• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.3
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• pp.316-323
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• 2013

This paper deals with the near-field to far-field calculation for far-field characteristics of antenna and electromagnetic compatibility(EMC) testing. Since the conventional EMC testing process is inefficient such as measurements of the wide band signals and mega structures, Stratton-Chu formula is used to predict the far-field emission by simple and direct process. The usefulness of Stratton-Chu formula is verified by comparing to the analytic solution of the uniform distribution aperture in free-space. In order to inspect the far-fields and to get the near-field values, full-wave simulation solver is utilized. Through the full-wave simulation about the patch antenna, calculated far-field results from Stratton-Chu formula are proven. The predicted magnitudes of the far-field are in error by less than 6 %.

• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.466-472
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• 2003

In this paper, we proposed an optical true time-delay (TTD) feeder system for phased array antennas (PAAs). The system possesses high-speed beam scan capability since, in this scheme, different lengths of fiber delay-lines are selected by optical 2${\times}$2 MEMS switches at high speed. An optical TTD capable of beam scanning in one of eight different directions has been built for 10 GHz linear PAA systems. Experimental results on time delay measurements show that the maximum time delay error is less than 0.2 ps corresponding to a scan angle error of less than 0.84o. We have also designed a 10 GHz linear PAA composed of eight micro-strip patch antenna elements driven by the proposed TTD, and the radiation patterns of this PAA have been analyzed by simulation.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.2
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• pp.11-19
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• 1999

The design procedure as well as some test results of a low-cost commercial radome for mobile DBS(Direct Broadcasting Satellite) receiving antenna system are presented in this paper. At first the complex permittivity of dielectric material should be measured in order to select a material for radome design. The complex permittivities of low-cost plastics supplied by domestic vendors are measured and presented. And then the transmission losses of the sheets are calculated. The calculated results are verified by the measurements of wave transmission test of that sheets. Two kinds of radomes, ABS single-layer and A-Sandwich((PET-Foam-ABS), are fabricated and measured practically. The transmission losses of single-layer and A-sandwich radome are 1.5dB and 0.6dB respectively at the maximum wave incident angle of 57 degree. Also the calculated crosspolarization caused by A-sandwich radome is under 20dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.640-646
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• 2008

Design procedure of corrugated horn antenna for the mm-wave frequency range is presented, and hybrid condition in horn is calculated. In this paper, corrugate profiles of horn which satisfy both transition to balanced hybrid condition and fabrication possibility under the mm-wave short wavelength are obtained. Electromagnetic fields inside horn and corrugation are derived by the cylindrical mode theory. Propagation characteristics in the horn are calculated by the mode impedance matching method with boundary conditions, and radiation fields are obtained by the Kirchhoff-Hyugen principle to the horn aperture fields. A mm-wave corrugated horn antenna which operates on $85{\sim}115GHz$ is fabricated by electric forming method. Measurements show that VSWR is under 1.3:1 over whole band and the half power beamwidth on radiation pattern 9.2, 9.16 and 9.02 degree on 85, 100 and 110 GHz are agree well with theoretical calculation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.2
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• pp.121-126
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• 2004

This paper presents an SAR-data calibration technique using a well-calibrated scatterometer. At first a fully-polarimetric antenna pattern(magnitude and phase) of the antenna main-beam using a conducting sphere was measured. Then, this data were used to calibrate polarimetrically an auto-mounted network analyzer-based scatterometer system. This scatterometer system can be used to measure the accurate Mueller matrices of earth surfaces such as grass fields, rice fields and bare soil surfaces; i.e., the phase-difference parameters can be obtained as well as the radar scattering coefficients. If a polarimetrically calibrated scatterometer is operated at the same time with the SAR system, the scatterometer data can be used to correct the SAR data, especially the phase-difference parameters. It was found that the correction effect is remarkable for the degree of correlation ${\alpha}$, which is one of the phase-difference parameter, while the correction effect is negligible for the magnitude parameters(backscattering coefficients).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1892-1897
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• 2012

Modern electronic circuits are of importance for the function of communication, traffic systems and security systems. An intentional threat to these systems could be of big casualties and economic disasters. This study has examined susceptibility of electronic circuits inside the cavity by HPEM(High Power Electromagnetics). The UWB measurements were done at an anechoic chamber using a RADAN voltage source, which can generate a transient impulse of about 200 kV. The HPEM wave penetrated inside the metal case appeared to the long damped ringwave of pulse length compared with the incident wave. In addition, the resonant frequency generated inside the metal case occurred primarily in the range of 1~3 GHz. The frequency band of 1~3 GHz was influenced on the electronic circuit, which was confirmed by an external antenna and an internal absorber. The electronic circuit was influenced by HPEM infiltrated into the cavity at the 86 kV/m out of the metal cases. Also in case of an absorber the susceptibility of an electronic circuit was smallest among other cases(aperture, antenna). It is considered that absorber has a function absorbing electromagnetic wave infiltrated into the cavity and simultaneously limiting resonance by varying a boundary condition inside the cavity. Based on the results, electronic equipment systems could be applied to protection that has suited system requirements.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.23 no.2
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• pp.101-108
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• 2005

