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07-08/2014 —
TELE-audiovision International —
全球发行量最大的数字电视杂志
1. Satellite TV reception from a terrestrial
antenna. The principle behind MITRIS:
a terrestrial transmitter using satellite
frequencies
2. Typical infrastructure for MITRIS.
Content is streamed to a multiplexer and
then modulated to DVB-S/S2. Transmission
is made through omni-directional
terrestrial antennas, instead of uplinking
to a satellite. Reception, however is not
different from a traditional satellite TV. Just
point the dish to the transmitter antenna.
standard satellite broadcast.
The frequency band used by MITRIS
is also used for satellite reception. If
the antennas transmitting the MITRIS
signals are located too close to the sat-
ellite antennas disturbances can ocurr,
especially in high geographic latitudes
where the satellite antennas have a low
elevation.
A solution to overcome these prob-
lems is to install the MITRIS antennas
separate from the satellite antennas or
by making use of natural reflectors or
of intentionally putting up reflectors. In
any event, installing a MITRIS systems
requires careful planning to not disturb
satellite signals.
In exactly the same way that the
same frequency band from different
satellites can be used independently
from each other, MITRIS can also be
used without having to worry about dif-
ferent signals, i.e. satellite and/or MI-
TRIS interfering with each other.
This is a great way to utilize the limit-
ed availability of frequency bands mak-
ing MITRIS the ideal solution for TV dis-
tribution in rural areas and even more
so in mountaines regions with its many
natural obstacles which can be used fa-
vorably as a reflector to tune out unde-
grated Tele Radio Information System
and operates in the Ku-band satellite
frequency range. Another advantage
over the original MMDS is the output
transmission power used: it is lower
(less than 10 mW) with almost the
same coverage.
Because of this, MITRIS antenna
masts can be installed very close to
residents without incurring any of the
dxrawbacks that would result from
excessive radio waves. Naturally, this
simplifies the setup of MITRIS and si-
multaneously reduces the costs in-
volved since antennas can be mounted,
similar to mobile telephone services, on
existing structures.
With a bandwidth of 800 MHz, signifi-
cantly more channels can be broadcast
with MITRIS in the 11.7 to 12.5 GHz
frequency band since it has enough
room for up to 25 transponders. This
would yield an impressive 200 to 300
TV channels depending on the band-
width and modulation used.
It should be pointed out that MITRIS
does not transmit a polarized signal so
it doesn‘t matter if the LNB operates
in the horizontal or vertical position.
For this reason only half as many tran-
sponders are available compared to a
countries is only allotted a minimum
amount of bandwidth and the VHF/UHF
frequency bands are used for other
mobile services such as LTE.
The answer for some time has been
MMDS. This acronym stands for Multi-
channel Multipoint Distribution Service.
It has to do with terrestrial transmis-
sion in the 2.5 to 2.7 GHz frequency
range. 33 channels, each with 6 MHz
bandwidth can be transmitted (in the
USA it‘s only 31 channels) in this higher
frequency range. What‘s special about
this is the modulation of the digital
signal: just like with cable it‘s either
64QAM or 256QAM. But since there are
already other services in use in this
frequency band, MMDS was expanded
out of which came, among other things,
MITRIS.
MITRIS stands for Microwave Inte-
