Antennas are a critical component of any wireless communication system. They are used to transmit and receive radio frequency signals that carry information such as radio, television, mobile phone, WiFi, and satellite communications. Choosing the right antenna for an application requires understanding the different types available and their characteristics. In this guide, we will cover the following major types of antennas. Understanding these antenna types and their properties will allow you to select the right antenna for long-distance communication, directional transmission, broadcast coverage and other wireless applications. We will explore each in detail in the sections below.
1. Monopole Antenna
The monopole antenna is a simple yet effective antenna design consisting of a single conductive rod or wire mounted perpendicularly over some kind of conducting surface, most commonly a metal ground plane. Monopole antennas are typically omnidirectional, meaning they radiate power uniformly in all directions perpendicular to the antenna. They function as resonators, with the length of the monopole rod roughly equal to one quarter of the wavelength of the radio waves being transmitted/received. Overall, the monopole is an indispensable antenna design that finds use in a wide variety of radio systems due to its simplicity, cost-effectiveness, and adequate performance. It works very well for omnidirectional communications applications where directionality is not required.
2. Yagi Antenna
The Yagi antenna, also known as the Yagi-Uda antenna, is a directional antenna consisting of an array of parallel rod elements in front of a reflector. It was invented in 1926 by Shintaro Uda and Hidetsugu Yagi.
The Yagi antenna has three main components:
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Reflector – A single element, typically a rod or sheet, placed behind the active elements.
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Driven element – The active element that is connected directly to the transmission line. It is typically slightly longer than half the wavelength.
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Director elements – These are passive elements, typically rods, placed in front of the driven element. Directors are slightly shorter than half the wavelength.
The reflector reflects radio waves in the direction of the driven element. The driven element absorbs transmitted power and re-radiates it. The director elements focus the radio waves in the desired direction, increasing the antenna’s directionality and gain. Due to their high gain and directionality, Yagi antennas are ideal when long-distance communication is required between fixed points. By optimizing the element lengths and spacing, Yagi antennas can achieve high gain in a lightweight, compact directional antenna. But bandwidth and polarization limitations make them suitable only for specific fixed point applications.
3. Bowtie Antenna
The bowtie antenna, also known as the butterfly antenna, is a wideband dipole antenna shaped like a bow tie or butterfly. The bowtie antenna consists of two triangular metallic elements facing each other to form a bowtie shape. Unlike a regular dipole, the triangular elements act as wideband radiators. The two elements are separated by a small gap at the center. The antenna is fed using a coaxial cable attached across the gap. The flared shape gives the bowtie antenna a wide impedance bandwidth compared to a thin dipole antenna. Bowtie antennas are widely used as feed elements in parabolic dish antennas and radar systems that require wideband performance. They are suitable for various wireless applications including cellphone signal boosters, WiFi routers, radio communications, satellite communications, and medical applications. The bowtie’s flared shape allows it to operate over a wide frequency range. It offers good performance across wireless applications that need wide bandwidth in a simple omnidirectional antenna. However, the size can be a limitation in compact devices. Overall, the bowtie is a versatile antenna choice when a wideband dipole is required.
4. Dipole Antenna
The dipole antenna, also known as a doublet antenna, is a simple radio frequency antenna that is commonly used for wireless communications. Dipoles are the simplest and most widely used type of antenna. A dipole antenna consists of two identical conductive elements or poles that are magnetically and electrically symmetrical. The poles are aligned along the same axis and have equal lengths. Dipoles derive their name from their bi-polar construction with two poles. These two poles are directly connected to a power source, typically a transmission line or feeder cable that connects to the transmitter. A dipole antenna has omnidirectional radiation patterns when mounted vertically. It radiates equally well in all horizontal directions perpendicular to the axis of the poles. Dipoles have a doughnut-shaped radiation pattern that’s most intense across the equatorial region. They exhibit little to no radiation along the axis of the dipole. Dipole antennas are versatile and commonly used for many wireless applications across a wide range of RF bands. In summary, the ubiquitous dipole is one of the most basic yet effective antenna designs. Its omnidirectional radiation, simplicity, and low cost make it the antenna of choice for a wide range of wireless communications applications.
5. Loop Antenna
A loop antenna, also known as a loop aerial, is a radio antenna consisting of a loop or coil of wire, tubing, or other electrical conductor. Loop antennas can be designed in different shapes like circles, rectangles or triangles. The most common type is the small loop antenna or magnetic loop antenna used in the LF, MF and HF bands. Loop antennas useful where space is limited. The directivity provides good signal rejection capabilities. However, the narrow bandwidth and high Q factor limit applications. Overall, loop antennas provide good performance in a small form factor but lack wide bandwidth capabilities.
6. Dish Antenna
Dish antennas, also known as parabolic antennas, are directional antennas that are shaped like a dish or parabola. They work by focusing radio waves onto a specific point or receiver. Dish antennas are commonly used for satellite communications, radio telescopes, tracking spacecraft, and for receiving satellite television broadcasts. The curved dish shape allows the antenna to be pointed to focus on signals from a specific satellite or radio source. By focusing the radio waves into a concentrated beam, dish antennas can achieve very high gain and sensitivity, picking up faint signals from distant transmitters. Their directionality allows them to filter out unwanted interference or noise from other directions. However, this also means they must be accurately pointed and are only able to receive one signal at a time.
Antennas are a critical component of any radio communications system. They allow the transmission and reception of radio waves, enabling wireless communication. In this article, we covered some of the most common types of antennas used today. Antennas transform electric currents into radio waves and vice versa. Without them, technologies like broadcast radio, WiFi, cell phones, GPS, and radar would not be possible. Their ability to send and discriminate signals in particular directions enables wireless signals to be transmitted between specific locations without interfering with other equipment. Whether communicating across a room or across planetary distances, antennas enable the modern world of wireless connectivity.
