Propagation Factor and Path Loss Simulation Results for Two Rough Surface Reflection Coefficients Applied to the Microwave Ducting Propagation Over the Sea

Abstract

Abstract-The performance assessment of maritime microwave communications and radar systems requires accounting simultaneously for the non-homogeneous propagation medium over the sea and the rough sea surface scattering. The tropospheric ducting, specific for over water propagation, is one of the most difficult to treat propagation mechanisms. The proposed work combines a recently published in the literature phase correction, responsible for the shadowing effects, to the Ament rough surface reflection coefficient and the Parabolic Equation method (as implemented in the Advanced Propagation Model) to simulate the microwave propagation over the sea under evaporation duct conditions. Propagation factor and path loss results calculated for phase-corrected Ament, non-phase-corrected Ament and the other widely used, Miller-Brown, rough surface reflection coefficient are compared and discussed. The main effects from the accounting of the shadowing result in the shift of the interference minima and maxima of the propagation factor, changes in the path loss pattern and destruction of the trapping property of the duct.

Brief review on PE method application to propagation channel modeling in sea environment

“…Even though tentative, this study shows: a) the PL differences of scores of dB due to surface ducting will affect the link budget and increase the requirements to the WCDMA power control range; b) depending on the specific climatic characteristics, the use of annually averaged (and even seasonally averaged) values for the duct parameters, which is a common practice, may be not enough for accurate PL prediction. Searching to improve the propagation modeling and increase the agreement between predicted and measured fields, a number of authors have combined the PE (1) with different RRFs and applied it to simulate over-sea propagation in various scenarios [112][113][114][115]. As discussed in Section 2.2, some recently proposed RRFs account for the shadowing caused by the sea surface roughness on electromagnetic waves propagating under grazing incidence angles.…”

“…The physics behind this profile, based on the Monin-Obukhov similarity theory, is explained elsewhere [7,108,109]. As indicated by Paulus and Anderson [111], (20) is a good practical approximation to the average M( ) profile, and has been widely used as input to the PE propagation model applied under evaporation duct conditions [27,33,40,73,97,[111][112][113][114][115]. Equation (20), however, has been obtained assuming thermally neutral troposphere stratification and does not account for the tropospheric stability effects on the M profile [7,29,33].…”

“…Further comparisons between (14), (15), and (16) and their effects on the PF and PL for the case of ducted propagation over the sea are reported in [114,115]. (14) and (15)) the nce between the direct and reflected fields.…”

“…Thus it may be expected that the accounting for the shadowing will increase the destructive effect of the sea roughness on the duct structure trapping capability, especially as far as the long-range ducted propagation is concerned. Further comparisons between (14), (15), and (16) and their effects on the PF and PL for the case of ducted propagation over the sea are reported in [114,115]. Benhmammouch et al [112] studied the influence of the wind direction on electromagnetic waves propagation over rough sea surface by hybridizing two approaches to the sea surface representation: (i) the large sea surface roughness is generated on the basis of a sea spectrum multiplied by an angular spreading function, thus introducing the angle difference between the wind direction and electromagnetic wave propagation direction; (ii) the small roughness is introduced by replacing the standard deviation σ ξ in (14) with the standard deviation of capillarity waves.…”

Evaporation Duct Retrieval Using Changes in Radar Sea Clutter Power Versus Receiving Height

“…The pattern propagation factor accounts for the effect of refractivity structure M and the pattern function of the transmitting antenna. We model this factor using a parabolic equation (PE) method [30]. The final form of the PE [31,32] is…”