Difference between antenna and satellite

How Antennas Receive and Transmit Signals

In communication systems, an antenna is an essential part since it transforms electrical impulses into electromagnetic waves and vice versa. It consists of an electrical conductor with alternating current flowing through it to produce electromagnetic fields that radiate radio waves into space beyond the conductor.

Functions of Antennas

They function on the principle of radiation. As such, when transmitting, the antennas accept input electrical signals from a transmitter and convert them into electromagnetic wave before emit it to the environment. During reception, these antennas take up returning electromagnetic waves, convert them back into electrical signals, and transfer them to the receiver. Therefore, they play a dual role that makes them a critical element in wireless communication.

The efficiency level varies considerably, depending on the design and material of antennas. For instance, an ordinary dipole antenna carries an efficiency level of approximately 80%. Hence, only 80% of the electrical power input is radiated out as an electromagnetic wave. On the other hand, high-performance elements like those used in broadcasting can reach up to 95%.

Transmission Power and Signal Range

Transmission power determines the range an antenna can cover. High power levels produce a stronger signal that covers an extensive range. Hence, a local FM transmitting power ion level of about 100,000 watts can reach areas within 100 kilometers of the station . However, cell phone antenna transmission levels are lower and ranged at about 20 watts, which only covers a few kilometers.

Material and Design

Copper and aluminum are the common materials used in antenna due to their high level of conductivity, weight, and cost factors . Some elements are uniquely designed to serve specific purposes and resonate at a fixed frequency. Their size is also engineered to fit the medium being transmitted. For example, satellite dish antennas are parabolic in shape, and the satellite dish is usually larger, measuring 2 to 3 meters in diameter . Their specific design helps in focusing weak and scarce signals from the satellite into a more massive area for higher quality reception.

The lifespan also varies, as outdoor antennas have to contend with harsher weather conditions. As such, the durability range is limited to between 10 and 15 years on average. The cost of any antenna is dependent on its size, complexity of design, and the material used in its manufacture. Indoor antennas used for the TV cost as low as K90 while large antennas for satellite circuits can cost as much as K1500 to over K3,000. The speed at which antennas emit signals when transmitting is almost at the speed of light, which is 300,000 kilometers per second. Hence, any message communicated through this medium is within the same timeframe for vast distances. A TV master can be hundreds of kilometers away, but a TV set will access the signal from the antenna almost immediately, often within microseconds.

How Satellites Receive and Transmit Signals

Satellites are signal receivers in space and at the same time transmitters of signals into space. They are used to create global communication systems, data transfer systems, and navigation systems. Satellites have a custom transmitter and receiver called a transponder that consists of a gain antenna, a low-noise input amplifier, a frequency converter, and a power amplifier . Major components of satellite transponders are the same. Notably, transponders are used to receive signals from earth stations, amplify the received signals, convert their frequency, and transmit them back to the earth. Any signal passing through a transponder is in the microwave band of the electromagnetic spectrum. The signal from the earth’s ground station is transmitted to the satellite through uplink signal or forward link. The transponder is also responsible for the transponding process, in which an uplink signal is rerouted to one of the downlink beams of the satellite.

The received signal from the earth is weak and has a low power output, which is the signal level required by the satellite to amplify it for its task. The receiver power output is a critical parameter that ultimately determines the efficiency of any communication system . Satellites use transponders whose power output ranges from a few to 500 watts, depending on the type of service they offer. Modern communication satellites operate one or more transponders to serve a wide range of customer needs.

The satellite’s signal range on earth depends on its output and the satellite transponders used. Geostationary satellites have an orbit of 35,786 kilometers above the surface of the earth, which covers a third of earth’s surface area. As such, they can serve the entire area of broadcast or communication station. On the other hand, communication efficiency is associated with the satellite’s ability to handle signals with minimum attenuation. The introduction of digital signal processing compensates for the use of signals within the available antenna power and transmission range. For efficient use of available power, the accepted signal quality level may differ in different satellites. Modulation several advanced systems like 256-QAM changes the effective throughput and data rate of communication lines. Additionally, satellites are constructed to be durable and robust to withstand harsh space conditions . The life span may not be the same for all satellites, with many such as communications satellites having life spans of up to 5 to 15 years. The construction and launch of a satellite are costly. 

Conclusion

Satellites are built to withstand harsh space conditions. They consist of a transponder, which is an integrated receiver and transmitter. Major components of the satellite transponders are the same. The tool is used to amplify weak received earth signals, transmit the back earth signals, and change them in frequency. The satellites’ communication range on earth depends on the satellite output and the transponder used. Advances in satellite technology include the increased life span, addition of more transponders, and efficient signal handling.