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Author: search.filters.author.Leelaruji, N.

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    Comparison between foF2 observations and IRI-2001 model predictions at Thailand equatorial latitude station
    (2008-10-06)
    Wichaipanich, N.
    ;
    Boonchuk, T.
    ;
    Leelaruji, N.
    ;
    Hemmakorn, N.
    ;
    Supnithi, P.
    In this paper, the comparison between the F2-layer critical frequency (foF2) observations and international Reference Ionospheric (IRI) model predictions is presented. The data used for this study are obtained from bottomside ionogram recorded by the FM/CW ionosonde at Chumphon campus of King Mongkut's Institute of Technology Ladkrabang (latitude 10.72°N and longitude 99.37°E), Thailand, located near the magnetic equator. The measurement data coverage from January to December of a low solar activity year (2006) is analyzed based on the diurnal, seasonal variation and then compared with IRI-2001 model predictions. Generally, the foF2 obtained from the IRI (URSI and CCIR) model closely follows observed foF2 values. Comparing the results of URSI and CCIR options for foF2, we find that for low solar activity, both the URSI and CCIR options of the IRI model give foF2 values close to the ones measured at Chumphon, but the CCIR results produce smaller range of deviation than the URSI results. All comparative studies give feedback for new improvements of CCIR and URSI IRI models. ©2008 IEEE.
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    Modeling and measurement of airplane flutter phenomena on TV broadcasting signal
    (2008-06-01)
    Wongkeeratikul, A.
    ;
    Supnithi, P.
    ;
    Noppanakeepong, S.
    ;
    Leelaruji, N.
    ;
    Hemmakorn, N.
    This paper presents a novel approach to model TV signal due to airplane flutter phenomena. The three components of the modeling are based on 1) Bistatic radar cross sections (RCS) of an ellipsoid, 2) 3-dimensional geometry consideration technique to calculate the distance difference between direct and reflected waves due to airplane, and 3) Ray theory, based on physical and geometrical consideration. Unlike previous works, the model takes into account of realistic parameters such flying height, distance from the airport, flying angle, altitude, aircraft body type and others. The simulation results are then compared with measurement results at 60.75 MHz and 208.75 MHz. The results have shown good agreement between simulation and measurement patterns. © 2008 IEEE.
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    The analysis of ionospheric scintillation on the global Positioning System (GPS) at Bangkok
    (2006-12-01)
    Theerapatpaiboon, P.
    ;
    Supnithi, P.
    ;
    Leelaruji, N.
    ;
    Hemmakorn, N.
    This paper presents analysis of ionospheric scintillation on GPS signal (1575.45 MHz) by using the GSV4000 GPS receiver installed at KMITL. The characteristic of ionospheric scintillation on GPS signal are analyzed by employing S<inf>4</inf> index to identify the amplitude scintillation and σ<inf>ø</inf>(60 sec) to identify the phase scintillation, From the results, we found that the ionospheric scintillation phenomena impact on the GPS signal leading to the error in the global positioning system, differ from the non-scintillation period more than 20 meters. © 2006 ICASE.
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    The effects of sumatra-andaman earthquake on total ionospheric electron content (TEC) and ionospheric scintillation of GPS signal in thailand
    (2005-12-01)
    Theerapatpaiboon, P.
    ;
    Leelaruji, N.
    ;
    Hemmakorn, N.
    ;
    Supnithi, P.
    This paper presents the effects of Sumatra-Andaman earthquake (26 December 2004) on the total ionospheric electron content (TEC) by using the TEC Meter (JAVAD) installed at KMITL. From the results, we found that the total ionospheric electron content enhancement at the time of this earthquake is higher than other days about 7 TEC units. Furthermore, the study includes the effect of this phenomenon on GPS signal (1575.45 MHz) by employing S<inf>4</inf> index and σ<inf>φ</inf> (60sec) to identify the severity of amplitude scintillation and phase scintillation, respectively. From the observation, we can conclude that TEC variation is the cause of ionospheric scintillation leading to the position error on GPS about 8 meters. © 2005 IEEE.
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    The observation and simulation of the airpiane flutter on low band television broadcasting signal
    (2003-01-01)
    Wonggeeratigun, A.
    ;
    Sangonchat, P.
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    Noppanakeepong, S.
    ;
    Leelaruji, N.
    ;
    Moriya, Y.
    The paper studies effect of quasi-periodic or airplane flutter pheiiomcnon on television broadcasting. Airplane flutter is a very important problem. It causes the receiving antenna to receive both direct signal by the Tx (Transmitter antenna) and reflected signa1 scattered by the airplane with phase delay. The sum of two signals results in fading, sometime coilapse and distortion of picture on TV screen. W e performed measurement and modeling this phenomenon on TV signal when the airplane flew across and the range Tx and Rx (Receiver antenna). The frequency 60.75MHz (Aural frequency of CH3) is used under tests. A single scatter multipath model is introduced. It is used to duplicate some of the measured data and show the dependence of power variation on the airplane fluttering. Tlie fluctuation of the airplane flutter phenomenon was calculated to be around 2-4dB.