Satellite TV Distribution Systems: A Comprehensive Guide
Satellite TV Distribution: From Antenna to User
Satellite TV distribution (FI) delivers all channels broadcasted by a satellite to each user in a community. This system uses a satellite TV receiver (IRD) to convert satellite signals into watchable channels, allowing targeted access for interested users.
Types of FI Installations
Community FI Facilities
In line with ICT standards, community FI facilities utilize two chutes to distribute two different polarities, enabling all users to receive a designated group of channels.
Multicore Pooled Facilities
This system closely resembles an individual setup. It employs a switching system to share catchment systems, like the head amplifier, to distribute power independently to each user across all bands.
Collective Processor Facilities
This setup mixes signals from different satellites by positioning specific satellite transponders. This allows for a combined signal from multiple satellites, resulting in a single descent line.
Benefits:
- Cost-effective headend equipment
- Distribution of numerous channels
- Utilization of a wide bandwidth (47-1950 or 2150 MHz)
- Future-proof installation for receiving new channels
Disadvantages:
- Requires a separate satellite receiver for each TV
- Incompatibility with existing housing facilities
- Susceptibility to driver quality issues
FI Distribution Types
- Single Polarity Distribution: Receives signals from a single satellite.
- Multiple Polarity Distribution: Receives signals from two or more satellites.
Elements of a Single Polarity FI Distribution:
- Amplifiers
- Splitters
- Line Amplifiers
- Combiners
- Drifters
Elements of a Multiple Polarity FI Distribution:
- FI Processors
- Amplifiers
- Switchable H/V Splitters
- H/V Switches
- Passive Splitters
Note: Only one drop cable is used to distribute both MATV and satellite signals.
FI Processors
FI processors optimize bandwidth by delivering a full band of channels from a specific satellite and polarity through a single cable. These devices convert any satellite channel within a given band and polarity to another channel within a chosen IF band.
Key Features:
- Selection and management of desired satellite channels within the bandwidth
- Channel relocation within the same IF band
- Placement of processed channels onto unused direct distribution channels
Selection Criteria:
- Agility: Adaptability to various satellite channels
- LNB Powering: Ability to be powered through the LNB
- Low Phase Noise: Suitable for digital TV standards (e.g., >75dB at 10kHz)
- Conversion Flexibility: No limitations on input and output channel selection, including identical channels
- Low Spurious Emissions: Enables unrestricted signal mixing
Technical Specifications:
- Input and output frequency range
- Channel bandwidth
- Noise figure
- Input level
- LNB power
- Conversion limitations
- Phase noise conversion
- Spurious emissions
Amplifier Characteristics
Frequency:
Satellite IF band: 950-2150 MHz
Noise Figure:
Contribution of noise within the satellite IF band
EQ:
Should be around 10-12 dB
Maximum Output Voltage:
Capacity to handle a large number of channels (e.g., 115 dBµV)
Loss of Mixing with Terrestrial Signals:
Minimize signal degradation when combining with terrestrial signals
Amplifier Selection:
- Prioritize output voltage and noise figure
- Consider configuration capabilities and mixing losses
Combiners
Combiners are TV-SAT mixers used to combine terrestrial and satellite signals without modifying the existing distribution network. They have separate inputs for terrestrial and satellite signals and a single output for the internal user network.
Switchable H/V Splitters
These splitters mix and distribute terrestrial TV signals with vertically and horizontally polarized signals from the dish’s outdoor unit. They feature three inputs (one for each polarity and one for terrestrial TV) and offer high rejection between polarities and low signal loss.
H/V Switches
H/V switches receive horizontally and vertically polarized signals from the corresponding outdoor units mounted on the antenna. They have two inputs (one for each polarity) and a single output that can carry either polarity based on the voltage supplied by the indoor unit. These switches operate within a 47-2150 MHz bandwidth, allowing terrestrial channel signals to pass through unimpeded.
Pooled Transmodulation Facilities
These facilities utilize header receivers to demodulate satellite channels and deliver them to users as analog broadcasts. This eliminates the need for individual receivers in each home.
Transmodulation
Transmodulation involves demodulating a received signal and remodulating it into a different format.
Types of Transmodulators:
- QPSK-to-QAM Transmodulators: Convert original satellite broadcasts to QAM for efficient spectrum usage. Requires a QAM receiver.
- Analog-to-Analog (FM-PAL) Transmodulators: Demodulate satellite signals and remodulate them into PAL format for compatibility with analog TVs.
- Digital-to-Analog (QPSK-PAL) Transmodulators: Demodulate digital QPSK satellite signals and convert them to analog PAL format.
Designing TV Reception Facilities
Amplifiers:
Broadband amplifiers covering the entire satellite IF band (950-2150 MHz) are crucial for distributing a satellite band transparently to users.
Types of Amplifiers:
- Dual-Band Amplifiers: Amplify both terrestrial and satellite bands (47-2050 MHz). Used in large distribution networks.
- Dual-Band Amplifiers with Separate Satellite Amplifiers: Feature separate amplifiers for terrestrial and satellite signals, ensuring signal independence.
- Terrestrial Channel Equalizer Amplifiers with IF Band Amplification: Combine terrestrial channel equalization and satellite IF amplification in a single unit.
- Satellite Band Amplifiers: Specifically amplify the satellite IF band and often include band and polarity selection capabilities.
Amplifier Power Supply:
- Autonomous Amplifiers: Have integrated power supplies.
- Externally Powered Amplifiers: Require a separate power supply unit.