We all had a rabbit-ear television at our house in childhood. Those televisions contained two small antennas at the top, which are called dipole antenna. A dipole antenna belongs to the linear antenna category.
However, the working process of the dipole antenna is different from the other types of antennas. So, the applications are also different. To use this antenna in compatible electric fields, you need to learn about its application.
Read on to find out its structure, types, working process, radiation pattern, and applications.
What Is Dipole Antenna?
Another name for a dipole antenna is dipole aerial or doublet. It’s widely used as a telecommunication and radio frequency antenna. This antenna contains two identical conductive rods divided by an insulator.
A coaxial cable connects with each rod of the antenna at the middle end. RF voltage is applied between the two conductors of this antenna. Dipole antennas are mostly used with rabbit-ear television and as a driven element with other antennas.
Basics Of Dipole Antenna
The word dipole refers to two poles, which are basically the two conductive materials. Antenna current and voltage flowing through the conductive materials emit radio signals or electromagnetic waves.
An intermediate feeder is connected to the dipole antenna’s transmitter or receiver, which helps the power to transfer from one place to another.
This antenna is often used as a resonant antenna. A dipole antenna resonates at a specific frequency when the feed point is shortened.
When/Who Invented Dipole Antenna
In 1887, a brilliant German physicist and experimentalist, Heinrich Hertz, revealed the radio wave existence using a dipole antenna with capacitive end-loading.
He invented the dipole antenna in 1886, which was used as the main receiving and RF radiating element later. To prove the existence of radio waves, he followed the electromagnetic antenna theory of James Clerk Maxwell.
Types Of Dipole Antenna
Among all the types of dipole antennas, three types are widely used for applications, such as half-wave dipole, folded dipole, and short dipole. Here are the details about these antenna types:
- Half-Wave Dipole Antenna
This antenna is also known as Hertzian Dipole Antenna. The wavelength of the operating frequency is half of the basic dipole antenna wavelength. However, the operating frequency of this antenna is between 3 kHz to 300 GHz.
Electric half-wavelength antennas are cost-efficient and not heavy. It operates at VHF in an omnidirectional pattern and is widely used as TV and radio antennas.
- Folded Dipole Antenna
This antenna can be folded back, that’s why it’s called folded dipole antenna. Another half-wave conductor is connected in parallel to connect to the other end representing a DC short circuit. Hence, this antenna can offer wider bandwidth and higher feed antenna impedance.
- Short Dipole
The wavelength of this antenna is much shortened than a half-wave dipole antenna. Therefore, the feed impedance response of short dipole is low. Hence, this antenna is mostly used for increasing the feed impedance surface of other antennae with a wide bandwidth.
Structure Of Dipole Antenna
The dipole antenna design is pretty simple; two conductive dipole elements with a coaxial feeder in the middle and radiating elements on both sides. The length of the metallic wire is half the maximum wavelength.
The antenna section contains the conductive elements divided by the insulator and connected to the feeder.
Besides, the radiating length is determined by the multiple properties of this antenna, for instance, operating frequency, feed impedance, etc. For the dipole antenna parameters, the length of the dipole radiation is an essential parameter.
A dipole antenna can activate with any type of antenna as a transmitter or receiver. Here’s the structure of the dipole as a transmitter and receiver.
- Dipole Antenna Transmitter
This antenna produces radio waves in the transmitter section. The flow of the power and voltage of this antenna generates magnetic and electric waves. It’s an elementary element of the antenna built with the conductor.
Here the conductor includes electric power. The energy intensity will fluctuate with time and transform into the radio frequency wave that emits in space.
- Dipole Antenna Receiver
The EM wave creates a little voltage while flowing through the dipole antenna at the receiver. Hence, the dipole antenna plays the role of signal source for the receiver input power.
An antenna receiver performs the opposite action of the transmitter. It collects radio frequency radiation and converts it into currents.
Working Of Dipole Antenna
It works by applying RF radiation in the antenna section center. Then the voltage and current flows within the conductive elements that transmit radio or electromagnetic waves signals outside.
While flowing, the current remains maximum and the voltage minimum in the middle. In contrast, the voltage is maximum and the current minimum in the antenna end. This process is called current distribution.
However, how the antenna will transmit current in space is determined by the radio pattern.
Radiation Of Dipole Antenna
The radiation pattern is vertical or omnidirectional to the antenna wire axis. At the antenna end, the radiation falls in the axis to zero. The antenna gain of the dipole is similar to the directive gain.
For a half-wave dipole, the maximum radiation gain is 2.15 dBi, while 1.76 dBi is for short dipoles. Generally, this antenna is used for receiving VHF terrestrial television bands.
The radio frequency of the dipole antenna is 54 to 88 MHz for band I and 174 to 216 MHz for band III and the wavelength is between 5.5 to 1.4m.
Advantages Of Dipole Antenna
Here are some advantages of dipole antenna:
- Balanced Antenna
The two-pole structure receives waves from different frequencies. Hence, it can receive balanced signals without losing reception quality.
- Variety Of Designs
Besides the basic television antenna, there are other designs like folded, short, or vertical antennae.
- Multiple Installing Direction
You can install a dipole antenna in multiple configurations like drooping, inverted V, sloping, etc. This is why it can also receive signals from any direction.
Disadvantages Of Dipole Antenna
The disadvantages of a dipole antenna are as follows:
- Antenna Size
Compared to the indoor dipole, the outdoor dipoles are pretty large and difficult to manage. Not only that, the outdoor antenna size makes it challenging to transport as well.
Applications Of Dipole Antenna
The application of this antenna are as follows:
- Used as a fundamental part with complicated antennas to form radiating elements.
- Can be utilized for both vertical and horizontal polarization.
- Applicable in telecommunication, television, and radio.
- Used for both receiving and transmitting antennas.
- VHF and UHF dipole antennas are used for mobile communication.
- Parabolic reflector dipole is used for satellite communication and radio astronomy.
- A folded dipole antenna is widely used for global TV reception.
- Used as an FM broadcast-receiving antenna, particularly broadcasting bands between 88 MHz to 108 MHz.
What are the types of dipole antenna?
Types of dipole antennas are Folded, Half-Wavelength, Short, FM, Vertical, and Fan dipole antenna.
What is the frequency range of the dipole antenna?
A dipole antenna contains a gain ability of more than 20 MHz to 2.2 GHz frequency range.
Why is it called a dipole antenna?
The word dipole stands for two poles. This antenna is built with two conductors, which are the two poles of the antenna; hence, it’s called a dipole antenna.
So you just learn the definition, working process, structure, types, benefits, and application of a dipole antenna. This antenna can generate a synthetic ground plane between the antenna elements. Due to the function of the dipole antenna, it’s mostly used in different fields and with other antennas.