GPS over fibre system for antenna cable extension

Extend the reach of an antenna feeder cable up to 10Km, and overcome the limitations of a coaxial cable system.

Background

To provide an input signal to a GPS repeater, or a device such as a Network Time Sychronization unit, an outdoor antenna would ideally be installed at the highest point on the outside of the building.

The length of the coaxial cable from antenna to repeater/receiver may have an adverse effect on signal strength and quality.

GPS repeater in a police station ensures communications devices are always visible at the control centre

Coaxial cable limitations

  • In-line amplifiers and up-rated cable can be used to overcome signal losses caused by attenuation but may introduce unwanted noise and distortion.
  • Low-loss cable is often several millimetres in diameter (RF400 is ~11mm outer diameter) and is heavy and difficult to install over long distances.
  • Good quality low-loss coaxial cable can be expensive.
  • Even when using well-screened cable, signal can be affected by electromagnetic interference (EMI), especially if it is positioned near power lines.
  • Coaxial cables can be adversely affected by temperature changes, severe weather (especially lightning) and moisture.

Any, or all, of these factors may mean that it becomes impractical continually to increase the cable length.

GPS over fibre – a reliable and practical alternative

A point-to-point optical link consists of three main components:

RF-to-optical (TX) module – converts RF signals from the outdoor antenna into light pulses and transmits them down the optical fiber link.

Single mode optical fibre – SC/APC connectors (optionally FC/APC)

Optical-to-RF (RX) module – converts the light pulses back into RF signals and passes them to the GPS equipment (repeater | receiver | timing module).

Key features:

  • All GNSS GPS frequencies passed (1000 to 1800 MHz)
  • The transmit module provides a DC voltage to the low noise amplifier (LNA) in the GPS antenna
  • The receive module terminates the DC voltage output from the GPS repeater/receiver and presents an impedance that simulates the presence of a GPS antenna
  • Standard optical connector type is SC/APC (FC/APC on request)
  • Power for each unit is provided by an external +12V power adapter
  • Both TX and Rx units can provide connections for serial data transmission (RS232, RS485 & TTL) for monitoring and control

GPS over fibre system customised to your requirements

A typical system, as supplied to many FalTech GPS customers, consists of the following:

  • GNSS active antenna (Tallysman TW3742; 40dB gain)
  • 10m RF240 low-loss coax to connect antenna to TX unit
  • ViaLiteHD Blue OEM TX module with PSU
  • Pre-terminated optical fibre cable
  • ViaLiteHD Blue OEM RX module with PSU
  • 10m RF240 low-loss coax to RX unit to GPS repeater/receiver

Ask FalTech to help with a solution designed to meet your specific requirements


GPS over fibre systems

Available as a complete solution, including

  • antenna with mount
  • coaxial cables
  • fibre optic cable
  • optical units

Or the optical units can be supplied separately.

Contact FalTech to discuss your requirements  – details below.

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Contact FalTech

FalTech Limited,
6A Waterside House,
Falmouth Road,
Penryn,
Cornwall,
TR10 8BE, United Kingdom.
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