An antenna is the foundation of modern wireless communication. We use them everywhere, from our smartphones to large broadcasting facilities like News Studios. The job of an antenna is to convert electrical digital signals into electromagnetic radiation (radio waves) and broadcast them, ad receive them. Even in an RFID system, we need antennas to facilitate communication between the reader and the tags.
In an RF system, the antennas come separate from the readers, and you can connect multiple antennas to a reader. But how do you make sure that you are getting the best possible functionality out of your systems? Luckily, that is exactly what we will talk about today.
What are the Performance Specifications of RFID Antennas?
There are a lot of factors that affect the functioning limitations of an antenna. All of these are interconnected and have an effect not only on the functioning but also on each other. However, there are three primary specifications that affect an antenna’s performance:
(A). Gain
In terms of radio signals, gain refers to the power output of an antenna in its peak direction compared to the power output of an isotropic antenna of the same power input. An isotropic antenna is a hypothetical antenna that transmits signals equally in a perfect sphere. The SI unit of Gain is dBi, meaning Decibels per Isotropic Gain).
In practical applications, antennas usually transmit the majority of their power in a particular direction/area of effect. Keeping in mind the inverse square, i.e., the energy of an electromagnetic wave decreases by the square of the distance it has traveled. This happens because the signal expands over an area as it travels, decreasing its intensity.
Meaning, that between two antennas of the same input power, the antenna which can send signals father will have a smaller spread/cone area of the broadcast. This antenna will have a higher gain. In short, the higher the gain on an antenna, the lower will be its reading area.
(B). Polarization
The polarization refers to the directions & planes along which an antenna broadcasts a signal. There are two types of antenna polarization, namely – Linear Polarization, and Circular Polarization. A linear polarized antenna will broadcast signals along one axis. On the other hand, a circularly polarized antenna will broadcast signals along multiple axes, in a helical pattern.
As linear antenna broadcast on a single axis, their cone of spread is far smaller than a circular antenna. This also gives them a far longer range than a circular antenna, however, their biggest disadvantage is that they cannot communicate with tags that are in a different orientation than them.
(C). Orientation
Lastly, position the antenna in a way that the objects fall inside its peak broadcast zone. As discussed above, antennas have a particular zone, where the signal power is at its highest. This zone has the longest range and the best chance of clear communication.
How to Maximize the Performance of RFID Antennas?
There are a few factors that can hamper or negatively affect the functioning of a perfectly good antenna. These issues can be solved easily or at least accounted for, once you are aware of them. So, below are some issues and some habits to maximize the performance of your antennas.
(A). Remove Interference
Although radio signals are very good at transmitting information, they are not perfect. There are some things that can act as a source of severe interference for radio transmission. Things like metal objects, poorly insulated electric equipment or wiring, etc.
Due to the property of metals to absorb and reflect/backscatter radio waves, antennas can have a tough time broadcasting effectively in an environment with lots of metal objects. In the case of poorly insulated wirings and electronics, the magnetic field generated by the circuits in those can interfere with the radio signals from the antenna by inducing eddy currents.
(B). More than One Antenna
A great way to improve antenna performance in an area is to increase the number of antennas covering that area. There are several ways of integrating multiple antennas at one area/checkpoint. One way is to orient multiple antennas operating at the same frequency along different axes. Another method is to install antennas of different frequencies at a single area, to read different types of tags.
This method can boost the total power output of radio signals in the reading area, resulting in better-quality communication between the tags and the antennas.
(C). Environmental Elements
Aside from metal objects, there are some other things that can affect the propagation of radio signals. These things are water, dust, moisture, etc. Water being a conductive medium can severely affect the movement of radio signals through it. On the other hand, dust particles can become a cause of interference and block the signals.
Frequently Asked Questions
Q1. What is the best antenna for RFID?
There is no best antenna for RFID, the best choice of antenna for you depends on the application you are going to use it for. For example, linear polarized antennas have a better communication range, but they need the tags to be in the orientation and height of the antenna.
Q2. What is the best material for an RF antenna?
There are a couple of factors to consider while deciding on a material to build an antenna from, these are:
(A). Conductivity – The conductivity of a material shows how easily it can transmit electricity, meaning that loss of energy while converting the input energy to the broadcasted signals. A material with high conductivity will have minimal loss of power, and vice-versa.
(B). Corrosion Resistance – Antennas are used in a wide variety of environments, meaning that there is a good chance of them being exposed to the elements. Due to this, antennas need to be highly resistant to corrosion, so they can work effectively in all types of environments.
(C). Material Cost – The next thing to keep in mind is the cost of material in antenna. For example, silver is the best conductor of electricity, but it is also extremely expensive when compared to some alternatives.
Q3. What is the maximum efficiency of the antenna?
In theoretical terms, the maximum efficiency of an antenna can be 100% efficient. Meaning, that the difference between the input power to the antenna is equal to the output power of the radio signal it broadcasts. However, in practical applications, factors like environmental factors, resistance, etc., stop any antenna from being 100% efficient.
In real-world applications, a good antenna is considered to be 50% to 60% efficient.
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