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Rain attenuation in broadband satellite
(2007-12-01)
Nukfron, Ekavit
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Hemmakorn, Narong
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Sitichepak, Suviporn
This paper presented the effects of attenuation from rain rate together with rain drop size distribution analysis on the model of transmitter broadband satellite in Ka-band frequency. We illustrated a new model by simulating transmission broadband signal and studied the rain attenuation which has effects to high frequency. The results of the model were represented by the relation between error probability and S/N. Moreover, the numbers of re-transmission cycles for completing the amount of data were also presented. The attenuation would be illustrated in log normal distribution forms and in PDF terms. The simulation would be run by taking error probability (Pe) of noise at 0.4, 0.04, 0.004 and 0.004. ©2007 IEEE.
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Rainfall rate and rain attenuation in Ku-Band satellite signal in Thailand and Laos
(2006-12-01)
Lakanchanh, Donekeo
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Datsong, Attasit
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Leelaruji, Nipha
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Hemmakorn, Narong
This paper describes the experiment of rainfall rate and rain attenuation. One year measurement of rainfall rate and rain attenuation of satellite signal on Ku Band, downlink of Thaicom 3 at King Mongkut's Institute of Technology Ladkrabang (KMITL) in Bangkok using 0.5 meter antenna with horizontal polarized and measurement of rainfall rate at National University of Laos (NUOL) in Vientiane and at Paksong in the southern of Laos are investigated, The relation of rainfall rate and rain attenuation on three ground stations are presented. Correlation between rainfall rate and cumulative time are described in monthly and yearly include the comparison of yearly cumulative rainfall rate between measurement and ITU-R model are presented. © 2006 ICASE.
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Propagation effect by rain in Ku and Ka band satellite communication system
(2006-12-01)
Lakanchanh, Donekeo
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Udomareyasap, Pongputhai
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Leelaruji, Nipha
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Hemmakorn, Narong
This paper present the contribute of rainfall rate and rain attenuation in Ku band measurement and prediction rain attenuation in Ka band by using ITU-R model at King Mongkut's Institute of Technology Ladkrabang (KMITL), Bangkok, Thailand. One year measurement of rainfall rate and rain attenuation of Ku band satellite signal of 59 degree elevation angle is presented. The experimental results, we found that on the rainfall rate R<inf>0.01</inf> is 90 mm/hr, the measured Ku band rain attenuation A<inf>0.01</inf> is about 11 dB while predicted Ka band rain attenuation is 20 dB, The effect of rain attenuation characteristics of Ka band and Ku band satellite signals are compared. © 2006 IEEE.
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Detection of ruptures of Andaman fault segments in the 2004 great Sumatra earthquake with coseismic ionospheric disturbances
(2006-09-04)
Heki, Kosuke
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Otsuka, Yuichi
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Choosakul, Nithiwatthn
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Hemmakorn, Narong
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Komolmis, Tharadol
We Near-field coseismic perturbations of ionospheric total electron content (TEC), caused by direct acoustic waves from focal regions, can be observed with Global Positioning System (GPS). They appear 10-15 min after the earthquake with typical periods of ∼4-5 min and propagate as fast as ∼1 km/s toward directions allowed by ambient geomagnetic fields. Ionospheric disturbance, associated with the 2004 December 26 great Sumatra-Andaman earthquake, was recorded with nine continuous GPS receiving stations in Indonesia and Thailand. Here we explore the possibility to constrain the rupture process of the earthquake with the observed ionospheric disturbances. We assumed linearly distributed point sources along the zone of coseismic uplift extending ∼1300 km from Sumatra to the Andaman Islands that excited acoustic waves sequentially as the rupture propagate northward by 2.5 km/s. TEC variations for several satellite-receiver pairs were synthesized by simulating the propagation of acoustic waves from the ground to the ionosphere and by integrating the TEC perturbations at intersections of line of sights and the ray paths. The TEC perturbations from individual point sources were combined using realistic ratios, and the total disturbances were compared with the observed signals. Prescribed ratios based on geodeticatly inferred coseismic uplifts reproduced the observed signals fairly well. Similar calculation using a rupture propagation speed of 1.7 km/s degraded the fit. Suppression of acoustic waves from the segments north of the Nicobar Islands also resulted in a poor fit, which suggests that ruptures in the northern half of the fault were slow enough to be overlooked in short-period seismograms but fast enough to excite atmospheric acoustic waves. Coseismic ionospheric disturbance could serve as a new indicator of faulting sensitive to ruptures with timescale up to 4-5 min. Copyright 2006 by the American Geophysical Union.
