Control & Monitoring - Ground Station Design

 

In these tutorials we will look at the various component parts that make up a satellite ground station and the typical practices that engineers employ during satellite ground station engineering projects.

 

System Control and Monitoring

Antenna Control Unit (ACU)
In order to control the antenna tracking system, the antenna control unit (ACU) provides a user interface to the antenna positioning system. Satellite position data can be entered into the ACU and a satellite chosen for the antenna to be pointed at. The antenna will then move to the correct angles of elevation and azimuth to point at the satellite. A downlink signal is then used to track the satellite to ensure the antenna remains accurately pointed at all times.

Digital Tracking Receiver (DTR)
Used to receive and monitor the level of a chosen downlink signal the Digital Tracking Receiver provides an output to the ACU which indicates if the signal level is rising or falling or remaining constant. This is usually a DC voltage that is proportional to the signal level received.

Beacon Receiver
Similar to the DTR, the beacon receiver is designed to receive satellite beacons which are transmitted from the satellite to earth to allow antennas to locate and track them. The beacon receiver does essentially the same thing as the digital tracking receiver except with satellite beacon signals.

Time and Frequency Reference
In order to have accurate frequency conversion the up and down converters and sometimes the HPA and LNA/LNB can be connected to a highly stable and accurate frequency reference signal. The frequency reference is usually 5 or 10 MHz and is used to lock the local oscillator is the converters to provide reliable and stable frequency conversion. These time and frequency references can also be used to provide accurate time of day which some modems require for operation and in order to do this often have GPS satellite inputs. A GPS antenna is connected to the units which then provides the accurate time of day.

Monitoring and Control System (M&C)
To provide the users or maintenance staff with an overview of the system status an M&C system is used that is connected to every configurable piece of equipment in the antenna system. This then not only provides access to the status of each item of equipment but also allows remote control of the equipment from a location such as the site control room rather than at the antenna. The M&C system can also be used at the antenna shelter to access information and control equipment for test and maintenance purposes.

Keyboard, Video and Mouse (KVM)
In a rack mounted equipment room the M&C computer is also rack mounted and so the keyboard, video display monitor and mouse need to be rack mounted as well. Rack mounted slide out drawer units contain the keyboard, monitor and touch pad mouse that can be used to access the M&C locally.

In the next Tutorial we will look at Measurement & Test Equipment.