• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.12
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• pp.924-934
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• 2018

This paper describes the development and measurement results of C-band planar active phase array antenna for detecting and tracking radar(weapon-locating radar). The antenna is designed with 14 sub-arrays(12 main channels and 2 sidelobe blanking channels and approximately 3,000 elements of transmit-receive channel) to generate transmit and digital receive patterns. Using a near-field measurements facility, G/N, transmit patterns, and received patterns are measured. Receive patterns are implemented with digital beamforming by signal processing. The measurement results demonstrate that antenna design specifications were fulfilled.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.3
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• pp.264-272
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• 1997

This paper presents the analysis of forced resonance characteristics of electrically small dipole antenna loaded with external element and its application to measuring unknown frequencies. The method of moments with Galerkin's procedure is used to determine the current distribution of the antenna. To derive the determinantal equation of resonance lengths at a given frequency, small antennas with the reactance loaded can be treated as a two-port network. Numerical results show that the forced resonance of the electrically small dipole antenna loaded with reactance can be easily obtained by controlling the reactance for the series resonance as well as for the parallel resonance. It is demonstrated that the forced resonance characteristics can also be applied to the measurement of unknown frequencies.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.6C
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• pp.398-402
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• 2011

High resolution windspeed profile measurements are needed in a weather radar to provide the reliable information of rapidly changing weather conditions. However, it is necessary to remove both stationary and moving clutter to obtain the accurate pulse pair estimates. To overcome these problems, a simple adaptive array antenna may be applied to clutter removal. Using the simulated weather and clutter data, the clutter cancellation capability is analyzed for a weather radar with an adaptive antenna. The pulse pair estimates obtained from the adaptive weather radar are compared with those of the raw data.

• Smart Structures and Systems
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• v.1 no.3
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• pp.267-282
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• 2005

This work describes ongoing development of an embedded sensor system for the early detection and prevention of deterioration of reinforcing steel tendons within reinforced concrete. These devices will evaluate the condition of the steel tendon using ultrasonic techniques and then wirelessly transmit this data to the outside world without human intervention. The ultrasonic transducers and the interpretation of the sensed signals that allow detection and prognosis of tendon condition are detailed. Electrical characterization of concrete mixtures used in bridge construction is conducted and a wideband microstrip antenna is designed and fabricated to operate between 2.4 and 2.5 GHz when embedded in such a medium. Simulations and measurements of the embedded antenna element are presented. Transceiver selection and implementation are discussed as well as future work in operational protocols, sensor networking, and power sources. By implementing commercially available off-the-shelf components whenever possible, these devices have the potential to save millions of dollars a year in evaluation, repair and replacement of reinforced concrete.

• ETRI Journal
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• v.40 no.1
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• pp.26-38
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• 2018

To overcome considerable path loss in millimeter-wave propagation, high-gain directional beamforming is considered to be a key enabling technology for outdoor 5G mobile networks. Associated with beamforming, this paper investigates propagation power loss characteristics in two aspects. The first is beamwidth effects. Owing to the multipath receiving nature of mobile environments, it is expected that a narrower beamwidth antenna will capture fewer multipath signals, while increasing directivity gain. If we normalize the directivity gain, this narrow-beamwidth reception incurs an additional power loss compared to omnidirectional-antenna power reception. With measurement data collected in an urban area at 28 GHz and 38 GHz, we illustrate the amount of these additional propagation losses as a function of the half-power beamwidth. Secondly, we investigate power losses due to steering beam misalignment, as well as the measurement data. The results show that a small angle misalignment can cause a large power loss. Considering that most standard documents provide omnidirectional antenna path loss characteristics, these results are expected to contribute to mmWave mobile system designs.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.1
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• pp.77-83
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• 1999

Due to the high cost of constructing anechoic chamber, the multi-usage of a chamber in various applications is very effective in terms of cost as well as space. In this paper, we describe an anechoic chamber currently used at SK Telecom in Korea. This is designed for the measurements of both far/near field antenna and EMC/EMI in the identical chamber. This anechoic chamber and measurement system support antenna test in the frequency range of 150 MHz to 40 GHz and meet the requirement of ANSI C63.4 and CISPR 16.1 for EMC/EMI.

• Proceedings of the Korea Contents Association Conference
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• 2004.05a
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• pp.317-322
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• 2004

The improvement of a near-field measurement for an antenna is investigated. We propose the formula of a circular cylindrical scanning based on the Cartesian coordinate. Proposed algorithm for the circular cylindrical scanning is compared with the exact solution for a Hertzian dipole antenna, thus confirming that our approach is useful for most practical measurements.

• Journal of the Korean Institute of Telematics and Electronics
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• v.3 no.4
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• pp.5-15
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• 1966

The real part of the impedance of dipole antenna is computed rigorously instead of solving a boundary value problem of a partial differential equation. In this paper the resistance of the dipole antennas, whose shape was determined from an ordinary differential equation of first order and the length 2h is in the limits of , were computed and measured. The frequency used was 1500MC and the image screen, 93$\times$93$\textrm{cm}^2$ rectangular aluminium plate, was used for the measurements. The measured resistance was consistent with the theoretical result.

• Journal of electromagnetic engineering and science
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• v.13 no.2
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• pp.86-92
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• 2013

The present paper defines diversity gain for stationary users. This deals in particular with gathering the received signal statistics over possible user positions and orientations in space rather than over time, and to define a meaningful diversity gain related to the cumulative improvement of the performances of the 1% users with the worst receiving conditions. The definition is used to evaluate diversity gain for some typical small antennas in an extreme environment with only line-of-sight (LOS). The LOS environment is regarded as user-distributed 3D-random LOS caused by the statistics of an ensemble of stationary users with arbitrary orientations in the horizontal plane (2D), and with arbitrary orientations of their wireless devices in the vertical plane. Thus, an overall 3D-random distribution of user orientation is assumed.

• Journal of electromagnetic engineering and science
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• v.13 no.2
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• pp.104-112
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• 2013

A novel miniaturized artificial magnetic conductor (AMC) is proposed for dual-band operation. An AMC unit cell that employs four slots in the metallic patch is used to achieve miniaturization as well as easy control of the second/first resonant frequency ratio, which can be varied from 1.5 to 3.26 by simply changing the slot shape for a given metallic patch size. A dual-band antenna composed of a wideband monopole suspended over the proposed AMC surface is designed and tested to validate this approach. The measurements result in a satisfactory and good matching condition for the dual-band antenna.