Ground stations provide the interface to a wide variety of sources, cable, fiber optic, microwave, cellular, video, data, voice and other satellites. Simplified the station is broken down into it’s basic communications interface, baseband, Intermediate Frequency (IF) and Radio Frequency functional sections. I will address the basic breakdown of a ground station from a top level approach to the process used to provide links to and from a satellite or satellites.

For this example we will transmit a Ku-Band  Frequency Modulated carrier with a 46 MHz bandwidth at 14 GHz as the assigned frequency being transmitted at 100 watts of power. The corresponding receive signal will be 12 GHz at the same bandwidth of 46 MHz.

First you start with a building or small shelter. The equipment is installed to connect to the source to be transmitted, and the received information to it’s destination, this is the communications interface.  This is where the connections to data lines, cable connections, direct connections to a LAN, fiber optic connections,  and video feeds are made.

The data in it’s raw form is called a baseband signal, circuit, or line.  Single voice lines can be converted to multi-channel circuits, groups or trunks with baseband equipment and is referenced as multiplexing. Multiplexing can be preformed on voice, data and video signals using specific hardware for the type employed, Time Division Multiplexing (TDM) is one example.  In turn the receive signals will require de-multiplexing. The source may arrive as a multiplexed signal and not require this processing. Signal levels are set or adjusted at the baseband stage to meet the input requirements of the next section.

The baseband signals are then passed to the Intermediate Frequency (IF) equipment where the raw (baseband signal) is modulated onto a carrier frequency. Types of modulation used are based on the signals used, common types are FM, PM, TDMA, BPSK, and QPSK. For the purpose of discussion we are using a 70 MHz carrier and Frequency Modulate (FM) it with the data. Through the modulation process the 70 MHZ carrier will deviate +/- from the center frequency and simply put the measured result is the bandwidth of the carrier, it is set or adjusted in the modulator.  The output of the modulator in this case is then called a 70MHz carrier and is adjusted to a 46 MHz bandwidth at the proper input level to be applied to the next stage.

Following IF conversion the carrier is passed to the Radio Frequency (RF) equipment. At the RF stage the carrier frequency is converted from a 70 MHz carrier to the selected transmit frequency 14 GHz carrier using an up converter. The resulting output is a carrier at 14 GHz at the same bandwidth set in the IF stage. The carrier is then passed to an intermediate amplifier to control the output level of the carrier by setting the drive level for the input to the high power amplifier stage to achieve the 100 watts output. High power amplifiers are the transmitter and are connected to the transmit port of the antenna.

The satellite receives the antennas transmitted carrier from the ground, translates the frequency to the down-link frequency to prevent interference between the transmit and receive frequencies and sends it back to the ground.

The antenna now receives the carrier from the satellite at the receive frequency of 12 GHz. Low Noise Amplifiers (LNA) are used to compensate for transmission losses to the ground. The output from the LNA is sent to a down-converter to convert the 12 GHz carrier back to a FM modulated 70 MHz IF carrier and adjusted to the input level for the receiver.

Back at the IF receive stage the 70 MHz carrier is removed in the receiver by the corresponding demodulator to produce the baseband signals or data. These baseband receive signals are either de-multiplexed or passed directly back to the communications interface.  Where the connections to data lines, cable connections, direct connections to a LAN, fiber optic connections,  and video feeds are made.

To minimize the chances of equipment failure and extend the operational life of the hardware, it can be installed in rooms that are both temperature and humidity controlled. Commercial power outages can cause significant loss of revenue. To prevent or minimize power outages  uninterrupted power systems (battery backup) called UPS and generators are installed for use when commercial power is not available.