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

8-4
SIGNAL LEVEL (dB)
5
0
-5
-10
-15
-20
-25
-30
-35
Single Position
Minimum
Propagation Effects for Vehicular and Personal Mobile Satellite Systems
Maximum
700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800
FREQUENCY (MHz)
Figure 8-1: Maximum and minimum relative signal levels (thin lines) in a composite
vertical scan of 80 cm and frequency sweep over the indicated frequency interval for
Site 2. Thick curve corresponds to fixed receiver antenna versus frequency example
[Vogel and Torrence, 1993].
8.2.3 Time Delay Distributions
Through the execution of a Fast Fourier Transform of the signal level over the frequency
interval examined, estimates of maximum multipath time delays were derived.
Cumulative distributions of these time delays are given in Figure 8-2 for three different
site locations. It is clear from this figure that 90% of the power have delays smaller than
20 ns, 30 ns, and 80 ns for Sites 2, 4, and 3, respectively, and more than 99% of the
power have associated delays smaller than 100 ns for Sites 2 and 4. These results were
consistent with power loss measurements employing a series of bandwidths between 1
and 90 MHz over the frequency interval from 700 to 1800 MHz in that negligible
bandwidth dependence was found in the loss statistics results.