Thursday, 17 December 2020

Antennas engineering


In antennas engineering, antennas are one of the most important components of communication as they are used in the transmitter and receiver to transmit and receive electromagnetic signals.


The antennas are a metallic object, often of copper or aluminum, where the antennas convert the electrical signals passing through them into electromagnetic signals that spread in the air at a speed equal to the speed of light to transmit the signals to their receiving areas.


Types of antennas

The antennas have many types, the most important of which are:


1. Bipolar

It is two wires of a straight metal material, each end of which is fed by a double cable, and it is one of the most common types, and the length of each wire must be equal to a quarter of the wavelength, i.e. the length of the two wires must be equal to half the length of the wave.


2. The locked antenna

It is the same type as the previous antenna, except that we connected the two wires to each other and made them locked, as this led to an increase in the current passing through the antenna to double, which led to an increase in the transmission and reception power, which leads to an increase in the range of the transmission or reception, and is often used in the television antenna and some other uses.


3. Unipolar

It is completely an antenna like dual-polarity, except that we use only one wire instead of two wires, and this wire is equal to a quarter of the length of the wave and is widely used in wireless communication devices, and we see it above the buildings of relief, ambulance, firefighting, and police, because the ray coming from it is parallel to the surface of the earth, which leads to Covering the ground area at a certain distance, so it is used in police cars and wireless devices, as well as in radio and television transmission.


4. Yaji

It is widely used in television, where it is placed with the dipole or the voltage dipole, several other wires called inverters, and routers. If the length of the wire is greater than the dipole, it is called a reflector, and if it is shorter, it is called a wave, where the inverter reflects the signal on the diebol and the router focuses the signal on the diebol in order to improve the transmission and reception efficiency.


5. Annular antenna

It is a loop of wire used in transmitting and receiving, it has a relatively short range than other antennas, and it is placed inside the transmitter or receiver.


6. Helical antenna

It is a wire wrapped in a spiral way. The advantages of this antenna are its ability to transmit and receive a large range of frequencies without changing its length, such as diepol, and therefore it is widely used in communications of a large range of frequencies.


7. Antenna horn

It is a trumpet-shaped body made of a metal material and inside it is placed a receiving element such as monopoly or diepole, where the trumpet concentrates the signal and re-transmits it to a greater extent and is used in high frequencies and has several uses, especially in communications that take place over the seas.


8. Stratified antenna

It is often used in satellite communications, in very high-frequency communications, and in space communications, and it is a metal dish that reflects the signal and collects it at its focus where the transmitter or receiver is located, and we see it a lot in the satellite receivers where it is placed on top of the rooftops.


9. Strip antenna

It is a small strip of conductive material that is placed on the electronic panels of electronic devices due to its small size and lightweight. It is used in modern mobal devices and in airplanes where it is placed on the fuselage of the aircraft and in satellites and spacecraft.



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