Abstract
Modeling of attenuation of Very High Frequency radio signal in residential environment can be very tedious as the channels are rarely characterized by vegetation of the same variety. This work focus on path loss measurement and attenuation modeling of the coherent scattered field intensity of VHF as it propagates through Mango and Jathropha trees. The two separate trees were illuminated uniformly with 2.15dBi dipole antenna connected to 60W transmitter while 1.7dBi short dipole connected to GSP-730 Spectrum Analyzer was used for reception. Path loss due to each canopy were estimated relative to the scattering angles. Dry-matter fraction of the leave were determined using sensitive weigh balance and corresponding effective dielectric properties of the leaves and branches peculiar to each tree were estimated using semi-empirical formula. Specific attenuation models were developed separately for the two trees relative to dielectric properties of each tree leaves and branches. The results show that path loss due to single Mango tree canopy ranges from 100dB to 140dB and that of Jathropha ranges from 95dB to 135dB. The results also show that total specific attenuation of the two trees depends on frequency, wavelength and dielectric properties of the canopies constituents Keywords: Path loss; Radio Propagation; Residential Trees; Specific Attenuation Coefficient; VHF; DOI : 10.7176/APTA/83-11 Publication date: December 30 th 2020
Highlights
Tree planting in residential environment is encouraged by government and non-governmental agencies, considering the social, environmental and economic importance in terms of oxygen provision and quality of air improvement, climatic amelioration, water conservation and soon
Efforts have been made by some radio researchers such as [1], [2], [3] and [4] to estimate the influence of tree canopy on radio waves propagation experimentally, and observations show that the scattering of radio waves from trees which are commonly found in residential environment is an important radio propagation mechanism
The need for further investigation of the effects of tree canopy on radio waves propagation at Ultra High Frequency (UHF) and at Very High Frequency (VHF) as these two frequency are well applied in radio wave broadcast
Summary
Tree planting in residential environment is encouraged by government and non-governmental agencies, considering the social, environmental and economic importance in terms of oxygen provision and quality of air improvement, climatic amelioration, water conservation and soon. 2. Theory Vegetation is one of the significant features that affect radio wave propagation, it attenuates radio signal exponentially by scattering, diffraction and absorption through it irregular structure of leaves and branches. The scattering of electromagnetic waves by systems whose individual dimensions are small compared with a wavelength is a common and important occurrence In such interaction it is convenient to think of the incident fields as inducing electric and magnetic multipoles that oscillate in definite phase relationship with the incident wave and radiate energy in directions other than the direction of incidence. Coherent field inside the canopy is governed by the propagation constant given by[10] as;. The average value of m obtained from each tree canopy was used to determine the permittivity of branches. After obtaining the required data from both Mango and Jathropha canopies experimentally, appropriate substitutions were made to equations 7, 8, 9, 10 and 11 and the results obtained were further substituted to equation 6 to obtain each canopy components of attenuation propagation constant k which was used to determine specific attenuation caused by each canopy constituents (Table 1& 2)
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