• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.223-226
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• 2004

This paper analyzes the accuracy of free space path loss and matched filter gain approximated by using a passband rectangular pulse for ultra wideband (UWB) radio systems. The example causal signal, a modulated Gaussian pulse with the same center frequency and frequency bandwidth of the passband rectangular pulse, is used to consider the accuracy. The path loss and matched filter gain of the modulated Gaussian pulse are simulated for the reference results. The UWB free space path loss is shown and is compared with that obtained from simulation and Friis' transmission formula. The UWB matched filter gain is shown and compared with simulation results. From the results, we can see that the UWB path loss formula is more accurate than the Friis' transmission formula. The results from the UWB free space path loss and matched filter gain formulas agree with the simulation. Then, these free space path loss and matched filter gain formulas approximated by using a passband rectangular pulse are appropriate for UWB system.

• The Journal of the Acoustical Society of Korea
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• v.22 no.7
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• pp.579-584
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• 2003

All of propagation path loss prediction models, which have been presented up to date, are oかy for ground living space. In reality, sea surface free space is different from ground living space in physical hierarchical structure. If the propagation path prediction model for ground living space is applied to the sea surface free space, propagation path loss will be smaller than actual value, while the maximum service straight line will become shorter. Thus this paper proposed and simulated the propagation path loss prediction model for predicting propagation path loss more accurately in sea surface free space, with its focus on CDMA mobile communication frequency band. Then the simulation results were compared to actual survey to verify its practicality.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.5
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• pp.87-92
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• 2011

In this paper, we got the 800 ~ 900 MHz path loss model for Russia PNG area using the free space model and the Okumura-Hata Model. In order to add new regional properties to the existing path loss model, the mean square error technique is used to obtain the correction factor. The correction factors for the free space and the Hata model are 28, 13 dB respectively. By applying this correction factors, the new Russain PNG path loss model is proposed.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.3
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• pp.194-198
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• 2011

In this paper, we obtained the path loss characteristics in the 850 MHz for Russia area by using the free space path loss model and Okumura-Hata path loss model. In order to extract the additional path loss model parameter from the new Russian regional properties, the mean square error technique is used to obtain the correction factor. According to the obtained correction factor, the differences for the free space and Hata path loss model are 17, 6 dB in the 5 ~ 10 Km, 28, 14 dB in the 10 ~ 15 Km, and 35, 18 dB in the 15 ~ 20 Km. By applying the correction factors, the appropriate partial path loss models for the measured Russain area are proposed.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.116-121
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• 2020

With the recent development of the 4th Industrial Revolution, efforts have been made to carry out communication in a smart factory, farm, etc. at low cost and reliably. Methods for utilizing empty frequencies using TVWS(TV White Space) have been studied which can be used locally within 30 km. However, there have not been many studies on Path-Loss model considering Korean environment. In this paper, the Path-Loss model is divided into LOS (Line Of Sight) and NLOS (None LOS). In case of LOS model, we checked the difference between Free space model, Friis model, 2-ray model and Hata model with measured data. In the case of NLOS model, we checked the difference between Lee Model, ITU-R526-3 Model with measured data. In order to overcome the difference in Korean environment, we derived a model that can be applied in LOS and NLOS and prove its usefulness through performance evaluation through simulation.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.12
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• pp.16-22
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• 1994

In this paper, transmitter and receiver modules for free space optical interconnection are implemented and characterized. In the transmitter module, bias circuitry which inject current into the direct modulated laser diode is fabricated and in the receiver module, p-i-n diode is integrated with an MMIC amplifying stage. Laser diode has a direct-modulated bandwidth of 2 GHz at 1.4 Ith bias while p-i-n diode and amplifying stage has a bandwidth of 1.3 GHz and 1.5 GHz, repectively. Optical interconnection has a bandwidth of 1.3 GHz and linearly transmit modulated voltage signal up to 1.5 Vp-p. Measured loss of optical interconnection is 5dB which is composed of optoelectronic conversion loss of 15 dB, electrical impedance mismatch loss of 6.7 dB in transmitter module and gain of 18 dB in receiver module. Seperation between transmitter and receiver can be extended up to 50 cm by using a lens.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.4
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• pp.369-376
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• 2002

The dielectric properties of cereal grains such as short-grain rough rice, brown rice and barley with various moisture contents were determined by measuring the attenuation and phase shift of the microwave signal trough the grain samples at 9.5GHz. The microwave free-space transmission measurement system consisted of sample holder, horn antenna and network analyzer. Dielectric constant and loss factor of grain samples increased with moisture content and bulk density and agreed well with previous research results. Moisture density, which is defined as the product of moisture content and bulk density, was proposed as a bulk density and variety compensation factor. The technique for measurement of dielectric properties based on free-space transmission may be useful for other particulate materials.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.8
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• pp.437-444
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• 2014

In this paper, we propose a path loss model with the multiple antennas and doppler shift for high speed railroad communication. Path loss model is very important in order to design consider diverse characteristic in high-speed train communication. Currently wireless communication systems use the multiple antennas in order to improve the channel capacity or diversity gain. However, until recently, many researches on path loss model only consider geographical environment between the transmitter and the receiver. There is no study about path loss model considering diversity effect and doppler shift. In order to make average residuals considering doppler shift we use tuned free space path loss model which is utilized for measurement results at high speed railroad. The environment of high speed rail is mostly at viaduct and flatland over than 50 percent. And in order to make average residuals considering multiple antenna we use theoretical estimation of diversity gain with MRC scheme. proposed model predict loss of received signal by estimating average residuals between diversity effect and doppler shift.

• Journal of Advanced Navigation Technology
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• v.28 no.3
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• pp.278-287
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• 2024

In this paper, telemetry link budget model for small launch vehicle is proposed, and telemetry link budget simulator is implemented. The proposed link budget model consist of geometry model and propagation loss model. The geometry model is calculation of look angle between ground station and small launch vehicle. The propagation loss model consist of free space loss, polarization loss, and de-pointing loss which are appropriate to the small launch vehicle flight environment. The proposed propagation loss model can be calculate propagation loss without complex calculation of propagation environments. The link budget simulator is implemented in MATLAB. The simulator calculate look angle, free space loss, polarization loss parameter, de-pointing loss and received signal level in ground station by using position of ground station, routing of small launch vehicle, 3-D radiation patterns of antennas.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.1 no.2
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• pp.131-136
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• 1997

In this paper, the input impedance of coaxial fed rectangular microstrip patch antenna located inside rectangular waveguide is calculated by using the cavity model and the mode excited in the waveguide by the patch antenna. The return loss and efficiency of the patch antennas as a function of feed position in. free space and in waveguide are calculated and compared. The maximum efficiency of the antennas in waveguide and in free space are obtained at different feed position.