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

12-14
Standard Deviation (dB)
4
3
2
1
0
Propagation Effects for Vehicular and Personal Mobile Satellite Systems
Average Case
Best Case
2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9
1 10 100
Bandwidth (MHz)
Figure 12-6: Standard deviation of signal fading versus-Bandwidth for UHF to L-Band
frequencies for inside building measurements
12.8.4 Fading Effects Due to Antenna Positioning
The median antenna displacement giving minimum and maximum signal levels was
found to be between 35 and 45 cm independent of frequency between 0.7 and 1.8 GHz.
Differences in signal levels between the values at maximum and minimum locations have
been noted to be as high as 30 dB. These distances are suggested antenna spacing values
for diversity gain operation.
12.8.5 Effects Caused by the Human Body
A person blocking the transmission may cause fades between 6 to 10 dB in the frequency
interval of 700 to 1800 MHz. People moving near the receiving antenna but outside the
antenna Fresnel region typically produce variations of less than 0.5 dB. A hand-held
terminal at 900 MHz may result in a signal decrease of 4 to 7 dB when held at the waist
and 1 to 2 dB when held against the head.
12.8.6 Suggestions for Further Work
Analysis of the type described in the chapter should be carried out at frequencies above
3 GHz.