Loop Antenna: Advantages and Disadvantages

This page covers the advantages and disadvantages of Loop Antennas. It details the benefits and drawbacks of Loop Antennas. It also provides a basic introduction to Loop Antennas.

What is a Loop Antenna?

Introduction: A loop antenna consists of one or more turns of wire, typically shaped in a circular or rectangular form, as illustrated in Figure 1.

The critical characteristic of a loop antenna is that its dimensions are significantly smaller than the wavelength of the signal it’s intended to receive or transmit. This ensures that the current flowing throughout the loop remains largely in phase.

The loop antenna generates a magnetic field (H) that surrounds it, oriented perpendicularly to the loop at every point.

The radiation pattern of a loop antenna closely resembles that of an elementary doublet, as shown in Figure 2. This means that minimal radiation is received perpendicular to the plane of the loop. This characteristic makes it useful for direction-finding applications.

Advantages of Loop Antennas

Here are the key benefits of using a Loop Antenna:

• Lightweight: They are relatively light in weight, making them easy to handle and mount.
• Simple and Compact: Loop antennas boast a simple and compact structure, contributing to their ease of use.
• Economical: They are generally inexpensive to manufacture and deploy.
• Portable Applications: Loop antennas are well-suited for portable applications, such as direction finding.
• Variety: They come in a variety of designs, including Adcock antennas, Alford loops, cloverleaf antennas, and Bellini-Tosi antennas.

Disadvantages of Loop Antennas

Here are the main drawbacks associated with Loop Antennas:

• Poor Efficiency (Small Loops): Small loops exhibit poor efficiency, making them primarily suitable as receiving antennas at lower frequencies.
• Low Radiation Resistance (Small Loops): Small loop antennas have a very low radiation resistance. This leads to power loss in the form of heat due to the flow of current at high levels. For this reason, larger loop antennas are often preferred.