Antennas are considered one of the most important parts of wireless communication. An Antenna will transform the RF signal into an electromagnetic wave before it can be transmitted into free space.
During the time of transmission and reception, antennas must be present. Therefore, when there is radio wave communication, there should be antennas for transmitting and receiving.
Overview
When it comes to the communication system, the antenna used for transmission transforms the electrical signal into radio waves and transmits it to the receiver.
Once the radio waves are received by the receiver’s antenna, an equivalent electrical signal is produced and sent to the transmission line. Therefore, we can say that the antenna acts as the transitional element between the transmission line and free space.
In other words, antennas are considered transducers that transform RF electrical signals into electromagnetic waves with the same frequency. The electromagnetic waves released from the antenna will spread in free space quickly, just like the speed of light.
Why Are Antennas Essential?
We already know that antennas are essential for wireless communication systems. As the signal in free space spreads as an electromagnetic wave, it requires both transmitting and receiving ends. With an antenna, electromagnetic waves can be transmitted from one end to another using EMW without the need for a wired system. It serves as a transducer that can transform the RF signal into an EM wave on the transmitter side. Furthermore, the EM wave is transformed into an electrical signal on the receiver’s end.
This is made possible because antennas can produce both electric and magnetic fields based on the signals. When these two fields are combined, an electromagnetic wave is generated. Consequently, these two fields are perpendicular to each other.
In our daily lives, we regularly encounter wireless communication, including the signals we use to communicate with other people using the mobile network, the signals used by our television sets as we watch our favorite programs, and anything related to wireless communication. This means that antennas are essential in our day-to-day activities.
What are the Functions of Antennas?
Impedance Matching Device
As an impedance-matching device, the antennas will be responsible for determining if both ends have a perfect match. The purpose of this is to ensure that the transmitted signal can be received successfully without extreme reflections.
Transducer
It also serves as a transducer since it is capable of converting one particular form of energy into another form. On the side of the transmission, an electrical signal will be converted into a radio wave, while on the side of the receiver, the radio waves will be transformed back into their electrical form. This demonstrates that the maximum amount of transmitted power is moved at the load.
Radiator and Sensor
Both antennas for transmitting and receiving will be used as radiators and sensors of the generated electromagnetic waves. As a radiator, the transmitting antenna will spread the electromagnetic wave in free space. On the other hand, as a sensor, the receiving antenna will feel the presence of an electromagnetic wave in the free space and gathers it.
Coupler
Another significant feature of antennas is their coupling capability. Antennas can be used as couplers between the free space and the device that produces the RF signal or the transmission lines and free space.
How Does Radiation in an Antenna Work?
Antennas are typically composed of different short conductors that are integrated together. When the transmitting antenna is stimulated with an RF electrical signal, the charges in the conductor start a balanced motion, generating oscillations within the antenna.
This constant motion of charges produces electric and magnetic fields. This is similar to the nature of moving charges in an electric current where charges generate a back-and-forth motion, resulting in the production of electric and magnetic fields that produce electromagnetic radiation in the form of radio waves.
These disturbances from the antenna are scattered into free space, and the electromagnetic radiation spreads at the speed of light and is collected by the receiving antenna at the other end.
Once the electromagnetic wave reaches the receiving antenna, it generates movement in the charges present in the conductor, which produces a current within the conductor. The RF signal transmitted to the transmitting antenna is then transferred to the guided media by the receiving antenna.
What are the Parameters of an Antenna?
The following are the important characteristics of an antenna:
Radiation Pattern
For any efficient antenna, radiating a more balanced amount of energy in different directions might not be possible. This is because an antenna particularly radiates maximum energy in one direction and minimal only in the remaining directions. Thus, the measurement used is field strength. The field strength will indicate the generated radiation at a certain point at a specific distance from the antenna.
So, it can be computed based on the ratio of voltages between the two certain points on electric lines of force as well as the span of separation between these two certain points. Therefore, its unit is known as the volt per meter. This radiation pattern is very significant since it can help in recognizing the radiated energy found in space.
Radiation Intensity
Compared to the radiation pattern, the radiation intensity is not dependent on the distance between the transmitting and receiving antenna. Radiation intensity indicates the power per unit of a certain angle. Hence, the unit used is watts/ steradian or it can also be written as W/ sr.
Directivity
Antennas are considered naturally isotropic since they are capable of radiating energy in an omnidirectional way, which means that energy is equally distributed in different directions.
But basically, isotropic antennas do not have any existence. In theory, the energy radiated by the isotropic antenna is spread equally in different directions. The accomplished gain of the antenna is determined based on the ratio of power density and the average power radiated by the antenna.
Input Impedance
One of the significant features of antennas is impedance matching. In order to guarantee that the maximum power is transferred from the antenna toward the transmission line, there should be a perfect match between the input of the antenna and the input of the guided media.
Power Gain and Radiation Efficiency
Since antennas are comprised of conductors that include finite conductivity, hence, there will always be certain losses that are also known as ohmic losses. Thus, its efficiency is expressed by the ratio of power generated by the antenna and the actual input power applied to the antenna.
When it comes to the losses related to the antenna. The total input power will be based on the sum of power loss and radiated power. So, the power gain will be represented by the power generated by the antenna in a particular direction to the input power of the antenna.
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