Results 251 to 260 of about 4,721 (271)

The transient response above an evaporation duct

Journal of Physics D: Applied Physics, 1998
The transient electromagnetic field generated by a vertical electric dipole above an evaporation duct is investigated theoretically. The evaporation duct model used is that previously described by Kahan and Eckart. A vertical electric dipole, above the surface layer, is taken as the source of the electromagnetic field. We determine the electrical field
openaire   +1 more source

The Impact of Evaporative Ducting on Covert Communications

MILCOM 2007 - IEEE Military Communications Conference, 2007
This paper provides a brief primer on tropospheric ducting and examines the potential impact that evaporative ducting has on the intercept vulnerability of covert communication systems. The study considers the intercept vulnerability of a generic ship-based satellite terminal in the presence of evaporative ducting when the threat consists of a total ...
openaire   +1 more source

Influence of evaporation ducts on radar sea return

IEE Proceedings F Radar and Signal Processing, 1990
Modelling of radar sea return is discussed with consideration of propagation conditions. Both the intensity and propagation direction of energy incident at the sea surface can be significantly affected by the refractive condition of the atmosphere. The authors describe and evaluate a model that incorporates both of these effects for the situation where
J.P. Reilly, G.D. Dockery
openaire   +1 more source

Practical application of an evaporation duct model

Radio Science, 1985
The application of an evaporation duct model in operational and climatological assessments of propagation and the sensitivity of the model to meteorological measurements are examined. The unexpectedly frequent occurrence of evaporation duct heights greater than 40 m is related to thermally stable conditions in the atmospheric surface layer.
openaire   +1 more source

Determination of evaporation duct heights by an inverse method

SPIE Proceedings, 2007
The detection and tracking of naval targets, including low RCS objects like inflatable boats requires a thorough knowledge of the propagation properties of the maritime boundary layer. Models are in existence, which allow a prediction of the propagation factor using the parabolic equation algorithm.
R. Douvenot, V. Fabbro, C. Bourlier, J. Saillard, H.-H. Fuchs, H. Essen, J. Förster   +6 more
openaire   +1 more source

94-GHz propagation in the evaporation duct

IEEE Transactions on Antennas and Propagation, 1990
One-way, low-altitude radio propagation measurements at 94 GHz and simultaneous surface meteorological measurements were made on a 40.6 km, over-horizon, over-water path along the southern California coast to assess the effects of the evaporation duct on signal propagation.
openaire   +1 more source

The research of radio wave propagation in the evaporation duct

2009 3rd IEEE International Symposium on Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications, 2009
In this paper, a valid and accurate method is presented that accounts for the characteristics of radio wave propagation in the evaporation duct using the Model method. The model assumes a trilinear refractivity profile and the layer to be stationary and horizontally homogeneous, using the model program calculations the height gain and path loss for ...
Miao Zhong, Chengguo Liu, Yang Li, Ming Yang   +3 more
openaire   +1 more source

Study on Wireless Detection in Condition of Evaporation Duct

2009 5th International Conference on Wireless Communications, Networking and Mobile Computing, 2009
Evaporation duct is a layer of air just above the sea surface which can trap wireless energy. It is created by the rapid decrease of humidity with height just above the sea surface. Owing to it, the path of wireless wave is changed remarkably, the wireless detection range will be increased to realize the phenomenon of OTH (over-the-horizon) detection ...
Bin Tian, Hao Cha, Jie Li, Mo Zhou
openaire   +1 more source

Propagation Theory for the Evaporation Duct

1973
Propagation in radio ducts first attracted attention during the 1940’s and was the subjectof some notable theoretical studies (1),(2),(3).Recent developments such as the use of the Monin-Obukhov similarity theory(4) to give realistic refractive index models, improvements in theoretical and numerical methods and the need to incorporate other phenomena ...
openaire   +1 more source

Investigations into the occurrence of evaporation ducts near Karachi

2017 International Conference on Communication Technologies (ComTech), 2017
Refraction through the atmosphere is one of the propagation mechanisms of wireless signals traversing the atmosphere. Different refractive conditions can be prevalent at a particular place, height and time, depending on the weather conditions. Ducting and sub-refractive conditions can lead to Anomalous Propagation (ANAPROP).
Saeed Ur Rehman, Naveed Mufti
openaire   +1 more source