Monopole Antenna: Design, Working, and Types

The antenna was invented many years back for radio and TV broadcasts and communication. Monopole Antenna is a kind of radio antenna that contains a straight rod-shaped conductor mounted above a ground plane. It includes a single wire that transmits and receives signals in numerous wireless communication systems.

What is Monopole Antenna?

Monopole Antenna was discovered in the year 1895 and radio expert Guglielmo Marconi. This antenna's patent came in 1896 after this expert tried many experiments with the monopole antenna. It is widely used in mobile communications as well as internet networks.

This antenna is affordable and easy to build as well as install. It can be used in automobiles and portable FM radios.

Monopole Antenna Design

The size of a HF broadband conical monopole antenna is half the size of a dipole antenna. It is mounted on different types of ground planes with lengths shown as L. The directivity of a monopole antenna is connected to the dipole antenna. If the directivity of a dipole antenna with length 2L has a directivity of D1 (decibels), then the directivity of a monopole antenna with length L has a directivity of D1+3 (decibels).

No radiation has occurred below the ground plane and a monopole antenna is twice as a directive. The older mobile phones include monopole antennas.  

Types of Monopole Antenna

After discussing the design of the monopole antenna, we will further discuss the kinds of monopole antennas with features.

• Whip Antenna

The whip antenna is more flexible than other kinds of monopole antennae. It does not damage or crack easily with use or force. The antenna gets its name from the whip-like motion that exhibits when disturbed. A whip antenna contains a straight flexible rod or wire. The bottom portion of a whip antenna is connected to the receiver or radio transmitter.

This antenna is widely used in portable radios and designed with the help of interlocking telescoping metal tubes. The long whip antenna is used to mount on the vehicles.

• Helical Antenna

A helical antenna contains one or more conducting wires wounded in a helix form. When the helical antenna includes one helical wire, this kind of antenna is called a monofilar. On the other hand, the helical antenna with minimum of 4 wires in a helix is called bifilar.

• Random Wire Antenna

A random wire antenna contains a long wire that is suspended over the ground where the wire is straight or stuck in between the objects. The efficiency of a random wire antenna changes from one fix to another.

This type of antenna is used as receiving antennas on medium wave and long wave bands. It is also used as a transmitting antenna on different bands for emergency or outdoor places where there is no need to mount permanent antennas.

• Rubber Ducky Antenna

A rubber ducky antenna is a kind of short monopole antenna that works like a base-loaded whip antenna. It contains a narrow helix-shaped springy wire closed within a rubber jacket or plastic to guard the antenna. A rubber ducky antenna is widely used in radio equipment at VHF and UHF frequencies.

In addition, the antenna is used in many portable radio devices like scanners portable transceivers, and walkie-talkies. It is the right type of antenna for handheld operations.

• Mast Radiator

Mast Radiator is a kind of monopole antenna. It is a radiating tower where the metal structure is energized and works like an antenna. Mast Radiator is generally used to transmit antennas that work at low frequencies within LF and MF bands. It is mainly used for AM broadcasting stations. Moreover, the base of this antenna is mounted on a nonconductive support to safeguard it from the ground. 

• Umbrella Antenna

Umbrella is a type of wire monopole antenna that is used as a transmitting antenna in different bands such as MF, LF, and VLF. It works at low frequencies which makes it impractical to make a complete-size quarter-wave monopole antenna. The external end of the radial wire slopes down from the antenna’s pinnacle and is connected to a supporting rope via an insulator attached to the earth. Radial wires make this antenna the giant umbrella with a wire frame.

• T-Antenna

T-Antenna is a kind of monopole radio antenna. It is also called a T-aerial antenna or flat-top antenna. It contains one or more horizontal wires that are balanced between 2 radio masts. The horizontal wire is connected to the middle of the horizontal wires and hangs down close to the ground.

These antennas are generally used in various bands such as VLF, LF, and MF. They are also used as transmitting antennas in medium wave and long wave AM broadcasting stations and amateur radio stations. In the case of shortwave listening, T-antennas are used as receiving antennae.  

• Folded Unipole Antenna

Folded Unipole antenna is a type of monopole mast radiator antenna used as a transmitting antenna for AM radio broadcasting stations. It mainly includes a vertical or mast metal rod connected to its grounding system that contains buried wires. The mast is covered by vertical wires which are electrically connected at the mast’s pinnacle. The wires are connected by a metal ring close to the base of the mast and the feeding power of the feed line from the transmitter is attached to the ground. It is mainly used when an AM radio station shares a tower with other antennas.

Advantages of Monopole Antenna

Now, we will discuss the benefits of a monopole antenna. Some of the major benefits of a monopole antenna are:

• A monopole antenna is easy to build with limited materials. It can be easily installed anywhere without professional equipment or tools.
• This antenna is affordable to build and has a sturdy construction.
• It has a fairly high reactive impedance in the high-frequency range.
• A vertical monopole antenna is used for the frequency that is shorter than 2/3^rd of the wavelength.
• The efficiency of a monopole antenna gets better when the antenna becomes longer and the ground losses are reduced.
• A printed monopole antenna is used in many areas because of various benefits. Some of the major benefits of using a printed monopole antenna include simple fabrication, cheap cost, less weight, low profile, and combination with other devices.
• A Monopole antenna is a kind of omnidirectional antenna that uses less space.
• This antenna can handle communications within any path except vertically on the top of any antenna.

Disadvantages of Monopole Antenna

A monopole antenna has several disadvantages such as:

• Monopole antenna has poor radiation within all directions. It radiates evenly in all directions.
• These are expensive monopole antennas.
• Signal reflections are caused by metal objects and the ground. This antenna gives both horizontally and vertically polarized signals.
• Size and design constraints that are needed for the ground plane are restrictive in this antenna.
• The radiation pattern of a monopole antenna depends on the direction of the ground plane.

Where is a Monopole Antenna Used?

A monopole antenna is used in many applications such as:

• This antenna is widely used in different fields such as radar technology, space science, and research. It is also used in many biomedical applications.
• It is used as a resonant antenna in which the rod of the antenna works like an open resonator and fluctuates through standing waves of voltage through the length. The length of this antenna is determined by the radio waves' wavelength.
• A monopole antenna is used in many wireless communication systems.
• The antenna with a low-profile pentagonal model is used for wearable applications.
• A monopole antenna is used in many portable AM or FM radios and automobiles.
• An efficient and affordable monopole antenna is used in many multi-band and dual-band applications.

Conclusion

A monopole antenna is used for many years in several wireless devices like mobile phones and FM radios. It is simple to build, and install and includes a solid construction. The characteristics of this antenna depend on radiator geometry and ground plane.

It has several benefits such as affordability, low profile, and easy working with other active devices.