Understanding TV Signal Distribution Systems: A Comprehensive Guide

Posted on Aug 29, 2024 in Computers

Individual Antenna Facilities

Used to serve a single dwelling, these facilities capture signals strong enough for distribution within a limited distance (up to 50m). They handle signal mixing, separation, impedance matching, and amplification if needed.

Addressing Double Images and Signal Level Differences

When double images occur, the captured signal needs conversion to a non-adjacent channel. Signal level differences between channels at the user end should not exceed 12 dB.

Domestic Network Distribution

This preferred system utilizes a network of splitters with varying attenuation levels, ensuring optimal signal strength throughout the dwelling.

Internal Network with Step Attenuators

Suitable only for individual installations, this method uses step attenuators to compensate for signal loss. Equalized outlets with radio-TV separators ensure signal rejection between adjacent outlets.

Types of Outlets

  • Intermediate or Series Outlets: Inserted within the internal network.
  • Final Outlets: Used as the endpoint of the internal network, connecting directly to the user’s equipment.

Collective Facilities

Designed for buildings with multiple dwellings, these facilities provide each user with a dedicated internal circuit and a high-quality signal, while preventing interference between receivers.

Signal Distribution Network Components

  • Delivery Network: Connects the headend to the dispersion network.
  • Dispersion Network: Connects the distribution network to the PAU (Point of Access to the User).
  • PAU (Point of Access to the User): The entry point of the network into the user’s dwelling.
  • User Network (Dwelling): The distribution network within the user’s dwelling.
  • User Outlets: Connect the delivery network to the user’s equipment.

Signal Reception Devices

These devices demodulate, decode, and process the received signal.

Types of Signal Distribution Network Structures

  • Chained Outlets with Step Attenuators: Suitable for single-family dwellings, but not recommended for multi-dwelling buildings.
  • Star Network: Uses distributors to split the signal, well-balanced but requires more cabling. Recommended for installations with a small number of outlets (<16).
  • Tree or Branch Network: Widely used in collective or large individual installations, combining splitters and step attenuators. Optimizes cable usage and is suitable for a large number of outlets.
  • Combined Tree-Branch/Star Network: Recommended for medium to large installations, using splitters for distribution and a star configuration within the dwelling.
  • Multiswitch/Multithreaded Network: Designed for distributing satellite signals transparently, using switchable multiswitches.

Design Criteria for Distribution Networks

  • Balanced distribution
  • Support for the required frequency bands
  • Use of extended bandwidth networks (recommended)
  • Devices with a Return Loss of at least 6 dB in the satellite band
  • Thorough network calculations for all outlets and bands

Recommendations for Network Structure Selection

  • Star Network for detached houses with less than 16 outlets.
  • Tree-Branch/Star structure for multi-dwelling units with less than 6 outlets per dwelling.
  • Consider providing an outlet for each room, even though regulations may only require one per two rooms.

Choosing Network Elements

  • Select a network structure based on the installation type.
  • Choose appropriate elements based on manufacturer recommendations.
  • Estimate signal losses between the delivery network entry and user outlets.
  • Calculate the best and worst-case scenarios for signal strength and ensure acceptable differences between bands and outlets.

Types of Terrestrial TV Distribution Systems: MATV and SMATV

MATV (Master Antenna Television): Uses a single antenna system to serve multiple users, commonly used in collective facilities.

SMATV (Satellite Master Antenna Television): An extension of MATV that includes satellite services.

Classification of MATV and SMATV Facilities

  • By Market Type: Individual or collective facilities.
  • By Signal Configuration: Signals with similar levels that can be treated together, or signals requiring individual equalization.

Types of Satellite TV Distribution Systems

  • Individual Installations: Can be independent of, dependent on, or a new installation replacing an existing system.
  • Collective Installations: Typically utilize one of three distribution methods: IF distribution, S-band distribution, or transmodulation.

Individual Installation Types

  • Independent of Existing Installation: Uses an LNB that receives four polarities from a single orbital position, allowing for single-cable distribution.
  • Dependent on Existing Installation: Integrates with the existing conventional installation, but may require upgrades due to bandwidth requirements.
  • New Installation: Employs multi-polarity switchable distributors in a star configuration, offering flexibility and future-proofing.

Collective Installation Types

  • IF (Intermediate Frequency) Distribution: Distributes satellite signals in their original QPSK modulation. Various configurations exist for distributing single or multiple polarities.
  • S-Band Distribution: Limited capacity and largely obsolete.
  • Transmodulation: Converts satellite signals to terrestrial frequencies for distribution over existing coaxial cable networks.

IF Distribution Configurations

  • Single Polarity Distribution: Simple headend with an amplifier, but limited channel selection.
  • Two Polarity Distribution: Requires a dual distribution network, offering more channel options and flexibility.
  • Multi-Polarity Distribution (Multithreading): Allows users to access all channels from multiple satellite platforms, but requires more cabling and is less flexible.
  • Selective IF Distribution: Uses IF processors to select and distribute specific channels, optimizing bandwidth usage.

This comprehensive guide provides a detailed overview of TV signal distribution systems, covering various aspects from individual to collective installations, terrestrial to satellite TV, and different network structures and components. By understanding these concepts, you can make informed decisions when designing or upgrading your TV distribution system.