KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 10 of 10

Some of the metrics are blocked by your
consent settings
Mitigate the GPS position error by neural network technique
(2008-12-01)
Nontasud, Sarawut
;
Leelaruji, Nipha
This paper presents the error reduction of GPS receiver due to ionospheric irregularities by neural network technique. Normally, when GPS signal passed through the irregularities of ionosphere the scintillation will be appeared. It causes to latitude and longitude error from reference position or pseudo-range error more than 10 meters. GPS position error depends on the strength of scintillation index or S4 which due to total electron content in the ionosphere (TEC).We used the measurement data which include the S4 index to analyze and correct the position error by neural network technique. The result of this research we found the position error can reduce to less than 1 meter. The positions average close to correct position. © 2008 SICE.
Some of the metrics are blocked by your
consent settings
Rainfall rate and rain attenuation model in Bangkok, Thailand
(2008-12-01)
Chankeaw, Natthapong
;
Udomariyasap, Pongputhai
;
Lakanchanh, Donekeo
;
Noppanakeepong, Suthichai
;
Leelaruji, Nipha
This paper describes the measurement of rainfall rate at King Mongkut's Institute of Technology Ladkrabang (KMITL), Bangkok, Thailand, by using satellite signal from Thaicom5. Three years measurement of rainfall rate are presented. The experimental results indicate that the measured rainfall rate are 90mm/hr in 2005, 94 mm/hr in 2006 and 102 mm/hr in 2007. Moreover, we have developed new modify prediction model of rain attenuation by ITU-R rain attenuation model. The model provides for prediction of annual and for expected year to year variations. This model applied to collecte data compared with ITU-R model. From the results of prediction model at KMITL, we found that the highest rainfall rate 102 mm/hr in 2007 cause to signal attenuate 14.34 dB. © 2008 IEEE.
Some of the metrics are blocked by your
consent settings
Applied the artificial neural network for reduce the position erroron GPS receiver due to ionospheric irregularities
(2008-12-01)
Nontasud, Sarawut
;
Leelaruji, Nipha
When the GPS signal pass through the ionosphere irregularities effect to rapid fluctuation of signal or scintillation occurred. This effect to the GPS receiver position error. This paper presents the error reduction of GPS receiver due to ionosphere irregularities by artificial neural network. The GPS position error depends on the strength of scintillation which measured in scintillation index or S4 index which due to total electron content (TEC) in the ionosphere. We used the measurement data which include the S4 index to analyze and correct the position error by artificial neural network. The result of this research we found the position error can reduce to less than 1 meter. The positions average close to correct position.© 2008 lEEE.
Some of the metrics are blocked by your
consent settings
Rainfall rate and rain attenuation in Ku-Band satellite signal in Thailand and Laos
(2006-12-01)
Lakanchanh, Donekeo
;
Datsong, Attasit
;
Leelaruji, Nipha
;
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.
Some of the metrics are blocked by your
consent settings
Propagation effect by rain in Ku and Ka band satellite communication system
(2006-12-01)
Lakanchanh, Donekeo
;
Udomareyasap, Pongputhai
;
Leelaruji, Nipha
;
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.
Some of the metrics are blocked by your
consent settings
The rain attenuation in Ku-band satellite signal at Bangkok
(2005-12-01)
Datsong, Attasit
;
Hemmakorn, Narong
;
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.
Some of the metrics are blocked by your
consent settings
Observation of ionospheric height changes at chumphon near the magnetic equator
(2005-12-01)
Attaviriyasuwon, Rungchai
;
Boonchuk, Thikumporn
;
Leelaruji, Nipha
;
Hemmakom, Narong
This paper presents the ionospheric height variation for station near the magnetic equator at Chumphon campus, King Mongkut's Institute of Technology Ladkrabang which located at longitude 99.3 °E latitude 10.7 ° N. Ionogram was obtained every 15 minutes during equinox period. All data was used to determine apparent height (h'F) and critical frequency (fof2), respectively, by using data analysis of ionogram. This paper remains in predicting spread F onset base on the ionospheric height changes only. Although we have observations during a month, the height variation anomaly and we found that the spread F occurrences seem to be related to time of appearance. © 2005 IEEE.
Some of the metrics are blocked by your
consent settings
Rain rate estimation by simplified method using UHF wind profiler measurement at KMITL
(2000-01-01)
Somboonlarp, Chaiwat
;
Leelaruji, Nipha
;
Hemmakorn, Narong
;
Manyanon, Apinan
;
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.
Some of the metrics are blocked by your
consent settings
Lower atmospheric wind observation by L-band Doppler radar in Thailand
(2000-01-01)
Leelaruji, Nipha
;
Somboonlarp, Chaiwat
;
Sangonchat, Parichart
;
Hemmakorn, Narong
;
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.
Some of the metrics are blocked by your
consent settings
Satellite radio wave propagation experiments in Thailand
(1998-01-01)
Hemmakorn, Narong
;
Kitsadawanich, Surasak
;
Leelaruji, Nipha
;
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%.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results