Unlocking wireless communication: The magic of antennas

Antennas work as the eyes and ears of communication systems. It is a device that helps electromagnetic energy travel between an electronic device and the air. Thus, antennas act like a bridge connecting the electronic circuitry to the airwaves. Such a connection allows the device to transmit and receive signals. Antennas are present in many devices used in daily life, like phones and Wi-Fi. Different antennas are available for various purposes.

This guide covered topics as below:

• Types of antenna
  • Dipole antennas
  • Loop antennas
  • Horn antennas
  • Parabolic dish antennas
  • Yagi-Uda antennas
  • Patch antennas
  • Helical antennas

  • Whip antennas

• Single band and dual band antennas
• Key difference in single band and dual band antennas
• Performance characteristics of single-band and dual-band antenna
• Applications of single and dual band antenna
• Factors affecting the performance of single and dual-band antenna
• Cost of antennas

Dipole antennas

A dipole antenna is used for radio and television broadcasting. It is a kind of RF antenna. This antenna has two conductive elements in the form of rods or wires. The length of these conductive elements is half of the highest wavelength approximately in free space at the operation of frequency. An insulator material separates the two conductive materials at the center of the antenna. The following diagram shows a dipole antenna. This kind of antenna can be either horizontal or vertical.

Figure 1: Dipole antenna

The RF voltage source is present in the middle of the antenna. The two conductive elements supply voltage and current. These elements generate an electromagnetic or radio signal which radiates outside the antenna. The center of the antenna has the minimum voltage and maximum current. On the other hand, the current is minimum, and the voltage is maximum at the two ends of the dipole antenna. This is how the dipole antenna distributes the current.

Figure 2 depicts a dipole antenna pattern diagram that is vertical to the axis of the antenna. The radiation properties of the antenna are graphically depicted through the radiation pattern. This pattern describes how the antenna emits energy into space.

Figure 2: Radiation pattern

This antenna thus converts the electrical signals to RF electromagnetic signals. These signals are emitted at the transmitting end, changing the RF electromagnetic signals into electrical ones at the receiving side.

Loop antennas

This type of antenna is formed by bending a coil or uniform wire in the form of a loop. Simply put, the RF current-carrying coil is bent to shapes such as circles, squares, rectangles, ellipses, etc.

These antennas are simple, inexpensive, and versatile. They have many applications and are generally used for AM radio and low-frequency applications.

Figure 3: Loop antennas

The circular loop antenna type is the most widely used of all shapes. This is because the circular loop antennas provide simplicity in construction and analysis.

Loop antennas are also known as radiating coils, with any cross-section having single or multiple turns. A loop antenna with two or more turns is called a frame. The operating frequency allowed by a loop antenna ranges between 300 MHZ to 3 GHz.

Horn antennas

A horn antenna is a kind of aperture antenna. It is specially designed for microwave frequencies (300 MHz – 30 GHz). The end of the antenna is in a horn shape. Such a shape offers larger directivity, so the emitted signal can be easily transmitted to long distances.

Figure 4: Horn antenna

Parabolic dish antennas

Parabolic antennas collect or project energy, such as electromagnetic waves. This antenna is frequently used among all installed antennas in radar engineering.

Figure 5: Parabolic antenna

The circular parabolic reflector is made of metal. The construction is usually a frame with its inner side covered by a metal mesh. The width of the slots of the metal mesh must be less than λ/10. This metal covering is the reflector and acts as a mirror for the radar energy.

The circular parabolic dish antenna produces a pencil beam. If the reflector is elliptical, it will create a fan beam. Surveillance radars use two different curvatures in the horizontal and vertical planes to achieve the needed pencil beam in azimuth and the classical cosecant squared fan beam in elevation.

Parabolic dish antennas are highly directional and are commonly used for radio astronomy and satellite communications.

Yagi-Uda antennas

Yagi-Uda antenna (aka Yagi antenna) is a directional antenna with two or more parallel resonant antenna components acting as half-wave dipoles. This antenna comprises three parts: reflector, driven element, and directors. The single-driven component connects with the transmitter or receiver via a transmission line or other parasitic components. In most cases, the reflector and a number of directors (longer element) are parasitic elements.

Figure 6: Yagi-Uda antenna

These parasitic elements (shorter elements) act as passive resonators. They work with the driven element and are electrically disconnected from the transmitter or receiver. Yagi antennas generally function in the HF and UHF ranges, providing an operating frequency between 30 MegaHertz to 3 GigaHertz, even in minimal bandwidth. The unique design of these antennas allows good gain values (more than 10dB).

Yagi-Uda antennas are highly directional. They are commonly used for television reception and radio communication.

Patch antennas

A patch antenna is an antenna that is made by etching out a patch of conductive material on a dielectric surface. The dielectric material is mounted on a ground plane, where the ground plane supports the whole structure. The feed lines connected to the patch provide excitation to the antenna. Patch antennas are also known as microstrip or printed antennas, as the microstrip technique fabricates a printed circuit board.

Figure 7: Patch antenna

Patch antennas are commonly used for Wi-Fi and wireless communication.

Helical antennas

Helical antennas are the simplest ones used widely in ultra-high frequencies and work in the VHF and UHF ranges. These antennas have a conducting wire in a helix shape.

