Is HF or UHF industrial RFID better?

Industrial manufacturing is constantly adapting to meet the ever-increasing productivity and efficiency demands on the factory floor, and track-and-trace technologies play an important role in satisfying these goals. Radio frequency identification (RFID) has been providing manufacturers with high-quality monitoring systems to deliver unparalleled control and visibility over automated operations for increased efficiency gains and improved production.

With each industrial application presenting a unique set of challenges and demands, it is important to know the speed, range, and number of tags individual operation requires to achieve the necessary level of control. Know the strengths and weaknesses of high-frequency (HF) and ultra-high-frequency (UHF) RFID, and identify the industries and applications that suit each technology best.

High frequency vs. ultra-high frequency

HF RFID is among the most commonly used track-and-trace technologies in industrial applications, and is often implemented because of its reliable operation. HF RFID tags use inductive coupling to communicate between read/write heads and transponders. The reader emits a magnetic field, and when a transponder passes through, an electric current is created that powers the RFID tags and transmits data. 

Inductive coupling creates a well-defined magnetic field that is smaller but easier to control. With high-frequency systems, the strength of the signal is dependent on the distance from the antenna. This accounts for its short-range operation, reaching up to 50 cm. HF RFID has an operating frequency of 13.56 MHz and can accommodate read-only, write-only, and rewritable tags, with a memory capacity from 64 bytes to 8 KB and can handle up to 20 tags at one time. Further, the amount of memory on the tag determines the amount of data that can be stored, and to accommodate various application requirements, tags are available in many different shapes, sizes, and materials.

Ultra-high frequency

Unlike HF RFID, UHF RFID offers near-field and far-field read ranges. Near-field RFID operates similarly to HF RFID, where the antennas generate a magnetic field. Since the tag is closer to the antenna, near-field UHF has a narrower field of view and a shorter read range (comparable to HF RFID). For an additional performance advantage, near-field UHF features an antenna that reduces magnetic shielding, enabling it to block visibility of other tags in close proximity.

Far-field UHF uses electromagnetic waves propagating between reader and tag antennas, delivering a wider field along with an increased possibility for interference. While able to accommodate high speeds and longer read distances, far-field UHF technology is more complex and the performance of the RFID system gradually degrades because of its absorption, refraction, and reflection properties.

Using radio waves to communicate between the read/write head and the tag, UHF RFID can accommodate long-range application requirements, as the electric field features strength that extends much further than possible with high-frequency options. Capable of communicating over several meters with an operating frequency between 860 and 960 Mhz in the far-field, UHF RFID can solve fast-paced, complex applications that require multiple tags to be read simultaneously—handling as many as 200 tags at a time.

– Turck provided this article, edited by Mark T. Hoske, content manager, CFE Media, Control Engineering, Plant Engineering, and Consulting-Specifying Engineer, mhoske@cfemedia.com.

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