Page 408 - Satellite Communications, Fourth Edition

388 Chapter Twelve

TABLE 12.3 ISL Frequency Bands
Frequency band, Available bandwidth,
GHz MHz Designation
22.55–23.55 1000 ISL-23
24.45–24.75 300 ISL-24
25.25–27.5 2250 ISL-25
32–33 1000 ISL-32
54.25–58.2 3950 ISL-56
59–64 5000 ISL-60
65–71 6000 ISL-67
116–134 18000 ISL-125
170–182 12000
185–190 5000
SOURCE: Morgan, 1999.

Antennas for the ISL are steerable and the beamwidths are sufficiently
broad to enable a tracking signal to be acquired to maintain alignment.
Table 12.4 gives some values for an ISL used in the Iridium system.

Example 12.21 Calculate the free-space loss for the ISL parameters tabulated in
Table 12.4. Given that the system margin for transmission loss is 1.8 dB, calcu-
late the received power.
Solution From Eq. (12.10):
[FSL] 32.4 20 log r 20 log f

3
32.4 20 log 4400 20 log(23.28 10 )
192.6 dB

TABLE 12.4 Iridium ISL
East-West ISL (without sun)
Frequency, GHz 23.28
Range, km 4400.0
Transmitter

Power, dBW 5.3
Antenna gain, dB 36.7
Circuit loss, dB 1.8
Pointing loss, dB 1.8
Receiver
Pointing loss, dB 1.8
Antenna gain, dB 36.7
Noise temperature, K 720.3
Noise bandwidth, dBHz 71
SOURCE: Motorola, 1992.