Promax HD Ranger +, Руководство пользователя

Страница: 142 / 224

December 2014
1
ANNEX 1 SIGNALS DESCRIPTION
A1.1
DIGITAL signals
A1.1.1
Digital TERRESTRIAL Television FIRST Generation
(DVB-T standard/COFDM modulation)
DVB-T Parameters
►
Channel Bandwidth
This parameter affects the frequency separation of the carriers. Its value
is 6 MHz, 7 MHz or 8 MHz.
►
Spectral inversion
It detects if the input signal has been inverted.
►
FFT Mode
It defines the number of modulation carriers between values 2k, 4k and
8k.
►
Guard Interval
This parameter is the dead time between symbols; its purpose is to detect
problems due to multipath echoes. This parameter is expressed in terms
of the symbol duration: 1/4, 1/8, 1/16, 1/32.
►
Constellation
Modulation used by the carriers. It also defines the noise immunity of the
system (QPSK, 16-QAM and 64-QAM).
►
Code rate
Also known as Viterbi ratio. It defines the ratio between the number of
data bits and the total number of bits transmitted (the difference
corresponds to the number of control bits for the detection and recovery
of errors).
►
TS Hierarchy
The DVB-T standard gives the possibility of TDT transmissions with
hierarchical levels, that is, the simultaneous transmission of the same
program with different image qualities and levels of protection to different
noises, so the receiver can switch to a signal of lesser quality when
reception conditions are not optimal.