Department of Physical Sciences

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https://repository.run.edu.ng/handle/123456789/74

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Browsing Department of Physical Sciences by Subject "Attenuation"

Now showing 1 - 3 of 3
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    Laser Communication and Atmospheric Impairments
    (Global Scientific Journals, 2021) Sanyaolu, Modupe
    Varieties of signal-loss components in transmitting a laser signal beam from one point to another over microwave link are usually encoun tered due to absorption and dispersion by airborne molecules and aerosols and distortion of the wave-front due to atmospheric turbulence resulting from the variation of the refraction index along the direction of the beam. This paper provided information on calculating attenua tions generated as a result of these aerosols and hydrometeors effect on laser beams. Effective linking equipment, open-loop power control and feedback loop power control are suggested as mitigation techniques that significantly reduce attenuations when laser signals are transmitted
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    Performance of Rain-Induced Attenuation Prediction Models for Terrestrial Link in Cameroon
    (IJEAST (http://www.ijeast.com), 2022) Sanyaolu, Modupe
    Weather, notably rain, has a negative impact on radio wave propagation between terrestrial and earth-space links at frequencies above 10 GHz. Therefore rain-induced attenuation is a significant propagation impact that must be considered when designing satellite communication systems. Analysis of rain attenuation for earth-space links in three locations in Cameroon at V, Ku and Ka bands is investigated using four rain attenuation models: The ITU-R P.618 model, Svjatogor model, Garcia Lopez model and Bryant model at 42.5° elevation angles. The major goal is to figure out which rain attenuation prediction models are best for satellite communication in this area. Five years (2013–2017) daily rainfall data obtained from the Tropical Rain Measuring Mission-Precipitation Radar (TRMM-PR) and Global Precipitation Measurement (GPM) mission's Core Observatory were used for this study. The results showed that the ITUR P.618, Garcia-Lopez, and Svjatogor models performed best in this region. Attenuation ranged from 15 dB to 16 at 42.5° elevation angle for time exceedance of 0.01% at Ku band in all the study locations. For the Ka-band, attenuation varied between 32 dB and 38 dB. Signal availability at Ku-band is possible based on predicted rain attenuation values for 0.01 %-time exceedance. At Ka and V-band, the predicted rain attenuation values for 0.01%-time exceedance have shown that availability of signal is impossible, which infers losses of the signal during such rainfall events across the selected locations in Cameroon.
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    Rain Fade Analysis at C, Ka and Ku Bands in Nigeria
    (iiste.org, 2019) Sanyaolu, Modupe
    Rain fade has continued to be a major concern to communication systems designers. The effect of these dynamic fluctuations of the received signal due to rain is very pronounced in the tropical region. This paper pertains to the analysis of rain fades at C, Ku and Ka bands at some selected stations covering the main geographical zones of Nigeria. The ITU-RP propagation model was used to calculate the fade depth at 6 GHz, 8 GHz, 12 GHz, 16 GHz, 20 GHz, 30 GHz and 40 GHz. The rain fade correlate with signal attenuation. Attenuation distributions for percentages of time for signal unavailability were also estimated. The results show that values of attenuation for vertically and circularly polarized signals are less than those of the horizontal polarization at all the frequencies. It is found that rain fade is less severe in the Northern part of the country and is most severe in the southern part of Nigeria, with Port Harcourt, Lagos and Nsukka experiencing the highest rain impairment