Radio Frequency Identification systems use antennas to facilitate communication between the reader and the tags. There are separate classes of antennas available in the market, all with different features and specifications. In this blog, we will discuss Linear and Circular polarized antenna types. Their advantages, disadvantages, and applications in various industries.
Antennas are an essential part of an RFID system. They are responsible for broadcasting the interrogation signal from the reader and receiving the signals from the tags. There are different classifications of antennas based on factors like mobility, signal polarity, operational frequency, etc. Today, we will discuss antennas based on their polarization. Based on these criteria, radio frequency identification antenna can be of two types, namely – Linear, and Circular.
So, let’s have a brief discussion about the following types.
Linear Polarization Antenna
As the name suggests, these antennas broadcast the radio signals alone on a singular plane. Meaning the radio waves propagate along a single axis, either X or Y. These types of antennas are rather simple to produce and require less power input. There are both pros and cons of these antennas.
Circular Polarization Antenna
Unlike linear, a circular polarization antenna works by broadcasting the signal in a corkscrew pattern. The signals propagate in a helix pattern around the antenna's length as its axis. Like any piece of technology, this has its advantages and disadvantages. They are a bit more complex to manufacture and require more power input.
Benefits of Using a Linear Polarized Antenna
As noted above, these types of antennas have certain advantages to their application.
(A). Linear polarization antennas are very simple to make and require fewer manufacturing processes and materials. Unlike circular ones, which require two conductors patched at 45 degrees to achieve the desired effect.
(B). These also provide a higher gain/broadcast range due to a smaller broadcast angle, compared to a circular polarization antenna.
(C). Higher gain also means that a linear antenna requires less input power than a circular antenna, to propagate radio signals for the same distance.
(D). These are very target specific, meaning that they have a better reading focus, thus, reducing the chances of reading tags outside of the intended interrogation zone.
Advantages of Choosing a Circular Polarized Antenna
(A). Circular polarization antennas don’t need to be put along the same plane as the RFID tags, unlike linear antennas, which can only read tags if they are in the same plane.
(B). These antennas can work with multiple assembly lines, supply lines, etc at once.
(C). Circular antennas propagate signals at multiple angles, meaning that the signals reflected by any obstacle cannot interfere with the broadcasting signals. Unlike linear antennas, they face issues with reading tags in the presence of an obstacle in the line of sight.
(D). These antennas are also more resistant to signal degradation due to environmental disturbances like snow, rain, dust, etc.
Applications of Linear and Circular Polarized Antenna
A linear polarized antenna is usually applicable in scenarios where you want to only scan tags in a single direction/plane. For example, we use such antennas in RFID security gate panels, and ground mat antenna in private parking or warehouses. We also use them in display cabinets to provide asset tracking for valuable items.
In the case of circular polarized antenna, we use it in situations where we need to read along multiple angles. For example, these antennas are used in toll plazas, warehouse inventories, manufacturing/assembly lines, etc. Due to their resistance to signal degradation, they are used in industries where metal surfaces are prevalent.
Conclusion
As discussed above, there are stark differences between the functioning and applications of both linear & circular polarized antenna. For example, the range difference and the reading field-of-view between the two. Therefore, you need to keep certain factors in mind while considering the type of antenna you want to buy for your business.
If you haven’t yet, read the blog above to learn about choosing a linear or circular polarized antenna for your RFID setup.
Frequently Asked Questions
Q1. Which is better linear or circular polarization?
Ans - Both types of antennas have different applications, advantages, and disadvantages. There is no, better type of antenna. The answer depends on what application you want to use it for, and the nature of your business. Check out the blog above to learn more.
Q2. What is the difference between linear and circular polarized antennas?
Ans - The primary difference between the two types of radio frequency identification antennas is the manner in which the radio waves propagate from them. Linear antennas broadcast signals along a single plane, giving it better range and smaller focus points. A circular antenna, however, propagates signals along a helical axis/circular pattern around the antenna’s length. These have shorter ranges for the same power but are covered wide at a wide angle.
Q3. What are the disadvantages of linear polarization in antenna?
Ans - Linear antennas can only read tags that are in the same plane of origin as it is. They are also highly vulnerable to signal degradation in the presence of an obstacle in their line of sight. Similarly, they do not function well in rainy and dust-filled environments, due to signal reflection.
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