Horn antennas are largely used in both UHF and VHF frequencies. They run smoothly at a frequency above 300 MHz. Horn antenna is used as a feed horn in large antenna structures like parabolic antennas.
In this article, we will discuss a horn antenna, its design, working process, benefits, and disadvantages. This blog will also discuss various other things related to a horn antenna.
What is Horn Antenna?
Before we discuss everything related to high gain horn antenna, let us know what a horn antenna is. It is a type of antenna when the end of an antenna is tapered in the horn shape. These antennas normally operate in microwave frequency.
The antenna works in ultra-high frequencies starting from 300 MHz to 30 GHz. The first horn antenna was developed with pioneering experiments via microwaves in the year 1897 by Jagdish Chandra Bose.
The current horn antenna was discovered in the year 1938 by G.C. Southworth and Wilmer Barrow. The experts continued to find design and invent the radiation pattern of a horn antenna with its applications as well.
Horn antennas are also called microwave antennas as they are popular in microwave and waveguide transmission. Because of the flared-out structure of the antenna, the directivity is greater than usual and emitted signals travel far-off distances.
Meaning of waveguide
A waveguide is a hollow tube that lets the energy gets radiated in space when excited at one end and opened at the other end. The amount of energy radiated by the wavelength is more significant than the two-wire transmission line.
There is no central conductor in the waveguide, and it can be either cylindrical or rectangular. This antenna allows the propagation of electromagnetic waves from one end to another. Moreover, this antenna is considered a high-pass filter as it permits the propagation of high-frequency signals.
Horn Antenna Design
The horn antenna has a flared-out structure that forms like a horn. These antennas are used for receiving and transmitting RF microwave signals. Apart from that, the horn antennas are also used in a narrow beam with direct radio waves and waveguide feeds.
The flared part can be in shape such as rectangular, conical, or square. A minimum-sized antenna is necessary for smooth working. The antenna with a large wavelength and small horn size does not work properly.
In a horn antenna, the fraction of incident energy will radiate from the wavelength’s entry, and the remaining energy will reflect from the same entry as it has an open entry. The end is opened in an electromagnetic horn form to reduce the drawbacks of the waveguide. A smooth transition is allowed between the wavelength and space, giving better directivity toward the radio waves.
Changing the waveguide like a horn structure will eliminate 377 ohms impedance. This will lead to the emission of incident energy in the forwarding direction by reducing the diffraction on the edges. The transmitting antenna’s directivity will enhance with superior gain.
In the case of a horn antenna, the field will be generated when the wavelength’s one end is excited. Normally, the fields within the free space and waveguide transmit similarly.
Once the traversing field comes to the waveguide end, it transmits similarly to the free space. At the end of the wavelength, spherical wavefronts are attained.
Types of Horn Antennas
Horn antenna is mainly divided into three types namely pyramidal, conical, and exponential. Now, let us have a look at the different types of horn antennas in this section:
- Pyramidal horn
You will get some idea by reading the name of this antenna. This antenna has a shape like a pyramid via a rectangular cross-section. It is formed by flaring both waveguide walls.
In a pyramid horn, a rectangular waveguide is utilized and flaring is done within both the direction of magnetic and electric field vectors. A pyramidal horn antenna is used to radiate linearly polarized radio waves and is used with rectangular waveguides.
- Sectoral horn
A sectoral horn antenna is a kind of antenna in which only one pair of faces are flared whereas the other pair is parallel. This antenna produces a fan-shaped thin beam in the flared side’s plane and a broad in the narrow side’s plane. Sectoral horn antenna is used as feed horns for wide search radar antennas. It is divided into types namely E-plane and H-plane.
- Conical Horn Antenna
This antenna has the shape of a cone with a circular cross-section. It is widely used via cylindrical waveguides. Apart from that, the conical antenna formation is also an effect of a circular waveguide flaring. Moreover, the conical horn antennas can be either conical or biconical.
- Exponential Horn Antenna
Another name for an exponential horn antenna is a scalar horn antenna. This kind of antenna has an exponentially tapered face that develops a curved portion from the antenna opening to the waveguide termination.
In this antenna, the separating space between the sides increases exponentially as a function of the length. These antennas offer a constant impedance to a huge frequency and have fewer possibilities of internal reflections.
The exponential horn antenna’s design will decrease the number of internal reflections and allow a constant impedance and electrical performance over an extremely broad bandwidth.
- E-plane horn antenna
In the E-plane horn antenna, one waveguide wall of the antenna is flared with the electric field vector direction.
- H-plane horn antenna
The wavelength walls are flared with the magnetic field vector direction in an H-plane antenna.
Advantages of Horn Antenna
Horn antenna has various advantages such as:
- Construction of a horn antenna is very simple as it can be configured with the help of a waveguide.
- This antenna provides few reflections.
- Horn antenna offers good impedance matching.
- It is highly directional and provides higher directivity than other kinds of antennas.
- Lack of resonance element in the structure of a horn antenna allows it to operate on a wide bandwidth.
- In the case of a horn antenna, the small minor lobes are developed.
- This antenna has a low SWR or standing wave ratio.
- The performance of a horn antenna is stable for all frequency ranges.
- It has a simple design, and it is easy to connect to the waveguide and a coaxial feeder.
- Horn antenna is used as a feed horn for big parabolic antennas.
- It has no standing waves.
Disadvantages of Horn Antenna
With advantages, the horn antenna also has many disadvantages such as:
- Horn antenna’s directivity depends on the flare angle.
- This antenna radiates energy in a spherical wavefront shape and so this antenna does not offer a sharp beam or directive beam.
- These antennas have a limited gain such as 20 dB. You will need a larger opening of the horn to get the antenna gain. A larger opening will make the length of the horn larger.
- Flare dimensions must be large so that the antenna does not become bulky in size.
- The length of the flare and flare angle should not be very small.
Where is a horn antenna used?
After discussing the advantages and disadvantages of a horn antenna, we will discuss the applications of a horn antenna in the below section:
- Horn antenna is used in microwave-based applications.
- It is used for astronomical studies.
- These horn antennas are used in labs to measure various antenna parameters.
- Horn antenna can be used as a feed element.
- Parabolic reflectors are excited by feeding antennas like horn antennas. So, the higher directivity offered in this antenna allows it to light up the reflectors.
- Horn cameras are widely used in speed enforcement cameras to protect the photos from reflections that spoil the images.
- Horn dimensions should be high for high gain to use in moderate gain operations.
Read: Everything you need to Know about Horn Antenna
Final words
This is all about the working of a horn antenna, it’s working, its design, and its benefits and limitations. Horn antennas are normally used in microwave region that offers less VSWR, fairly wide bandwidth, and high gain. It is widely used in cameras and other devices where there are fewer reflections.