Inertial Navigation System has been used extensively to determine the position, velocity and attitude of the body. An INS is very expensive, however, heavy, power intensive, requires long setting times and the accuracy of the system is degraded as time passed due to the accumulated error. Global Positioning System(GPS) receivers can compensate for the Inertial Navigation System with the ability to provide both absolute position and attitude. This study describes a method to improve both the accuracy of a body positioning and the precision of an attitude determination using GPS antenna array. Existing attitude determination methods using low-cost GPS receivers focused on the relative vectors between the master and the slave antennas. Then the positioning of the master antenna is determined in meter-level because the single point positioning with pseudorange measurements is used. To obtain a better positioning accuracy of the body in this research, a wireless internet is used as an alternative data link for the real-time differential corrections and dual-frequency GPS receivers which is expected to be inexpensive was used. The numerical results show that this system has the centimeter level accuracy in positioning and the degree level accuracy in attitude.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.3
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• pp.336-344
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• 2011

The purpose of this study is to analyze the radiation-pattern characteristics above 1 GHz for the electromagnetic wave radiated from multi-slot such as ventilations, etc. on the enclosure of an EUT and so to make recommendations for suitable test methods. An experimental EUT was formed by putting a comb-generator at the center of a rectangular enclosure with 4 slots, and its radiation pattern was analyzed in the frequency range of 1~6 GHz. As analysis results, multi-lobe appears above 2 GHz and the number of multi-lobes is growing as the frequency increases. And real radiated-emission measurements were performed for the experimental EUT by scanning a receiving antenna in the height of 1~4 m and tilting toward maximum radiation, as well as setting the height of a receiving antenna to the central position of the EUT which is prescribed at the present standards. The measured results are +12.8 dB in the scanning and +16.4 in the scanning and tilting compared with the present standard test method. Therefore, the latter must be revised in order to consider the radiation pattern above 1 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.11
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• pp.1108-1115
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• 2004

A new type of a Rotman lens is presented in this paper fur millimeter-wave applications, such as collision avoidance radar. A dielectric slab Rotman lens is proposed to reduce the conductor loss and to create an appropriate farm for favorable implementation at millimeter-wave frequency. The proposed lens consists of a dielectric slab and slot lines whereas the conventional lenses are constructed with parallel conducting plates. The dielectric slab Rotman lens excited in TE$\_$0/ mode shows a high degree of confinement for the fields, low dispersion, and has an appropriate feed structure. A prototype lens has been designed and fabricated with 9 beam ports and 9 array ports together with 9 tapered slot antennas. This lens has been tested in the range from 10 GHz to 15 GHz and the measured beam widths are about 15$^{\circ}$ at 13 GHz. The measurements also show low mutual coupling between beam ports and an efficiency of about 34.6 %. The overall performance is comparable to that of conventional Rotman lenses even though the prototype was tested at lower than desired frequencies in the microwave frequency range due to our limited resources for fabrications and measurements. It is expected that at millimeter-wave frequency the dielectric slab Rotman lens will have lower conductor loss and lower mutual coupling than conventional Rotman lenses.an lenses.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.1
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• pp.47-54
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• 2014

Precise Point Positioning (PPP) algorithms using GPS code pseudo-range measurements were developed and their accuracy was validated for the purpose of implementing them on a portable device. The group delay, relativistic effect, and satellite-antenna phase center offset models were applied as fundamental corrections for PPP. GPS satellite orbit and clock offsets were taken from the International GNSS Service official products which were interpolated using the best available algorithms. Tropospheric and ionospheric delays were obtained by applying mapping functions to the outputs from scientific GPS data processing software and Global Ionosphere Maps, respectively. When the developed algorithms were tested for four days of data, the horizontal and vertical positioning accuracies were 0.8-1.6 and 1.6-2.2 meters, respectively. This level of performance is comparable to that of Differential GPS, and further improvements and fine-tuning of this suite of PPP algorithms and its implementation at a portable device should be utilized in a variety of surveying and Location-Based Service applications.