Optimization of radio communication in media with three layers

Abstract

Derived from an early National Bureau of Standards (NBS) tropospheric transhorizon propaption data base [I), a particular loss term defined as path attenuation was used in the radar equation to estimate the behavior of signal-to-noise ratio with frequency (10 to 1000 MHz) and distance (SO to 1000 km) including median and I, 10, 90, 99 percent variability. This loss term depends on frequency, distance, climate, r~fractivity and an empirically derived attenuation function which takes into account effects of antenna heights. Equivalent antenna temperatures are assumed to be due to plactic noise. Receiver noise is characterized by noise figure. For conveniently chosen system parameters (I MW transmitter power, I Hz receiver bandwidth, antenn;~ gains G, = G, = 1000), signal-to-noise ratio behavior is illustrated for several target cross sections (e.g. resonant dipole, conducting sphere) as a function of frequency, distance, variability for particular climates. Conversion to other system parameter values is straightforward. The complete details are available from the author [2].

Study of Propagation Loss Prediction in Forest Environment

“…The representation of the forest as a "dissipative dielectric slab" [9][10][11][12][13][14] becomes poor for frequencies above 200 MHz where the vegetation cannot be regarded as a homogeneous medium, since the dimensions of the vegetation is at a magnitude of an order of the wavelength [11]. After successfully examining the abovementioned three-layered model using the dyadic Green's function in [13], Cavalcante et al then proposed a four-layered (air layer, canopy layer, trunk layer and ground layer) model in [15] to take into account the vertical non-homogeneities of the forests with the lateral wave mode for propagation when the frequency is above 200 MHz (mainly in UHF).…”

“…After successfully examining the abovementioned three-layered model using the dyadic Green's function in [13], Cavalcante et al then proposed a four-layered (air layer, canopy layer, trunk layer and ground layer) model in [15] to take into account the vertical non-homogeneities of the forests with the lateral wave mode for propagation when the frequency is above 200 MHz (mainly in UHF). In their work, two isotropic and homogeneous dielectric layers placed over a semi-infinite ground plane are used to represent the tree canopy and the tree trunk layers of a forest.…”

Numerical Modeling and Mechanism Analysis of VHF Wave Propagation in Forested Environments Using the Equivalent Slab Model

“…Therefore, understanding the propagation mechanisms through a forest is critical for communication and sensing in such environments. Researchers have proposed different models to incorporate the forest characteristics and explain the observed forest propagation phenomena [1][2][3][4][5][6][7][8][9][10][11][12]. The most well accepted propagation model for frequencies in the HF/VHF ranges is the equivalent slab model.…”

“…In the original work of Tamir, only the forestair interface was considered. Subsequently, the three-layer isotropic slab model for air, forest and ground was used to describe the forest environment [2][3][4][5][6][7]. By further modeling the forest as a canopy layer and a trunk layer, Li et al [10] provided the solution to a four-layer anisotropic slab model.…”

Eigenfunctional representation of dyadic Green's functions in multilayered gyrotropic chiral media

“…DGFs play an important role in solving both source-free and source-incorporated boundary value problems and in characterizing macroscopic performance of multilayered complex media [20,[25][26][27], and some special transformations dealing with the scattering and radiation phenomena are also proposed by Li et al in [28]. Nowadays, the dyadic Green's function technique has been an important method employed elsewhere for boundary value problems [29], such as in Method of Moments and Boundary Element Method.…”