Figure 8: Helical antenna

Helical antennas have unique characteristics like wide bandwidth, high gain, and circular polarization. With a frequency range of 30MHz -3GHz, this antenna is used in space communication, satellite communications, and wireless networking.

Whip antennas

A whip antenna is a common example of a monopole radio antenna. This means that one antenna is replaced instead of two antennae working side-by-side or forming a loop. These antennas are popularly used in devices such as cell phones and hand-held radios.

The length of the whip decides its potential wavelength. A loading coil can be used anywhere along the length of the antenna to shorten the whip length. The inductance can thus be increased without increasing the whip size. The most common whips are half-wave and quarter-wave whips.

A whip antenna is vertically polarised as it is vertically mounted onto its base vehicle. Whips are often called omnidirectional because they radiate in every direction on a horizontal plane. However, it is not strictly true, as all whip antennas have an overhead conical blind spot.

Single band and dual band antennas

Antennas can be divided into single and dual bands depending on whether they can operate at single or multiple frequency bands.

A single-band antenna operates at a particular frequency. This operation is generally within a narrow range. Applications that require only one frequency band use these antennas. Traditional television systems and broadcast audio use single-band antennas. This type of antenna can be revised for a particular frequency for maximum efficiency and gain. Whip antennas, monopole antennas, loop antennas, Horn antennas, and helical antennas are examples of single-band antennas.

On the other hand, dual-band antennas operate at two different frequencies. These antennas have separate elements or feeding points for each frequency band. Dual-band antennas are commonly used in applications requiring multiple frequency bands. Mobile communication systems use dual-band antennas. This type of antenna can operate on various frequency bands without separating antennas. Dipole, patch, Yagi, and log-periodic antennas are examples of dual-band antennas.

Key difference in single band and dual band antennas

The difference between Single band antennas and dual-band antennas lies in their design. The difference lies in the number of their respective operational frequency bands.

Some key differences in the design of these two types of antennas:

Single-band antennas are designed to vibrate at a specific frequency. The physical dimensions of the antenna define this vibration. The length of the antenna fixes the operating frequency. These antennas have a narrow bandwidth and can only function at resonant and nearby frequencies.

Dual-band antennas are designed to have two distinct resonant frequencies. These frequencies are commonly used for two different frequency bands. Dual-band antennas are equipped with separate elements or feeding points for each frequency band, enabling them to operate at two distinct frequencies. The performance can be optimized for each frequency range if different physical dimensions are used to design each frequency band's antenna elements.

Performance characteristics of single-band and dual-band antenna

Regarding performance, single-band, and dual-band antennas have distinct advantages and disadvantages. These advantages depend upon the application. The following table compares the performance:

Applications of single and dual band antenna

Frequency requirements are key when choosing whether to use single-band or dual-band antennas. The following are some examples of where each type of antenna is typically used:

Single band antennas

• Cell phone towers
• GPS systems
• Satellite communication
• Radar systems
• Radio and television broadcasting

Dual band antennas

• Wi-Fi routers
• RFID systems
• Bluetooth devices
• Wireless access points
• Mobile phones

Factors affecting the performance of single and dual-band antenna

The location of single-band and dual-band antennas depends upon various factors. A good place assures better performance. These factors are:

1. Location: The antenna and the target must share an uninterrupted line of sight. There should be no interfering building structures or hostile environmental conditions.
2. Orientation: The orientation of the antenna is crucial. Directional antennas are more sensitive to orientation mistakes. For strong signal strength, the antenna must point to the target. However, antennas, such as omnidirectional antennas, lack specific orientation requirements.
3. Interference: The performance of single-band and dual-band antennas can degrade due to interference from different sources. The location chosen should be safe from interference as much as possible. Filters or shielding can be used to reduce interference.
4. Cable loss: The cables that bridge the antenna to the communication system can cause signal loss. High-quality cables help to maximize signal strength.

Cost of antennas (single band and dual band)

The cost of single-band and dual-band antennas can differ due to many factors. Several factors influence antenna costs:

Constituent materials

• Different materials can make up an antenna. These materials may significantly impact the cost. For example, using high-quality materials such as copper or aluminum can be more expensive than steel antennas.
• The availability and location of the materials used to make the antenna can also influence their price.

Size

• The size of the antenna can also affect the cost. Larger antennas are usually more costly than smaller antennas due to the increased material and manufacturing costs.
• However, the antenna size also depends on the frequency of operation. Higher frequencies usually require smaller antennas.

Level of performance

• Antennas optimized for higher performance can be costlier than antennas with lower performance. For example, antennas with wider bandwidth or superior efficiency are higher priced than antennas with lower performance.

Single band antennas

• Single-band antennas are generally cheaper than dual-band antennas. This is because these antennas are optimized for a single frequency band.
• The cost of a single-band antenna depends on the frequency band it is optimized for, the size of the antenna, and how it performs.

Dual-band antennas

• Dual-band antennas are generally priced higher than single-band antennas due to their ability to operate on two different frequency bands.
• Various factors, including the optimized frequency band, size, and performance, determine the cost of a dual-band antenna.

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