UNIT 04 EARTH SEGEMENT CONTENTS – chapter 8 OF TXT
Introduction receive only home TV system outdoor unit indoor unit M AT V, CATV Tx–Rx earth station. Topic on 5-11-2020
Introduction receive only home TV system INTRODUCTION
The earth segment of satellite communication system mainly consists of two earth stations. ... The transmitting earth station transmits the information signals to satellite. Whereas, the receiving earth station receives the information signals from satellite. Type of Earth Station Depends on
Function of the station Type of Service Frequency band used Tx and Rx Characteristics Antenna Characteristics Topic on 7-11-2020
Receive only home tv system Outdoor unit Indoor unit Receive only home tv system
Ku (12-GHz) band direct broadcast satellite (DBS) service Variations could be there Sometimes C Band 4 GHz though not intended Some manufacturers provide dual C-band/Ku-band equipment mesh type reflector dual feedhorn Much of television programming originates as first generation signals, also known as master broadcast quality signals Advantages C-band equipment for home reception is that there is no loss of quality compared with the compressed digital signals. Multiple satellites Polar Mount
Most widely advertised receiving system for C-band system appears
DigiCipher 2 is the name given to the digital compression standard used in digital transmissions DigiCipher 2
DigiCipher 2, or simply DCII, is a proprietary standard format of digital signal transmission and it doubles as an encryption standard with MPEG-2/MPEG-4 signal video compression used on many communications satellite television and audio signals. The DCII standard was originally developed in 1997 by General Instrument, which then became the Home and Network Mobility division of Motorola, then bought by Google in Aug 2011, and lastly became the Home portion of the division to Arris
DigiCipher II uses QPSK and BPSK at the same time Compression and Scrambling
VideoCipher brand name for the equipment used to scramble analog TV signals DigiCipher 2 is the name given to the digital compression standard used in digital transmissions So how Differentiate Ku and C band? FREQUENCY OF OPERATION OF THE OUTDOOR UNIT SATELLITES INTENDED FOR DBS HAVE MUCH HIGHER EQUIVALENT ISOTROPIC RADIATED POWER (EIRP) – (ie Ku band) C band more larger systems and huge antenna sizes The outdoor unit
Receiving antenna feeding directly into a low-noise amplifier/converter combination A parabolic reflector Horn mounted at the focus Reflector diameters in the range 0.6 to 1.6 m Reflector diameter for 4-GHz reception can range from 1.83 m (6 ft) to 3 m (10 ft). the gain of a parabolic dish is proportional to (D/ )2
Although the free-space losses are much higher atλ 12 GHz compared with 4 GHz, a higher-gain receiving antenna is not needed because the DBS operate at a much higher EIRP, The outdoor unit
The downlink frequency band of 12.2 to 12.7 GHz spans a range of 500 MHz which accommodates 32 TV/FM channels Each 24-MHz wide To reduce interference Polarization interleaving
left-hand circular (LHC)
right-hand circular (RHC) or vertical/horizontal
LNB – Low Noise Block – LNA +LNC.
The indoor unit
Signal fed Wideband Signal 950 -1450MHz Amplify transmit to tracking filter , ? sel desired channel Due to polarization interleaving only ½ of 32channels Since channels are separated by polarization, job of tracking filter is easy Again frequency conversion to IF range -70MHz 70MHz or other VHF used DBS uses FM Normal TV uses AM –VSB
MATV
Small group of users The advantage Only one outdoor
Separate lna/cs and feeder cables are required for each sense of polarization.
Compared with the single user system, a larger antenna is also required
(2- to 3-m diameter) in order to maintain a good signal-to-noise ratio MATV Types of LNA (only for your reference) Advantages
Only 1 Outdoor Unit Feeds no of indoor unit separate LNA/Cs and feeder cables are required for each sense of polarization. CATV - Community Antenna TV System CATV
The CATV system employs a single outdoor unit, with separate feeds available for each sense of polarization, like the MATV system Instead of having a separate receiver for each user, all the carriers are demodulated in a common receiver-filter system combined into a standard multiplexed signal for transmission over cable to the subscribers. With the CATV system, local programming material also may be distributed to subscribers, an option which is not permitted in the MATV system Comparison CATV and MATV Contents on 19-11-2020
M AT V, CATV Recap Tx–Rx earth station Transmit-Receive Earth Stations Transmit-Receive Earth Stations
Receive only TV Only reception – outdoor –indoor units etc Wholeness Both Uplink and Downlink Includes Network TV Redundant Interconnection equipment from satellite station and terrestrial network Eg Considered Telephone Network Multiplexing group of 12 tel channels Multiplexed signal translated 70MHz IF After Amplification Upconverted Same carrier carry traffic to multiple destinations like kengeri and kadubessanahalli but have receiver filters that are different After upconversion combine wideband signal is amplified. Parameters to consider??
Then fed to antenna diplexer helps in TX and RX Simultaneously C band uplink —> 6 GHz Downlink 4 GHz Ku band uplink frequency 14 GHz, Downlink 12 GHz High GAIN & Narrow BEAM antenna prevent interference LNA divider network during reception
Classes of Earth station
Based on Traffic Heavy Route6/4-GHz heavy-route system, each satellite channel (bandwidth 36 MHz) is capable of carrying over 960 one-way voice circuits simultaneously or a single-color analog TV signal with associated audio Medium Route multiple access, either on the basis of frequency-division multiple access (FDMA) or time-division multiple access (TDMA), multiplexed baseband signals being carried in either case. Thin Route transponder channel (36 MHz) may be occupied by a number of single carriers, each associated with its own voice circuit. This mode of operation is known as single carrier per channel (SCPC) Antenna
Large Antenna -250 tons, Narrow Beam