Handbook of Propagation Effects for Vehicular and ... - Courses

3-14
3.4.3 Austin, Texas at K-Band
Propagation Effects for Vehicular and Personal Mobile Satellite Systems
In Figure 3-12 is shown a K-Band (20 GHz) distribution (elevation angle = 55°) for an
approximate 10 km run along an evergreen (Loblolly Pine) tree-lined road in Bastrop,
Texas derived from the ACTS campaign. This distribution corresponds to the fade timeseries
plot in Figure 3-3 and was alluded to in Section 3.2. The Earth-satellite paths cut
the line of roadside trees on average at an angle of 57°. The population of trees was in
excess of 55%, and there were considerable segments of road where the trees formed a
tunnel with branches and foliage overhead. Also shown plotted is the EERS model
(dashed curve). We note that the EERS model underestimates the fade by at most 5 dB
for probabilities between 1% and 20%. This deviation is within the variability expected
in comparing the EERS model with measured distributions as exemplified for L-Band in
Figure 3-10. The underestimation of the EERS model at the smaller probabilities is most
likely caused by the prevalence of foliage tunnels giving a greater likelihood of fading at
the higher elevation angles.
Percentage of Distance Fade > Abscissa
100
9
8
7
6
5
4
3
2
10
9
8
7
6
5
1
4
3
2
Distribution Type
Bastrop Run (Extreme Shadowing)
EERS
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
Fade Depth (dB)
Figure 3-12: Distribution (solid) from ACTS 20 GHz measurements made in Bastrop,
Texas at an elevation angle of 54.5°. The dashed curve represents the corresponding
EERS model.