has been optimized using two unit-cells with sizes of 1.0 mm and 1.3 mm to form a total number of 193 radiating elements on a square aperture surface of length 30 mm. These radiating elements are spaced 0.5 wavelengths apart and fed by a 15 dBi pyramidal horn antenna as the feed antenna placed 53 mm away from the aperture center. The proposed reflectarray achieves a realized peak gain of 22.52 dBi, a half-power beamwidth of 5.1° in both E- and H-planes at the test frequency of 80 GHz and operates over a wide bandwidth from 74 GHz to 90 GHz.

• The Journal of the Acoustical Society of Korea
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• v.15 no.1
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• pp.71-80
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• 1996

Characteristics of sleeve-gun arrays installed on the R/V Onnuri were analyzed and compared with survey data. In the case of cluster array, the beam width in the frequency range up to 814Hz is constant as $179.5^{\circ}$, and rapidly narrows in the frequency range of 814-1631Hz. However, in the case of long and wide arrays, as the frequency increases, the beamwidth decreases. The optimal frequency is 69Hz. the main lobe of vertical inclination has its maximum amplitude at phase angle $0^{\circ}$. The optimal frequency of cluster array which produces little side lobe is less than 1631Hz, and those of long and wide arrays are less than 108Hz. As a result, the cluster array produces a good source for high-resolution seismic survey, while the long and wide arrays are suitable for the survey of deep structures. The final high-resolution seismic section with cluster array was compared with that of long and wide arrays.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.842-849
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• 2010

This paper deals with a TT&C circularly polarized turnstile antenna for LEO satellites. The turnstile antenna consists of radiator for radiating power to free-space and power divider for generating circularly polarized wave. we presents a radiator to tolerate in space environments and a power divider to provide flat phase difference at wide bandwidth. The bandwidth of the proposed antenna covers the frequency bands of up- and down-link. The antenna shows wide beamwidth and enhanced axial ratio for unfavorable space environments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.2
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• pp.258-261
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• 2012

Helicopter-borne FMCW radar altimeter obtains the altitude information using the beat frequency between the transmitted and reflected signal from the nadir direction. However, the altitude error may exist when the strong echoes are received from the large RCS at the off-nadir direction because of the wide beamwidth of the altimeter antenna. In this paper, in order to investigate the effect of the altitude error due to the large RCS around the off-nadir direction, the reflected signals were measured by using the corner reflectors displaced on the several reference ground positions, and the acquired signals were analyzed and compared in the spectral domain. The analysis results can be used for the improvement of the altitude accuracy in the radar altimeter.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.317-322
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• 2005

Synthetic Aperture Radars(SAR) are used mainly for high-resolution imaging of the terrain. This paper describes the 16$\times$16 array antenna designed for an X-band, automobile-based SAR(AutoSAR) system. This antenna has the structure of several layers such as radome, radiators, slots, feed network, and honeycomb cores. Each layer is adhesively bonded to meet different combination of structural and electrical design requirements. Using the Strip-Slot-Foam-Inverted-Patch(SSFIP) structure and dogbone slots, a wide bandwidth and a structural hardness were achieved. Measurement results were compared with simulation results. It was observed that the SAR antenna had a bandwidth of 1.7 GHz, side-lobe levels of less than -20 dB, half-power beamwidth of 5$^{\circ}$, and gains of 25.0 dBi. The observed results show that the designed array antenna is suitable for the broadband AutoSAR system.

• Journal of electromagnetic engineering and science
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• v.10 no.3
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• pp.132-137
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• 2010

We present results of room-temperature characterization of lithographically manufactured antenna-coupled NbN micro-bolometers. The bolometers are assembled together with a hyper-hemispherical Si lens to couple the incident radiation to the bolometer from the back-side of the substrate. The bolometers are designed to operate at 300~1,000 GHz and they are characterized at 321~782 GHz. Radiation patterns are measured at 321 GHz, 400 GHz, 654 GHz, and at 782 GHz. The frequency dependency of the beamwidth is studied with several azimuthal beam profile measurements at 321~500 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.10
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• pp.761-768
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• 2017

In this paper, to implement the electromagnetic wave environment and solve electromagnetic compatibility(EMC) problem, miniaturization of ultra-wide band log periodic dipole antenna for measurement was investigated. In addition, in oder to improve the signal-to-noise ratio in high frequency band, balun was connected to the antenna to stabilize the operation of the differential mode antenna and the single mode coaxial cable. To minimize the total size and to increase bandwidth of the antenna, a fat dipole structure was used for the resonance frequency band below 4 GHz and a general dipole shape was used for that above 4 GHz. The bandwidth of the proposed antenna was represented from 0.6 GHz to 8.0 GHz with a ratio bandwidth of 12.3 : 1. Measured peak gain varies from 5.7 dBi to 9.1 dBi, and a half power beamwidth was presented from $29.4^{\circ}$ to $100.2^{\circ}$ in operating range.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.1
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• pp.42-52
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• 2012

In this paper, a waveguide antenna is designed and fabricated for side and rear radar sensor of vehicles in UWB (Ultra Wide Band) high band (center frequency : 9.5 GHz, -10 dB bandwidth : 600 MHz (6.4 %)). For the radar antenna, a probe fed rectangular waveguide antenna having simple structure and wide bandwidth is used. An important performance factor in this antenna is the isolation between transmitting (TX) and receiving (RX) waveguide antennas because this radar system uses TX and RX antennas separately. Thus the isolation between two antennas was simulated for E-plane and H-plane array. As a result, it was verified that the isolation of the H-plane array of the antennas is better than E-plane array, due to the TE10 mode. Therefore, H-plane arrayed waveguide antennas were mounted on a T-shaped radar module and performance of antennas was investigated. The -10 dB bandwidth of the TX and RX antenna mounted on T-shaped radar module was measured as 1000 MHz (10.52 %) and 1090 MHz (11.47 %) respectively and the isolation is less than -50 dB in the operation band. The peak gain is 7.65 dBi for the TX antenna and 7.26 dBi for the RX antenna and the beamwidth of H-plane of TX and RX antenna was measured as $64^{\circ}$ and $65^{\circ}$ respectively. Consequently, we verified that the proposed waveguide antenna is appropriate for a vehicle radar applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.2 s.105
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• pp.184-192
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• 2006

Synthetic Aperture Radars(SAR) are used mainly for high-resolution imaging of the terrain. This paper describes the $16{\times}16$ array antenna designed for an X-band, automobile-based SAR(AutoSAR) system. This antenna has the structure of several layers such as radome, radiators, slots, feed network, and honeycomb cores. Each layer is adhesively bonded to meet different combination of structural and electrical design requirements. Using the Strip-Slot-Foam-Inverted-Patch(SSFIP) structure and honeycomb cores, a wide bandwidth and a structural hardness were achieved. Measurement results were compared with simulation results. It was observed that this antenna had a bandwidth of 1.7 GHz, side-lobe levels of less than -20 dB, half-power beamwidth of $5^{\circ}$ and $5^{\circ}$, and gains of 25.0 dBi. The observed results show that the designed array antenna will be applicable to the wideband SAR system.