Calculate propagation in a hilly terrain using the empirical two-ray model (ETR).
Model Type
In this rural/suburban scenario, the geometry is described by topography (elevation)
and clutter/morpho (land usage). In the tree view, click
Topography to view the topography database or
Clutter/Morpho to view the land usage.Figure 1. The topography for the rural/suburban scenario.
Figure 2. The clutter/morpho (land usage) for the rural/suburban scenario.
Sites and Antennas
The topography contains two sites: Site 1 has two directional antennas at the height
of 25 m, and Site 2 has an omnidirectional antenna at a height of 50 m. Each antenna
operates at a single carrier frequency of 2000 MHz.
Tip: Click Project > Edit Project Parameter and click the Sites tab to view the sites
and antennas.
Computational Method
The empirical two-ray model (ETR) model computes the path loss to each
pixel based on the assumption that the direct ray and the ground-reflected ray
exist. There is no check if the rays exist or if they are shadowed, whereas in the
deterministic two ray model, rays are only considered if
they are not shadowed.
Knowing that the empirical two-ray model would be too optimistic
in shadow regions, a line-of-sight check is performed, and the two-ray model is
extended with knife-edge diffraction to handle such regions accurately.
Tip: Click Project > Edit Project Parameter and click the Computation tab to change
the model.
Results
Results are computed for each transmitter on a prediction plane of 1.5 m. Propagation
results include power coverage of each transmitting antenna, field strength, path
loss, and line-of-sight results for both sites. Figure 3 shows an example of
power coverage for Site 2 Antenna 1. The large dynamic range is obtained by the
addition of knife-edge diffraction for shadow regions. The knife-edge diffraction
ensures realistic results where no direct line of sight exists.
Figure 3. Power coverage of Site 1 Antenna 2. Note the large dynamic range. The
option of additional Knife-Edge Diffraction ensures realistic results where
no direct line of sight exists