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The rain attenuation in Ku-band satellite signal at Bangkok
(2005-12-01)
Datsong, Attasit
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Hemmakorn, Narong
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Leelaruji, Nipha
This paper presents the experiment and result of rain attenuation of satellite signal on Ku-band, downlink of Thaicom 3 at King Mongkut's Institute of Technology Ladkrabang (KMITL) in Bangkok (Longitude: 100.7 °E, Latitude: 13.7 °N). The relation of rainfall and the rain attenuation on ground station are presented. Correlation between 1-second, 1-minute and 30-minute integration time of the rainfall rate is also presented. We compare the data recorded at Bangkok with ITU-R model. This experiment has been held for 1 year from June 2004 to May 2005. © 2005 IEEE.
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Language-support system using character recognition
(2004-01-01)
Asai, Kikuo
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Sugimoto, Yuji Y.
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Hemmakorn, Narong
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Osawa, Noritaka
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Kondo, Kimio
We have developed a prototype system that supports language translation for distance lecturing and local learning. The system automatically detects a word displayed in a video image by matching the identified character markers; it then translates the word into the other language and displays the translated word using text, image, and/or sound. The ARToolkit is used as an image-processing tool to search the video image for character markers, which are composed of square .frames and registered characters. The use of image processing enables any language to be used as the source language; Japanese is used in the prototype. The use of video makes it easy to implement the system in existing telecommunication systems, because a user just prepares a PC for capturing video images. A Web browser is used as the presentation tool; it can handle any content format normally supported by a Web browser: images, sounds, 3D models, and characters. An automatic voice function automatically reads out words on user demand. The software consists of a character-recognition part (server) and a display part (client); the server controls the client through socket communications. This software architecture makes it possible for one lecturer to simultaneously teach students with various mother tongues, when the clients treat multi-language, because there is a different client for each student. Testing of this language-support system for distance lecturing between Thailand and Japan using a satellite communication system showed that it could be used for both fundamental language lecturing and language translation during international exchange.
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Satellite due to rain fading at Klong downlink availability of Thaicom 3 Yai ground station
(2000-12-01)
Chaisang, Aditep
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Hemmakorn, Narong
This article reports the study of rain rates and rain attenuation on satellite signal at Klong Yai district, Trad province. This area has heaviest rainning in the country more than 4000 mm/year. We measured downlink signal of Thaicom 3 satellite at 12.271 GHz horizontal polarization. The period of recorded data are from January to December 1998. We analyzed data in the form of percentage of time in one year both rain rate and rain attenuation. Those values always use for link margin calculation of R<inf>0.3</inf>, R<inf>0.1</inf>, R<inf>0.05</inf>, R<inf>0.03</inf>, R<inf>0.01</inf> are 42, 84, 120, 162, and 222 mm./hr. respectively. Rain attenuation of A<inf>0.3</inf>, A<inf>0.1</inf>, A<inf>0.05</inf> are 8.9, 15.5 and 20.1 dB respectively. The worst month are August and September. These values are higher than ITU-R rain zone P, Global rain zone H at 0.01% of time are 75 mm/hr and 10 mm/hr. As for attenuation, our measurement values are higher than ITU-R rec. 618-3 about 1 dB at 0.05% of time. After that we approximate the down link rain fall availability of the signal by calculate C/N from general link design equations.
