There are a handful of factors that can affect RFID, NFC, or UHF tag read ranges. If you're interested in understanding the various aspects that affect RFID read range to improve your RFID application or use case, continue reading!
Tag Characteristics (SOAP)
SOAP is an acronym for the various factors that affect an RFID tag's performance; size, orientation, angle, and placement.
Inlay Size — As a rule of thumb, the bigger the tag inlay, the longer the read range. Of course, it is important to remember that the variation of reading ranges determined by the tag inlay size is within the constraints of the tag type and frequency (e.g., HF, LF, UHF).
Orientation — Orientation, or tag rotation, isn't a factor for tags that have circular polarized antennas. However, tags that have an antenna with linear polarization, orientation affects the reader's ability to effectively read the tag's data.
Angle — Read angle is an especially important consideration when the reader is mounted. It's vital to make sure that the reader is placed/oriented in a way that facilitates easy access to the optimal read angle. Reading a tag from an angle opposed to a direct line of sight will negatively impact that read range of the tag. Information regarding reading angles is typically found in the specifications or user manual of the RFID reader.
Tag Placement — Tag placement can make a huge difference in the read range of the tag; there are many, many environmental factors can generate interference that will adversely affect various types of RFID technology, including other RFID devices/tags, conductive materials, fluorescent lighting, machinery, water, and other technologies/equipment that use frequencies that overlap with the type of RFID tag you are using. For example, a regular tag placed on a conductive surface (e.g., a metal surface) will have significantly shorter read ranges, if you can read it at all.
Tag Type — Additionally, the tag type will also affect the read range. Active tags, while significantly more expensive than passive tags, typically have a longer read range than their passive counterparts.
The frequency range of an RFID system has a significant impact on the read range. Generally speaking, the higher the frequency, the longer the read range. That being said, a shorter read range isn't always a bad thing. For example, NFC is used for smart card and payment application because of the short read range of NFC (hence the name "near field communication") is implemented as a security feature. You wouldn't want a reader to be able to read the data from your credit card from more than a few centimeters away for obvious reasons.
The chart below shows the read range differences across the common RFID frequency ranges.
|RFID Frequency Band||Read Distance|
|Low Frequency (LF/NFC)||< 10 cm|
|High Frequency (HF)||< 1 m|
|Ultra-High Frequency (UHF)||1 - 100 m|
Although most smartphones today have RFID/NFC reading capabilities, they are optimized for minimal power consumption; this results in a much shorter read range compared to RFID readers such as the idChamp RS3 and RS4. Additionally, embedded smartphone readers are limited to only reading data from a select number of data store types (excluding proprietary data stores typically used in business applications), whereas the RS3/RS4 are not limited in these ways—they can read and write both common/open data stores and proprietary ones.
Reader Power and Sensitivity Settings
Many RFID readers/writers, including the idChamp RS3 and RS4, allow you to adjust the reader's power consumption and sensitivity to nearby tags. For Serialio's RS3 and RS4, you can change the various settings, including the reader power/sensitivity, with the RS3 NFC Setup application for iOS and Android. Alternatively, you can use RFIDeas' pcProx Configuration Utility for Windows.