Transmitting Digital Television Signals by Satellite - DVB-S/S2 - Digital Video and Audio Broadcasting Technology - page 237

14 Transmitting Digital Television Signals by
Satellite DVBS/S2

Today, analog television signals are widely received by satellite since this
type of installation has become extremely simple and inexpensive. Thus, in
Europe, a simple satellite receiving system complete with dish, LNB and
receiver is available for less than 100 Euros and there are no follow-up ex-
penses. Similar importance must, therefore, be accorded to the distribution
of digital TV signals over the same transmission path. In the meantime,
analog satellite reception in Europe is being replaced more and more by
digital video broadcasting by satellite. In this chapter, the method of
transmitting MPEG-2 source encoded TV signals via satellite is described.

Ω F 1

Centrifugal force:

Satellite

r

Earth

F 1 = m Sat Ω 2 r ;

m Sat = mass of satellite;

Ω = 2 Π / T = angular speed;

Π = 3.141592654 = circular constant;

T = 1 day = 24 60 60 s = 86400 s ;

Fig. 14.1. Centrifugal force of a geostationary satellite

Every communication satellite is located geostationary (Figs. 14.1.,
14.2. and 14.3.) above the equator in an orbit of about 36000 km above the
Earth's surface. This means that these satellites are positioned in such a
way that they move around the Earth at the same speed as that with which
the Earth itself is rotating, i.e. once per day. There is precisely only one
orbital position, at a constant distance of about 36,000 km from the Earth's
surface, where this can be achieved, the only point at which the centrifugal