• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.7
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• pp.39-47
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• 1992

This paper showed that theoretical site attenuation curves were obtained simply by the method of moments analysis for current integral equations on antennas. Since the expansion coefficients of driving and receiving points were calculated from the method of moments procedure, site attenuations were evaluated simply using these basic antenna parameters. Theoretical site attenuations were calculated with half-wave resonant dipoles connected directly to a 50 ohm receiving system and connected to a 72/50 ohm matching network, respectively. Results were compared with other theoretical studies reported so far. Also included were experimental results for site attenuations to prove the validity of theoretical analysis.

• International Journal of Computer Science & Network Security
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• v.22 no.3
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• pp.382-388
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• 2022

Satellite communication for high altitude platform stations (HAPS) and low earth orbit (LEO) systems suffer from dust and sand (DU&SA) storms in the desert regions such as Saudi Arabia. These attenuations have a distorting effect on signal fidelity at high frequency of operations. This results signal to noise ratio (SNR) to dramatically decreasing and leads to wireless transmission error. The main focus in this paper is to propose common relations between HAPS and LEO for the atmospheric impairments affecting the satellite communication networks operating above Ku-band crossing the propagation path. A double phase three dimensional relationship for HAPS and LEO systems is then presented. The comparison model present the analysis of atmospheric attenuation with specific focus on sand and dust based on particular size, visibility, adding gaseous effects for different frequency, and propagation angle to provide system operations with a predicted vision of satellite parameters' values. Skillful decision and control system (SD&CS) is proposed to control applied parameters that lead to improve satellite network performance and to get the ultimate receiving wireless signal under bad weather condition.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.6
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• pp.483-495
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• 2008

The paper presents a numerical study to evaluate the phase velocities and attenuations of the average longitudinal and shear ultrasonic waves resulting from multiple scattering in fiber-reinforced composites. A computational procedure developed in this work is first used to produce a random, yet largely even distribution of fibers. Both the viscoelastic epoxy matrix and lossless randomly distributed graphite fibers are modeled using the mass-spring-dashpot lattice model, with no damping for the latter. By numerically simulating ultrasonic through-transmission tests using this direct model of composites, phase velocities and attenuations of the longitudinal and shear waves through the composite are found as functions of frequency or fiber concentration. The numerical results are observed to generally agree with the corresponding results in the literature. Discrepancies found in some detail aspects, particularly in the attenuation results, are also addressed.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.1 no.1
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• pp.14-19
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• 1990

A site attenuation measurement system has been developed and evaluated. The system uses selfresonant dipole antennas and baluns. Using the system we measured the site attenuations of the KSRI open area test site. The measured results agree with calculated data within $\pm$3dB , so the site can be used for EMI/EMC measurements and antenna calibrations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.319-324
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• 2000

Sound insulation effect of periodically arranged circular rods is studied by numerical method (BEM) and model experiment in anechoic room. Five different cylinder groups of diameter from 48 mm to 27 mm are arranged, where each group consists of 5 rows of identical rods and area ratio is kept almost the same as 60%. Comparisons of results by BEM and experiment show the band gap frequency ranges are qualitatively in agreement, while experiments gives higher attenuations. Frequency shifted attenuations (BEM results) by first group (${\phi}$48), third group (${\phi}$34) and fifth group (${\phi}$27) show that attenuation curves are in reasonable agreements for both plane wave and point source.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1729-1734
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• 2000

Complex dispersion relations in a cylindrical, foam-lined duct were successfully identified by using an iterative Prony series method. Techniques for using the iterative procedure successfully are described in detail, particularly with regard to model order selection and the identification of parameter starting values. It is shown that modal wave speeds and spatial attenuations per wavelength can be derived from the complex dispersion relations obtained using the iterative procedure. In addition, a finite element simulation is shown to well represent corresponding experimental measurement in terms of modal wave speeds and spatial attenuations.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.9
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• pp.1336-1343
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• 1990

In this paper the theoretical analysis of the site attenuation was made on the concept of mutual impedance of antennas and the cause of characteristic hump in the site attenuation curve below 80 MHz is explained. The deviation between the FCC site attenuatios and the experimental results of an ideal open area test site at low frequencies(below 80MHz) was found to be the mutual coupling effects of the antennas under the FCC's measurement conditions. It seems desirable that the site attenuations curve of FCC document be revicused to the theoretical curves presented in this paper is long as the FCC's measurement conditions are to the applied.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1993.11a
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• pp.54-55
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• 1993

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.795-802
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• 2011

In this paper, the detailed design procedure of the Y-junction stripline isolator self-contained the filter circuit in the center conductor in order to maximize attenuations below value of 30 dB at 3rd order harmonics is presented. The HFSS is used to simulate 1.8GHz band isolator and the results are compared with the measurement data. These results confirms that the designed stripline isolator is effective in achieving high attenuation above -30 dB at 3rd order harmonics. And it is obtained that the harmonic band of isolator using the ferrite of 0.16T is moved far from operating frequency more 1.2 GHz than one using the ferrite of 0.12T.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.7
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• pp.1433-1438
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• 2011

Relative attenuations of Tx and Rx in K-PCS and US-PCS duplexers were about -60dB and -65dB, -51dB and -53dB, respectively. In the case of Rx and Tx in K-PCS and US-PCS bandpass filters, relative attenuations were about -40dB and -14dB, -5dB and -10dB, respectively. From the aboved results, the relative affect between Tx and Rx in K-PCS bands was smaller than that of US-PCS bands. Also, the various capacitances of passband were important role to determine the characterics of bandpass filter.