How Antenna Works?
Antennas are frequently used in telecommunications, and we’ve already seen a variety of uses for them in this series of posts. Let’s get started learning about how an antenna works or How Antenna Works in this post.
Antennas receive electromagnetic waves and convert them to electric signals, or they receive electric signals and radiate them as electromagnetic waves. We’ll take a look at the science behind antennas in this piece. We’ve received a signal from the electric grid.
How do we convert it to an electromagnetic wave?
You might have a quick response in mind. That is, with a closed conductor, you may create a fluctuating magnetic field and an electric field surrounding it using the principle of electromagnetic induction. This shifting area around the source, on the other hand, is useless for sending signals. Instead of propagating, the electromagnetic field here simply fluctuates around the source.
The electromagnetic waves in an antenna must be isolated from the source and must propagate. Before we look at how an antenna is created, it’s important to understand the physics of wave separation.
Physics behind the Antenna
Consider two charges, one positive and another one is negative, separated by a distance. A dipole is a device that produces an electric field similar to the one displayed.
Assume that these charges are oscillating as depicted; the velocity at the midway of their journey will be highest, and the velocity at the ends of their trajectories will be zero. This velocity change causes the charged particles to accelerate and decelerate continuously. Now it’s up to you to figure it out.
How the electric field varies due to this movement?
Let’s focus on a single electric field line. After one-eighth of a time period, the wavefront formed at time zero extends and deforms as shown. This is unexpected. You would have expected a simple electric field like the one depicted here.
What caused the electric field to extend and form such a field?
This is due to the fact that the accelerating or decelerating charges generate an electric field with memory effects. The old electric field has a hard time adapting to the new situation. This memory effect of the electric field or kink creation of accelerating or decelerating charges requires some thought. In a later post, we’ll go through this fascinating issue in further depth.
If we continue our research in the same way, we can see that the wavefront ends meet at a single place after a quarter of a time period. Following that, the Wavefront is separated and propagated. Please keep in mind that this variable electric field will produce a varying magnetic field perpendicular to it. You can observe that the wave propagation is sinusoidal if you draw the electric field intensity fluctuation with distance. It’s worth noting that the wavelength of the propagation so produced is exactly double that of the dipole’s length. We’ll return to this topic later.
This is precisely what we require from an antenna. In other words, if we can arrange for the positive and negative charges to oscillate, we can build an antenna. In practice, creating such an oscillating charge is quite simple.
Apply a voltage signal to the center of a conducting rod with a bend in the middle. Assume you’ve applied a time-varying voltage signal as the signal. Consider the situation at the beginning of time. The electrons will be moved from the right of the dipole and aggregated on the left due to the influence of the voltage.
This means that the other end, which has lost electrons, gets positively charged automatically. This setup produced the same result as the preceding dipole charge situation, namely, positive and negative charges at the wire’s end. The positive and negative charges will shuttle back and forth as the voltage varies over time.
The simple dipole antenna exhibits the same behavior as the preceding section, resulting in wave propagation. We’ve seen how the antenna functions as a transmitter now. The transmitted signal’s frequency will be the same as the applied voltage signal’s frequency.
We can simply compute the wavelength of the propagation because it moves at the speed of light. The antenna length should be half the wavelength for perfect transmission.
ANTENNA AS A RECEIVER
The antenna’s functioning is reversible, and it can serve as a receiver if a propagating electromagnetic field strikes it. Let’s take a closer look at this phenomenon. Apply an electric field to the same antenna once more. The electrons will gather at one end of the rod at this point. An electric dipole is the same as this. The positive and negative charges collect at the opposite ends as the applied electric field changes.
At the antenna’s core, the varied charge accumulation results in a varying electric voltage signal. This voltage signal is created when the antenna is utilized as a receiver. The frequency of the output voltage signal matches that of the receiving electromagnetic wave.
The electric field arrangement shows that the antenna should be half the wavelength in size for perfect reception. We’ve seen that the antenna is an open circuit in all of these conversations.
Now let’s see a few practical antennas and how they work?
Dipole antennas were once utilized for TV reception. The colorful bar receives the signal and serves as a dipole. To focus the signal on the dipole, this antenna additionally requires a reflector and a director. A Yagi-Uda antenna is the name for the entire structure.
The received signal was transformed into electrical impulses by the dipole antenna, which was then transmitted to the television device via coaxial cable. Nowadays, we use dish television antennae. A parabolic-shaped reflector and a low-noise block downconverter are the two major components.
The LNBF receives electromagnetic signals from the satellite, which are focused via the parabolic dish. The parabolic’s shape is quite precise and well-designed.
As we observed in the basic dipole situation, voltage is induced at the probe. The resulting voltage signal is routed to a PCB for signal processing.
- Conversion from high to low frequency
These electrical impulses are delivered down to the television device through a coaxial cable after signal processing.
When you open an LNB, you’ll most likely find two probes rather than one. Perpendicular to the first probe is the second probe. Because of the two probe setup, the available spectrum can be exploited twice by transmitting waves with either horizontal or vertical polarisation. The horizontally polarised signal is detected by one probe, while the vertically polarised signal is detected by the other.
A patch antenna, like the one on your phone, is a whole different sort of antenna. A patch antenna is made up of a dielectric substance sandwiched between a metallic patch or strip and a ground plane. The metallic patch serves as a radiating element in this case. For proper transmission and reception, the length of the metal patch should be half the wavelength. Please show your support by clicking the support button, and thank you for reading this post. Our Upcoming post will be on a patch antenna.