How Radio-Frequency Identification Systems Work
How Radio-Frequency Identification Systems Work

Jan 30, 2019

A radio-frequency identification (RFID) system uses tags or labels attached to the objects to be identified. Data stored within an RFID tag microchip waits to be read. The tag’s antenna receives energy from an RFID reader antenna. Using power from its internal battery or the reader, the tag sends radio waves back to the reader. The reader picks up the tag’s radio waves and interprets the frequencies as data. RFID tags broadcast over a portion of the electromagnetic spectrum, and the exact frequency can be selected to avoid interference with other electronics. The reader sends a signal to the tag and reads its response.

The reader has a two-way radio transmitter-receiver, called a transceiver, which transmits an encoded radio signal to the tag. The signal activates the tag, and the transponder then converts the signal into usable power and responds to the reader. The tag receives the message and then responds with its identification and other data. This may be a unique tag serial number or product-related data, such as a batch number. Since tags have unique serial numbers, the RFID system can distinguish several tags in the range of the reader and read them.

Tag Type Determines RFID System

There are currently three different types of tags: active, semi-passive, and passive. An active tag uses its battery to broadcast radio waves to a reader, whereas a semi-passive tag battery is activated in the presence of a reader. Active and semi-passive tags are read over greater distances; they broadcast high frequencies from 850 to 950 MHz that can be read from 100 feet or more. Additional batteries can boost a tag’s range to over 300 feet. Passive RFID tags have no battery and use the radio energy transmitted by the reader as their power source. These tags are read up to 20 feet away and are less expensive. [1,2]

RFID tags consist of three basic parts: an integrated circuit that stores and processes data based on radio-frequency signals, a means of collecting power from the reader’s signal, and an antenna for receiving and transmitting the signal. Tags use either fixed or programmable logic for processing data. They may either be read-only, have a factory-assigned serial number that’s used as a key into a database, or be read/write, where data can be written into the tag by the user. Programmable tags may be write-once, read-multiple; blank tags may be written with electronic product code (EPC).

The type of tag and reader can classify RFID systems: passive reader active tag (PRAT), active reader passive tag (ARPT), and active reader active tag (ARAT). The PRAT system has a passive reader passive, only receiving radio signals from active tags that are battery operated. Its transmit/reception range is from 0 to 2,000 feet (up to 600 m). The ARPT system has an active reader and receives authentication signal replies from passive tags. The ARAT system has an active reader and interacts with active or passive tags awoken with an interrogator signal from the active reader. It can also use a battery-assisted passive (BAP) tag that acts like a passive tag but has a small battery to power the tag’s return reporting signal. Fixed readers create a specific interrogation zone that can be controlled. [1]

How RFID Readers Scan Tags 

The first approach is called bulk grouping; objects that are RFID tagged are read completely from one single reader at one time. However, as tags respond strictly sequentially, the time needed for bulk reading grows linearly with the number of labels to be read. This means it takes at least twice as long to read twice as many labels. Also, if any of the tags are shielded by other tags, they might not be sufficiently activated to return a sufficient response when a single RFID tag may not provide a proper read, a bunch of RFID tags, where at least one will respond, which is better for detecting a group of objects.

The second method is called signaling, and it occurs between the reader and the tag, which depends on the tag’s frequency band. Since they’re only a small percentage of a wavelength away, tags operating on low frequency (LF) and high frequency (HF) bands are near the reader antenna. In this near-field range, the tag is closely paired with the transmitter in the reader. By switching between lower and higher bands, the tag produces a change that the reader can detect. At UHF and higher frequencies, the tag is more than one radio wavelength away from the reader, requiring a different approach. Active tags may respond to a frequency related to the reader’s signal. [1]

Syrma SGS Technology: RFID Experts

We develop RFID hardware and software for asset management, performance metrics, and product authentication. Our comprehensive RFID solutions, products, and services include extensive custom tags, readers, and software. We design, engineer, and manufacture RFID tags in multiple encapsulations spanning all standard wavelengths (LF, HF, and UHF). We also design multi-protocol, custom-made RFID readers compatible with standard tags and connect with iOS and Android devices.

Our versatile USB or audio jack, multi-protocol RFID readers, easily adapting to your PC or mobile device, directly program, scan, and record our tags and transponders. Our readers are compliant with global ISO standards, reflecting 40 years of quality electronics expertise. We can custom-tailor a turnkey RFID solution to meet the precise requirements of any wireless networking application.

Backed by 40 Years of Expertise

We contribute our 40 years of design and manufacturing expertise spanning multiple diverse markets. We look forward to discussing how we can deliver world-class products for OEMs across the globe. We understand our home Indian market, familiar with its vast regulatory and selling environments. We foster growth opportunities within India through our strong technology incubation ecosystem. We also assist global OEMs in entering the Indian market by leveraging the local supply chain and favorable operating environments for cost reductions.

Our flagship Chennai location opened in 2006 and lies within a Special Economic Zone (SEZ) for electronics manufacturing, offering economic incentives for imports and exports. This primary facility is within 90 minutes of the Chennai seaport and 20 minutes to the international airport. Additional road and rail connectivity links to the rest of India and beyond and infrastructure advantages with faster import and export clearances. We also have labor force flexibility, both technical and manual, to scale to demand rapidly.

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