Radio Frequency Identification (RFID) is a hot topic in this digital age of automated tracking and asset management. With all of the different applications for RFID and the various RFID subsets (like NFC), it is easy to get overwhelmed with all of the information. Even something as simple as RFID antennas can be a confusing topic all on its own! The antenna is the component that transmits and receives information between RFID devices. So, they will play an important role as you select the right devices for your RFID system!
So, where should you start on your RFID journey? We always recommend having a clear intent in mind. Knowing what you want to use RFID for will help you narrow down which aspects of RFID will work best for you.
Got your intent in mind? Perfect. Now, let's review the basic concepts of RFID. These key terms will arise as you set up your RFID system, and understanding them will help you select the best devices for your particular intent.
Frequency
Frequency is at the heart of how RFID works. RFID antennas transmit electromagnetic radio waves to read and locate RFID inlays. Radio waves can travel at three different frequencies; Low Frequency (LF), High Frequency (HF), or Ultra-High Frequency (UHF). In terms of waves, amplitude refers to the "height" of a wave, measuring the distance from its resting point to its peak. The more amplitude a wave has, the stronger it is. Wavelength is the "length" of a wave, measuring the distance between two consecutive peaks, representing a single wave cycle. Longer wavelengths will have a lower frequency and vice versa. The frequency is the number of wave cycles passing a fixed point per second, measuring how fast the wave oscillates.

UHF is the most common frequency used as these RFID inlays are the most cost-effective. They have the highest read range but can struggle in some environments. UHF radio waves can struggle to pass through metal or liquids, but LF and HF are more successful in these settings. As a general rule of thumb, the lower frequencies give you the most accurate readings with minimal interference. While the higher frequencies will provide you with the longest read range.
Beamwidth
Distance matters with RFID! Do you intend to use RFID for more targeted-based identification of individual items? Or, for more generalized item counting, where you will need to capture a lot of data at once? The effectiveness of RFID is influenced by the device's beamwidth and gain.
RFID antennas transmit radio waves outward and spread in a cone-like shape. Beamwidth refers to the widest spread of this cone. Simply put, the larger the beamwidth, the more coverage an RFID scanner will have. Gain refers to how effectively an antenna can receive or transmit a signal in a single direction. Generally speaking, the wider your signal spreads, the shorter the distance it can travel. So, the gain will increase with a smaller beamwidth, as a more focused beamwidth will increase the strength of the transfer in a given direction.

Since gain only measures the amount of existing power transferred, decreasing or increasing beamwidth will not affect the overall amount of power used.
Signal Strength
Some RFID devices allow you to adjust the signal strength by modifying the amount of power used to achieve optimal gain. Power is measured in Decibels per Milliwatt (dBm). The higher the dBm, the stronger the signal. Because gain is the overall efficiency of an RFID device in a single direction, we need a standard unit to compare it to. This theoretical unit is called an isotropic antenna. This theoretical antenna radiates power equally (isotropically) in all directions, creating a sphere. When we compare directional gain to the isotropic antenna, the unit is measured in Decibel Relative to Isotropic Gain (dBi), also called Decibels Isotropic.

What does this mean for you? Each device in your RFID system will have its own dBi. It is important to know what kind of dBi will work best for that device. If you intend to read inlays from a distance, getting an RFID scanner and inlay with a higher dBi will be ideal as the signal will be more focused and can travel further. A printer that encodes while it prints would need a more targeted lower dBi to ensure it encodes the correct inlay.
Polarization
Polarization also plays a major role in the success of an RFID system. Signal polarization refers to the orientation of the wave when it is being transmitted through an antenna. Polarized waves travel in a controlled pattern in a specific direction, while unpolarized waves move freely in multiple directions.
When the electromagnetic waves oscillate along a single, consistent plane, it is called linear polarization. This plane could be horizontal or vertical, but the signal always travels in this fixed direction. Because of this, linear polarized antennas have a further read range but work best when the RFID inlay position is known and consistent. Antennas that are not aligned can result in read errors and poor performance.

If you work in an uncontrolled environment where the inlay position may vary, circular polarized antennas will work the best! Circular polarization occurs when electromagnetic waves spin around an axis in a structured, corkscrew-like fashion. This circular motion provides a more consistent reading of RFID inlays, regardless of orientation or position. However, because the signal rotates, the energy will disperse faster, causing shorter read ranges.

Similar to gain and beamwidth, polarization does not relate to the overall energy put into a signal. Linear polarized antennas just yield a more focused path, allowing them to direct the existing energy farther. A circular polarized antenna's energy will dissipate to cover a larger area, making it more versatile, as it can scan tags that may not be within the reader's direct path.
Examples
Are you still confused about how all of these concepts work together? Here are some examples of RFID uses and the ideal RFID antenna for these settings.
Enhance security to control personal access and operations.
Instead of using passwords or key codes, RFID is commonly used to increase security by limiting access. For example, an RFID inlay in an employee badge can be read by the antenna connected to a secured door or equipment.
Ideal Frequency: LF or HF
Beamwidth and Gain: Low beamwidth with high gain
Polarization: Linear
This antenna setup gives a focused, short, and accurate reading without using much energy.
Manage and monitor inventory in a warehouse or retail setting.
Track and locate assets as they move throughout a facility.
Manage loss prevention as items enter or leave a building.
Automate quality control with in-line production monitoring.
The applications of RFID are limitless! These are just a few generalized examples to show how antenna configuration can help RFID perform best in those environments. What problem you intend to use RFID to solve may be different or could be a mix of these examples. For example, retailers that use RFID to manage inventory can encode product expiration dates on their inlays to help monitor quality. The same inlay and scanner used for inventory management also allows them to track and locate expired products, saving them labor costs by automating quality control procedures.
Remember, all RFID devices have an antenna, each is designed to work best in a particular environment to perform a specific task. It is always best to check the spec sheets of the items you want to use in your RFID system to ensure they all work well together. If your printer is designed to encode using HF, UHF inlays will not work with that printer. Or, if you are using a linear polarized scanner in an environment where the inlay position can vary, then you are not going to receive the most accurate readings.
Overall, it is important to know what problem you want to solve with RFID. Environmental factors will play a role in deciding what to use in your RFID setup, but knowing what to look for will help you avoid costly errors and make implementing a new system easier. Still feeling overwhelmed? Contact us if you have any questions! Our knowledgeable Customer Service team will be happy to guide you through the process of ordering what you need for your RFID system! From RFID tags to printers, we've got you covered!