초록
Lately, there is a trend in the digital satellite communication
systeHs for private communication services of using the higher frequency
of Ku-band or Ka-bnad, and of using the narrower signal transmission
bandwidth. It therefore becomes very important to include the phase
noise effects in eNactly evaluating the performance of such digital
satell ite communication systems, because the phase noise becomes a
critical factor restricting the overal 1 performance of digi tai comm-
unication systems- The dominant components of the phase noises are known
to come from the local oscillators used in the transmitter and the
receiver of a ground station, and in satellite repeater. This disserta-
tion analyzes intensively how such phase noise 1 imits the performance of
the digital satellite communication Bystems, and proposes the perform-
ance prediction that can be achieved wi th the phase noises given.
The major noise sources in the satel 1 ite communication are assumed in
this research to be the thermal noise and the phase noise from the local
oscil taters, and they are special Iy model led to approwimate the noise
characteristics of the satell ite communication systems which include the
upl ink and downl ink cascaded after another. The system parameters taken
into account in the model are frequencies, gains, losses, thermal
background noi ses, and phase noi sos.
Based on the model , the noise performances are analyzed in terms of
f/H) ‥‥‥ The analytical results are then compared with the results
obtained by the commercial simulator EEsof. It is found in the compari-
sons that the analytical results coincide with the simulation results
within about 0. IdB even for the worst case, showing that the analytical
formula could be used to evaluate the system performance.
The more detailed analyses give rise to the system performance
evaluations in terms of the transmission bandwidth, f/fv, PLL bandwidth
and the phase noise levels. The important findings of the performance
analyses can be suHmarized as fol lows :
1) As the transmission bandwidth becomes narrower than 64kHz with the
increased CffV, the influence of the phase noise effects more
dominantly on degrading the overal 1 system performance seriously.
2) Taking only account of the phase noise, Bt/Bn = 0.005 " 0.01 can
be recommendable to minimize the phase error of the PLL when applying
the speci fications of fESS 30a/309 for an earth station and the speci fi -
cations of KOREASAT for a satellite.These results provide the useful bases in selecting the noise
bandwidth of PLL as wet 1 as deciding the required speci fication of phase
noise in the design of digital satel 1 ite communication systems.
It is also believed that the results will provide valuable aid for
those who are to design the digital satel 1 ite communication systems and
te speci fy the phase noise spectrum of the system
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