Attenuation Constants of Radio Waves in Lossy-Walled Rectangular Waveguides

Abstract

Abstract-At the ultra-high frequencies (UHF) common to portable radios, the mine tunnel acts as a dielectric waveguide, directing and absorbing energy as a radio signal propagates. Understanding radio propagation behavior in a dielectric waveguide is critical for designing reliable, optimized communication systems in an underground mine. One of the major parameters used to predict the power attenuation in lossy waveguides is the attenuation constant. In this paper, we theoretically and experimentally investigate the attenuation constants for a rectangular waveguide with dielectric walls. We provide a new derivation of the attenuation constant based on the classic Fresnel reflection coefficients. The new derivation takes advantage of ray representation of plane waves and provides more insight into understanding radio attenuation in tunnels. We also investigate the impact of different parameters on the attenuation constant, including the tunnel transverse dimensions, permittivity, conductivity, frequency, and polarization, with an aim to find their theoretical optimal values that result in the minimum power loss. Additionally, measurements of the attenuation constants of the dominant mode at different frequencies (455, 915, 2450, and 5800 MHz) for a straight concrete tunnel are presented and compared to theoretical predictions. It is shown that the analytical results match the measured results very well at all four frequencies.

Time Domain and Frequency Domain Deterministic Channel Modeling for Tunnel/Mining Environments

“…As a result, the source is equivalent to a large antenna array with theoretically an infinite number of elements located on the image plane. For a transmitter located at T ( x 0 , y 0 , 0), the received signal at an arbitrary location R ( x, y, z ) within the tunnel can be calculated as [4, 7, 20, 30]: $$E_r^y(x,y,z)=E_t\sum _{m=-\infty }^{+\infty }\sum _{n=-\infty }^{+\infty }\frac{e^{-{\mathit{jkr}}_{m,n}}}{r_{m,n}}{\rho }_{\perp }^{\mid m\mid }{\rho }_{false\Vert }^{\mid n\mid }$$ where the superscript “ y ” denotes a vertically polarized source. E t is a constant determined by the transmitted power.…”

“…(3), ρ ⊥ , || are the Fresnel reflection coefficients for the perpendicular and parallel polarizations, respectively. Under grazing incidences, the Fresnel reflection coefficients can be approximated as [20]…”

“…Given a transmitter location, the received electrical field (or power) at any location within a tunnel is obtained by summing up the contributions of all the rays that reach the receiver. The ray tracing method has been widely used for predicting indoor wireless transmission [18], evaluating field distribution in tunnels [19, 20] as well as hallways [21], and predicting delay spread in tunnel environments [22]. Depending on the way those rays that reach the receiver are identified, the ray tracing method can be divided into two categories—image-based ray tracing and shoot and bouncing ray (SBR) tracing.…”

“…Depending on the way those rays that reach the receiver are identified, the ray tracing method can be divided into two categories—image-based ray tracing and shoot and bouncing ray (SBR) tracing. The image-based ray tracing [4, 20] has a relatively low computation complexity, but its application is usually limited to environments with simple geometries. The SBR algorithm [23] can handle more complex environments (e.g., curved tunnels [24]) but requires significantly more computation resources and longer computation time.…”

Modeling the influence of wall roughness on tunnel propagation

“…As shown in [1], [7], the hybrid mode EH p,q can be viewed as an average of four plane waves (rays), each characterized by the following angles:…”