What is a Satellite Network?

A satellite network has a ground-based station that uses a transceiver to control it. The network also has ground stations for users to send and receive communication through the satellite system.

What is Satellite Communication, and How Does it Work?

A satellite is a device in space that can receive signals from Earth and send them back to the same place or a different location.

Satellite systems send data at high speeds of the GigaHertz level, are costly, and are often used by large companies or institutions. It saves distance and time for a company with branches at many points.

Components of a Satellite Network

Transponders

Transponder devices receive and send signals. They boost the signals before returning them to the ground and change the frequency to avoid interference.

Earth Stations

Ground stations control the satellite reception and regulate interconnection between terminals. It also manages the output channels, encodes the data, and controls the transfer rate. There are three receiving stations, an antenna, and a broadcast station.

1. Receiving station

The receiving station gets all the info from the transmitting station and sends it to the satellite.

2. Antenna

The antenna picks up the signal from the satellite and sends it to the feeder at the focal point. A good antenna can reduce interference and noise. Antennas have devices for receiving and transmitting.

By adjusting the antennas’ signal models, we can only cover one country’s area globally.

3. Broadcast Station

A broadcast station has a transmitter and antenna. It has the reliable power to send signals well. The antenna gets the call and sends it to the satellite with the proper modulation and carrier.

Air is the primary medium used for physical transmission without guidance. Microwave signals sent to satellites remain strong even when it’s raining. It can also be low or high frequency between 100 MHz and 10 GHz.

Satellite broadcasts have two parts: the bus and the payload. The bus controls how the payload works. The load carries the user’s information.

Satellite TV only sends signals one way. Sometimes, it’s essential to have one place that sends signals to a satellite. Additionally, many businesses receive calls from it.

Ground stations can send and receive signals for different types of two-way services. Small antennas and low-power transmitters can serve many users in satellite services.

Satellite Rise Model

The main component of a satellite system in the rise model is the ground station transmitter. A transmitter has four parts: an IF modulator and an IF-RF microwave converter. It also includes a high-power amplifier and a spectrum band limiter.

The IF modulator changes the input signals, and the converter adjusts them for satellite transmission. The HPA makes sure the signal is strong enough to reach the transponder.

Satellite Transponder

A transponder has input and output band-limiting devices, amplifiers, and a frequency converter.

The transponder acts as a repeater that works like a microwave repeater. Other transponder setups can also repeat signals.

The BPF input limits the total noise applied to the input of the LNA and is a tunnel diode. LNA’s output goes to a frequency converter, an oscillator, and a BPF. The BPF changes from a high frequency to a low frequency.

The TWT amplifier boosts the RF signal for better transmission to ground station receivers. SSP (solid-state amplifier) can also achieve a better consistency level than TWTs. Also, SSP devices can produce power at 50 watts at the greatest, while TWTs are 200 watts.

Drop Model

A ground station receiver has an input BPF, an LNA, and an RF to IF converter device, and the BPF works by limiting the power of the input noise to the LNA.

LNA, tunnel diode amplifier, or parametric amplifier, is a sensitive, low-noise device. The RF-to-IF converter acts as a combination scrambler filter that converts the RF signal into an IF frequency.

Orbital Satellites

Orbital satellites orbit the Earth in a low-altitude elliptical or circular pattern. When a satellite moves in the same direction as the Earth and faster, it’s a prograde orbit. If it moves in the opposite or same direction but slower, it’s a retrograde orbit.

Satellites orbit Earth and complete a whole spin every 15 minutes.

Orbital satellites have a downside. It takes a lot of work to set up ground stations. Additionally, the equipment needed is costly. Each ground station finds satellites in each orbit. Then, it connects its antennas to the satellite. The most significant advantage of these satellites is that they do not need propulsion engines. It keeps them in their orbits.

Other features of orbital satellites are the apogee and perigee. Apogee is the furthest distance from Earth reached by the orbital satellite. Perigee refers to the smallest space in the opposite direction. The sideline is the line in the center of the Earth that joins the perigee and the apogee.

Geostationary Satellites

Geostationary satellites move in a circle with the same speed as Earth and stay in one spot above a specific point on Earth.

The main advantage of these satellites is that they are accessible 100% of the time for all stations on Earth. A satellite’s shadow contains all stations with a visible path and is in the radiation pattern of satellite antennas.

The main disadvantage is that they must sophisticated and heavy propulsion devices to keep them stable in orbit. The orbital time of a geosynchronous satellite is the same 24 hours as that of Earth, and the typical parameters of a fixed orbit are orbits.

You can use Physics to determine the height and speed of a satellite in a fixed orbit. Suppose you want to know how long a geostationary satellite takes to rotate. In that case, it’s the same time as the Earth’s rotation.

We can figure out how long it takes for the Earth to rotate by using a faraway star instead of the sun. This star takes 23 hours, 56 minutes, and 4.1 seconds to complete a full rotation.

Force

There are three paths a satellite can take as it orbits the Earth.

1. Equatorial Orbit: The equatorial orbit is when the satellite circles above the equator.
2. Polar Orbit: A satellite is in a polar orbit when it circles over the north and south poles.
3. Inclined Orbit: When the installation moves in a different orbit, it’s called an inclined orbit.

Rising Node

An ascending node is where the orbit crosses the equatorial plane from south to north. A descending node refers to a point where the orbit crosses the equatorial plane from north to south.

We need to find a reference point to measure a satellite’s orbit. It can be a star, a point on Earth’s surface, or the center of its gravity. The node line goes through the center of the Earth and connects the ascending and descending nodes.

Longitude Lines

The location of the longitude lines extends from the north to the south pole. The meridian passing through Greenwich is the central meridian or longitude zero degrees. In total, it has 360 lines, equal to 18 complete circles.

Latitude lines are circles that run parallel to the equator. They help locate points on Earth’s surface when combined with longitude lines.

To aim an antenna at a satellite, you must calculate the angle and direction based on its height and position relative to the Earth’s surface.

Height Angle

The transmission will be enough if the elevation angle is too small. The wave’s distance in the atmosphere is shorter.

Azimuth

Azimuth is the horizontal pointing angle of an antenna. Start by facing north, then turn to the right until you face east. It will put you at an azimuth of 900.

You can get a south direction of 1800 and a west direction of 2700. The elevation and order may change. The location of the ground station and satellite determines this.

Satellite Classifications

There are two main classifications for communication satellite systems: spinners and three-axis stabilizers. Spinner satellites use the angular motion of their rotating bodies to provide rotation. Satellites that stabilize the process don’t move with the Earth’s surface.

Satellites in a fixed orbit share space and frequency in a specific location. Someone assigns them a particular longitude above the equator. The area used depends on the communication frequency band.

Satellites must space themselves out to avoid interference. The 6/4 and 14/12 GHz bands ease communication.

The higher the frequency of the carrier, the smaller the antenna diameter. Most domestic satellites use the 6/4 GHz band. It is also used for terrestrial microwave systems.

When making a satellite system, it’s essential to maintain existing microwave connections.