Microwave/millimeter-wave propagation in woods and forests was investigated at 9.6, 28.8, and 57.6 GHz. The experiments were repeated over the same transmission paths, under both summer and winter conditions, i.e. with tree in leaf and without leaves. Of particular interest were the range dependence, beam broadening, and depolarization of millimeter-wave beams in vegetation and frequency dependence of these effects. The experiments have shown, in particular, that the range dependence is characterized by a high attenuation rate at short vegetation depths and a reduced attenuation rate at large depth. For trees fully in leaf, the transition between the two regimes can be abrupt and the change in attenuation rate substantial. Just after the transition significant beam broadening (and depolarization) occurs. A theory of millimeter-wave propagation in vegetation was derived using transport theory. >

Millimeter-wave propagation in vegetation: experiments and theory

In this paper, a large number of studies of the efiect of the foliage on single or lines of trees on modern wireless communication systems are reviewed. The paper is focused on the experimental works mainly done for commercial applications such as cellular communication and high speed point-to-point flxed link at the microwave and millimeter wave frequencies. For this review study, the development of the foliage loss prediction methods and the factors in∞uencing the tree-induced shadowing efiect are highlighted. In view of current research work in this area, some possible future works are proposed to improve the performance of modern wireless communication systems with the efiect of foliage.

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Investigations of foliage effect on modern wireless communication systems: a review

A 35-GHz bistatic radar system was used to measure the attenuation through trees and the bistatic scattering pattern of tree foilage. The data were found to be in good agreement with a first-order multiple scattering model. Measurements were also made to study the angular vibration of the bistatic scattering coefficient of a smooth sand surface, a rough sand surface, and a gravel surface. The measurements, which were made for HH, HV (horizontal transmit, verticle receive), and VV polarization configurations over a wide range of the azimuth angle and the scattering angle, provide a quantitative reference for the design and use of millimeter-wave bistatic radar systems. >

Millimeter-wave bistatic scattering from ground and vegetation targets

https://researchportal.port.ac.uk/portal/files/3217937/Wireless_sensor_network_coverage_measurement.pdf

Wireless sensor network coverage measurement and planning in mixed crop farming

As wireless communication moves from long to short ranges with considerably lower antenna heights, the need to understand and be able to predict the impact of vegetation on coverage and quality of wireless services has become very important. This paper focuses on vegetation attenuation measurements for frequencies in the range 0.4{7.2GHz in mango and oil palm plantations to evaluate vegetation attenuation models for application in wireless sensor network planning and deployment in precision agriculture. Although a number of models have been proposed and evaluated for speciflc frequencies, results show that these models do not perform well when applied to difierent vegetation types or at difierent frequencies. A global assessment of the models using a broad range of frequencies shows that the COST 235 model gives more consistent results when there is vegetation in the propagation path. For grid-like plantation, the study shows that the RET model provides the best prediction of path loss for measurements between two rows of trees. However, taking into account

/pdf/vegetation-attenuation-measurements-and-modeling-in-3b5z7wk7ga.pdf

Vegetation attenuation measurements and modeling in plantations for wireless sensor network planning

: A theory of mm wave propagation in woods and forests is presented which models the vegetation environment as a statistically homogeneous random medium of scatterers characterized by a scatter function (phase function) with a narrow forward lobe and an omnidirectional background The model describes the medium in terms of four overall theoretical parameters whose numerical values can be determined in principle by comparison of analytical results and experimental data The scalar transport theory is used to determine the coherent and incoherent field intensities in the forest medium; the problem solved is that of a vegetation halfspace illuminated by a plane wave Formulas and graphs are presented on the range dependence of the coherent and incoherent intensities, and on the angular spectrum (beam broadening) of the incoherent intensity Comparison with experimental results obtained by an independent investigation has shown good qualitative agreement of calculated and measured results Originator-supplied keywords include: Millimeter wave propagation, RF propagation in woods/forests, terrain effects on millimeter wave transmission, Transport theory, Random media, Coherent and incoherent field components, and Range dependence and beambroadening of millimeter waves in vegetation

/pdf/a-transport-theory-of-millimeter-wave-propagation-in-woods-22iybtbp2o.pdf

R. A. Johnson

Papers

A transport theory of millimeter wave propagation in woods and forests