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Rain rate estimation by simplified method using UHF wind profiler measurement at KMITL
(2000-01-01)
Somboonlarp, Chaiwat
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Leelaruji, Nipha
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Hemmakorn, Narong
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Manyanon, Apinan
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Ohno, Yuichi
In this paper, we propose a simplified method for rain rate estimation only using simple parameters instead of the fitting or retrieval calculation using data of UHF wind profiler measurement, which operated by King Mongkut's Institute of Technology Ladkrabang (KMITL) in Bangkok, Thailand. The simple parameters in this method use only the peak position of rain echo and Doppler velocity of clear air echo from Doppler spectral for estimated rain drop size distribution (DSD), which more important to calculate rain rate. Doppler spectra of UHF wind profiler at KMITL during the rainy season are used for testing the availability of this simplified rain estimation method. Rough agreement between rain rate estimation from the surface rain gauge and UHF wind profiler at KMITL can be seen at the range of low rain rate. At the range of high rain rate, the estimation by this method does not correspond to the surface rain gauge since the Doppler spectra seems saturated with too strong rain echo.
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Lower atmospheric wind observation by L-band Doppler radar in Thailand
(2000-01-01)
Leelaruji, Nipha
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Somboonlarp, Chaiwat
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Sangonchat, Parichart
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Hemmakorn, Narong
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Manyanon, Apinan
The study of low atmospheric boundary layer wind by wind profiler radar is the aim of this present. The L-band Doppler radar used as the meteorological equipment using operating frequency 1357.5 MHz. The transmitter radiates the pulse signal of peak power 1 kW through the upper air. The single parabolic antenna is steering into three directions, vertical, north and east respectively. This radar received the echo scattered back by the irregularity of atmospheric refractivity along the beam. The Doppler shift frequency deviates by the movement of turbulent are used to calculate the wind velocity and wind direction. The observation height starts from 150 meters to 4 km. The diurnal and seasonal wind had been observed for six years continuously. It shows the variation of wind in each year, which correspond to Asia monsoon, Northeastern monsoon and Southwestern monsoon. While the radio sonde, which operates by radio propagation technique is used for wind measurements too. The comparisons of both systems are present in correlation method.
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Satellite radio wave propagation experiments in Thailand
(1998-01-01)
Hemmakorn, Narong
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Kitsadawanich, Surasak
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Leelaruji, Nipha
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Igarashi, Kiyoshi
This paper presents 2 items of satellite radio wave propagation experiments. The first experiment is to determine the variation of total ionospheric electron content (TEC) in Thailand, by using the correlation of different time delay of two L-band signals from GPS satellite. This experiment was conducted as a part of the Post-PARTNERS project of MPT, Japan. The results show that the lowest of diumal variation of TEC is just before sunrise and peak during 13:00-15:00 LT. The standard deviation of TEC data in day-time is about 15% and about 25% in night-time, the peak value occur during 2:00-5:00 LT. with 40-70% SD. The irregularity of electron density in ionosphere in night-time is greater than that in the day-time and it may cause the scintillation occured in satellite receiving signal. The second experiment is to study the down link satellite signal characteristic from Thaicom 1 and Thaicom 2 satellite. Both down link frequencies are in Kuband with different polarization. Thaicom 1 transmits in horizontal polarization while Thaicom 2 transmits in vertical polarization. The data are analyzed in two cases, the first is to analyze the amplitude scintillation characteristics. We found that the scintillation occurrence has a certain relation with the atmospheric temperature at high elevation angle and frequently occurred about 9:00 to 17:00 LT. and the maximum occurrence numbers occur during 13:00 to 15:00 LT. And the second is to analyze the receiving signal attenuation with respect to rain rate. The attenuation of signal level for one year are continuously recorded on strip charts. The result of the attenuation of receiving signal are varied due to rain rate. If the rain rate about 120 mm/hr then the received signal decrease about 4 dB/km. A comparison between the measured values and predicted value by CCIR are shown. The attenuation signal decrease about 15.4 dB, at the yearly cumulative percentage of time 0.01%. The largest value of path attenuation by rainfall is about 22 dB at the yearly cumulative percentage of time less than 0.001%.

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