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Wire and Wireless Communication Applications Chap. 8
TABLE 8–5 TYPICAL TVRO C-BAND SATELLITE AND RECEIVING SYSTEM †
Item
Parameter Value
Satellite
Orbit
Geostationary
Location (above equator)
134° W longitude
Uplink frequency band
6 GHz
Downlink frequency band
4 GHz
(P EIRP ) dBw 36 dBw
TVRO terminal
Site location
Washington, D.C., 38.8° N latitude, 77° W longitude
Antenna
Antenna type
10 ft diameter parabola
Noise temperature
32 K (at feed output) for 16.8° elevation
Feedline gain 0.98
Low-noise amplifier
Noise temperature
40 K
Gain
50 dB
Receiver
Noise temperature
2610 K
IF bandwidth
30 MHz
FM threshold
8 dB CNR
† Google “satellite footprints” and “satellite specifications” for current systems.
This TVRO terminal is typical of those used at the head end of CATV systems for reception of
TV signals that are relayed via satellite. As discussed in Sec. 8–5, the composite NTSC baseband
video signal is relayed via satellite by frequency-modulating this signal on a 6-GHz
carrier that is radiated to the satellite. The satellite down-converts the FM signal to 4 GHz and
retransmits this FM signal to the TVRO terminal.
The transmit antenna EIRP footprint for the satellite is shown in Fig. 8–25. From this
figure, it is seen that the EIRP directed toward Washington, D.C., is approximately 36 dBw, as
obtained for inclusion in Table 8–5.
It can be shown that the look angles of the TVRO antenna can be evaluated using the
following formulas [Davidoff, 1990]. The elevation of the TVRO antenna is
E = tan -1 c
1
tan b - R
(R + h) sin b d,
(8–48a)
where
b = cos -1 [ cos w cos l]
(8–48b)
and l-is the difference between the longitude of the TVRO site and the longitude of the substation
point (i.e., the point directly below the geostationary satellite along the equator). w is the latitude
of the TVRO site, R = 3963 statute miles is the Earth radius, and h = 22,242 statute miles is the
altitude of the synchronous satellite. The distance between the TVRO site and satellite, called the
slant range, is given by the cosine law: