AbstractMuch of the recent growth in microwave communication systems has occurred within urban areas. Private satellite and point to point microwave services have meant that microwave antennas are a common site on the roofs of offices. With the increase in system density comes the increase in the probability of mutual interference between systems sharing the same frequency band. However, the urban location of these systems means that there is also a greater possibility of a building obstructing the interference path, thus providing protection.
Because the introduction of microwave systems into an urban environment on such a scale is a relatively recent event, little information was available regarding the effect of a building on a radio path at microwave frequency. This thesis provides a procedure by which the diffracted field in the shadow of a building may be determined.
Diffraction models are developed based on Fresnel Integral methods and tested against results obtained from a measurement campaign conducted at a frequency of 11.2 GHz using real buildings as the diffracting obstacles. The diffraction model developed is extended from originally considering a two-dimensional great circle path to one which considers multiple path diffraction, typically via the roof and around the sides of the building.
It has therefore been possible to formulate procedures suitable for incorporation into CCIR recommendations whereby the presence of a building may be considered when determining coordination distance and evaluating practical interference threats on specific paths.
Finally methods by which the diffraction mechanism investigated may be incorporated into generalised signal strength prediction procedures that would consider other mechanisms, such as building scatter, are put forward.
|Date of Award||Sep 1993|