Antennas are an essential component of a wireless communication system. Antennas are responsible for converting the RF signal into an electromagnetic wave.
Once it is converted, it will be transmitted into space. It is well-known that antennas are needed when transmitting and receiving. This means that transmitting and receiving antennas are both needed by radio wave communication.
How Do Antennas Work?
Generally, in a communication system, the function of the transmitting antenna is to transform an electrical signal into radio waves, then deliver it to the receiver.
Meanwhile, it will be the job of the receiving antenna to accept the radio waves, then create its equivalent electrical signal. Furthermore, this electrical signal will then be forwarded to the transmission line.
Hence, it plays the role of a transitional component between the transmission line and free space. Simply put, we can say that antennas are transducers that convert RF electrical signals into electromagnetic waves with the same frequency.
Also, the electromagnetic wave released from antennas reproduces in free space along with the speed of light.
Why Do We Need Antennas?
Antennas play a crucial role as the fundamental building block of wireless communication systems. They enable the conversion and propagation of signals as electronic waves in free space, eliminating the need for a wired connection.
Acting as transducers, antennas reproduce electromagnetic waves, transmitting them from one point to another. At the transmission end, the RF signal is transformed into an electromagnetic (EM) wave, while at the receiving end, the EM wave is converted back into an electrical signal.
Antennas generate electric and magnetic fields in accordance with the transmitted signal, combining them to produce an electromagnetic wave. We encounter wireless communication in various aspects of our daily lives, such as mobile network communication and receiving television signals.
All of these rely on antennas to facilitate wireless transmission. At the transmission end, electrical signals are converted into radio waves, while at the receiver’s end, these radio waves are transformed back into electrical signals.
Act As an Impedance Matching Device
It serves as an impedance-matching device since the antennas that are used at both ends are perfectly matched. The purpose of this is to guarantee that the transmitted signal can be fully received without any extreme reflections. This only indicates that the maximum amount of transmitted power is transported at the load.
Used As a Coupler
Another essential feature of antennas is their coupling capability. It serves as a coupler between the free space and transmission lines or between the device that produces the RF signal and the free space.
Used As a Sensor and Radiator
Both the transmission and receiving antennas serve as the radiators and sensors of electromagnetic waves. The transmission antenna will propagate electromagnetic waves in free space. On the other hand, the receiving antenna senses the existence of these electromagnetic waves in the free space and gathers them.
What Is the Mechanism of an Antenna?
Antennas are typically composed of short conductors that enable the transmission and reception of RF electrical signals. When the transmitting antenna is charged with an RF signal, the charges within the conductor begin to move in a balanced manner, resulting in oscillations within the antenna. These continuous charge movements generate electric and magnetic fields, which are inherent characteristics of moving charges.
As the electric current is transmitted through the conductor, the charges within the conductor oscillate back and forth, giving rise to the generation of electric and magnetic fields. These fields combine to produce electromagnetic radiation, specifically in the form of radio waves. The antenna disperses these disturbances into free space as electromagnetic radiation, propagating at the speed of light until they are received by the antenna at the other end.
When the electromagnetic waves reach the receiving antenna, they induce motion in the charges within its conductor, leading to the generation of electrical current within the conductor. Thus, the RF signal transmitted by the initial antenna is received by the receiving antenna and subsequently distributed to the guided media for further processing.
What Are the Parameters of Antenna?
The following are some of the characteristics of antennas:
Radiation Pattern
In practical antennas, achieving uniform energy radiation in all directions is not feasible. The antenna primarily radiates its maximum energy in a particular direction, while the energy radiated in other directions decreases. This radiation pattern is commonly measured in terms of field strength, which represents the amount of radiation received at a specific point located at a certain distance from the antenna.
The field strength can be measured by evaluating the voltage ratio between two endpoints on electric lines of force and the distance separating these endpoints. The unit used to express field strength is volts per meter (V/m). Understanding the radiation pattern is essential as it provides insight into how the antenna radiates energy in space and the directionality of its radiation.
Radiation Intensity
The radiation intensity is not dependent on the distance between the transmission and receiving antenna, which is contrary to the radiation pattern. The radiation intensity is provided as the power per unit solid angle. Therefore, the unit that will be used here is watts/ steradian and is represented as W/ sr.
Directivity
Generally, antennas are considered isotropic in nature if they tend to radiate the energy in Omni directional. This means that it is equal in different directions.
But commonly, isotropic antennas are not able to hold existence. In theory, if an isotropic antenna is used, then the energy released by it must be distributed equally in all directions. The antenna’s directive gain is measured by the ratio of power density to the average power released by the antenna.
Input Impedance
One of the most significant characteristics of an antenna is its impedance matching. To guarantee that the antenna transfers its maximum power to the transmission line, there should be a perfect match between the input of the antenna and the input of the guided media.
Radiation Effectiveness and Power Gain
Antennas consist of conductors that possess finite conductivity, resulting in associated losses known as ohmic losses. The radiation efficiency of an antenna is determined by the ratio of power radiated by the antenna to the actual input power supplied to the antenna.
The total input power to the antenna is the sum of radiated power and power losses. The power gain of an antenna is determined by the power radiated in a specific direction relative to the original input power provided to the antenna.
Bandwidth
The bandwidth of the antenna refers to the frequency range up to a point wherein the behavior of the antenna does not indicate any variation from a particular specified value.
Effective Length
The antenna’s effective length refers to the length of imaginary linear antennas that possess the same distribution of current with the same far-field in π/2 plane.
Effective Aperture
An effective aperture is also referred to as an effective area and it creates an association with the receiving antenna. It is defined as the capability to collect electromagnetic energy from free space.
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