Circular – Understanding Network and Security for Far-Edge Computing

Sometimes, the antennas do not remain in a fixed orientation and rotate continually – sometimes at random. This is also known as the Faraday rotation. It is a common problem when communicating with satellites in space. Circular polarization is a method that can be used to overcome it:

Figure 3.5 – Circular polarization of a radio signal

This can be thought of as putting a spin on the signal as it leaves the transmitter. This makes the precise orientation of the receiving antenna less important but does increase the complexity of the antenna’s design.

Types of antennas

Several types of antennas can effectively handle circular polarization. Let’s take a look.

Helical

Helical antennas mimic the shape of the signal directly. Larger ones are obvious, but many are hidden beneath rubber or plastic covers:

Figure 3.6 – Examples of helical antennas designed for circular polarization

Microstrip

Also known as patch antennas 4, these consist of flat metal pieces of various sizes and shapes on a Printed Circuit Board (PCB). These can use either linear or circular polarization, depending on their design 5:

4 This is technically inaccurate, as a microstrip antenna consists of multiple patch antennas on the same PCB that work together as an array

5 Subtypes include the planar inverted-F antenna (PIFA) used in mobile devices

Figure 3.7 – A 2.4GHz patch antenna and an L-band SATCOM terminal

Advantages of this type include their low profile and small size. They are used in mobile phones, portable SATCOM terminals, Wi-Fi adapters in laptops, and similar applications where an external antenna is undesirable.

Parabolic

Most people associate parabolic antennas with satellite communications. However, parabolic dishes aren’t themselves the antenna. They are a method to increase the gain of a feed antenna by reflecting signals and focusing them onto it. This feed antenna can be polarized in any way, hence why there are parabolic antennas that have circular polarization and others that have linear polarization.