Page 131 - Satellite Communications, Fourth Edition

Radio Wave Propagation 111

From Eq. (4.8b):

a h b h a v b v
b c 5
2a c
0.0188 1.217 0.0168 1.2

2 0.0178
1.209
From Eq. (4.7):
b
c
A p a c R 01 L S r 01
0.0178 10 1.209 3.133 0.9178
0.828 dB

4.5 Other Propagation Impairments
Hail, ice, and snow have little effect on attenuation because of the low
water content. Ice can cause depolarization, described briefly in Chap. 5.
The attenuation resulting from clouds can be calculated as that for rain
(Ippolito, 1986, p. 56), although the attenuation is generally much less.
3
For example, at a frequency of 10 GHz and a water content of 0.25 g/m ,
the specific attenuation is about 0.05 dB/km and about 0.2 dB/km for a
3
water content of 2.5 g/m .

4.6 Problems and Exercises

4.1. With reference to Table 4.1, identify the propagation impairments which
most affect transmission in the C band.

4.2. Repeat Prob. 4.1 for Ku-band transmissions.

4.3. Calculate the approximate value of atmospheric attenuation for a satellite
transmission at 14 GHz, for which the angle of elevation of the earth-station
antenna is 15°.

4.4. Calculate the approximate value of atmospheric attenuation for a satellite
transmission at 6 GHz, for which the angle of elevation of the earth-station
antenna is 30°.

4.5. Describe the major effects the ionosphere has on the transmission of
satellite signals at frequencies of (a) 4 GHz and (b) 12 GHz.