Propagation Engineering in Wireless Communications by Abdollah Ghasemi Ali Abedi & Farshid Ghasemi

Author:Abdollah Ghasemi, Ali Abedi & Farshid Ghasemi
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

6.2.8 Multiple Isolated Obstacles

A number of authors have developed geometrical methods for modeling cascaded terrain obstructions as knife edges. Among them, the best one is known as Deygout model as illustrated in Fig. 6.11.

Fig. 6.11Radio path with multiple obstructions

This method is based upon finding the point on the profile which, treated as a single knife-edge obstruction for the whole path (ignoring all other points), gives the highest value of v. This is the principal point and in Fig. 6.11 is point B. The corresponding diffraction loss is calculated for T-B-R. The path is then divided into two parts, one on each side of the principal point, and the process is repeated. Assuming that the secondary principal points are at A and C, diffraction losses are calculated for T-A-B and B-C-R and added to the total. This process is recursive and can be continued until there are no further significant points. In practice, it is normal to limit the process using a suitable criterion.

Example 6.4.

Radiowave path profile is presented in Fig. 6.12. The heights of transmitter and receiver antennas are 2000 m and 2280 m, respectively, and the distance between them is 9.5 km. Calculate the diffraction loss of the obstacles for 150 MHz radiowaves. The obstacle heights are 2350 m and 2361 m, respectively.

Fig. 6.12Path profile for Example 6.4

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