What is RFID?

Radio Frequency Identification (RFID) is a generic term for technologies that use electromagnetic field or radio waves to automatically identify people and objects. Wireless communication takes place between a reader (sometimes interrogator) and a small transponder called tag.

RFID is a technology often seen as a descendant of the ubiquitous barcode, which has been used since the late 1960's as a printed means of identifying product categories. Unlike barcodes, no clear line of sight is required to obtain an accurate read. There are different versions of barcode technology (EAN, JAN) encompassing 8 to 14 digit systems and same coding schemes can be combined for RFID.

The basic RFID system comprises a tran­sponder, a reader and an antenna. Data is stored in a tag. Current tags, depending on applica­tion, can hold up to 64 kilobits of data. Tags can be read-only, one time programmable or read/write.

A radio frequency signal is transmitted from the reader to a transponder that passes within range of the reader's antenna. The signal triggers RF emissions from the tag. The transponder holds bits of data, which is either reflected or sent back to the reader, depending on whether the tag is passive or active. Transponder data includes information such as the transaction record type, the unique transponder ID number, the reader ID number, the transaction status code, and the error detection code. Customer data can be specified as well.

 

Glossary
 

Source of tag power

Tags can be passive (powered by radio frequency field of the reader), semi-passive (powered by a small battery) or active and they comes in various forms including smart cards, encapsulated tags, labels, watches and even embedded in mobile phones. Active tags, which have a longer read range, have a trans­mitter to send back information, rather than reflecting the signal back to the reader. Used to power the transmissions in active tags, the battery adds significantly to the tag cost, and limits the tag life to the battery life. Semi-passive tags also use the battery to power the circuitry, but not the broadcast signal. Sensor functionalities can also be added to tags.

Frequencies

The communication frequencies used in RFID system depends on the application requirements. Range of frequencies starts from 125 kHz (LF) and normally end at 2.45 GHz. Regulations are imposed by most countries (grouped globally into 3 regions) to control emissions and prevent interference with other professional communication systems and Industrial, Scientific and Medical equipment (ISM). You can find the updated frequency regulations from here.

Read range

The read range, or the physical area within which the reader can recognize the tag, is dependent on several factors including the tag-reader frequency, antenna design for both tag and reader, tag energy efficiency and amount of illumination field strength (transmitter power) generated by the reader. Antenna-to-tag orientation issues are impacted by the antenna polarization method used (circular vs. linear). Antenna sizes are mostly a function of the operating frequency used.

Middleware

Middleware is the software interface between the reader hardware and the existing company databases and information management software. It implements the different reader interfaces and protocols and manages the data flow to the application software. The middleware has to take into account the distributed nature of RFID applications. The distributed architecture of typical RFID applications demands on the other hand networking capabilities on the reader side. Thus the middleware functions are implemented more and more inside the reader.

Encoding

Data stored in RFID tags depends on the application and existing standards. For example, the design of EPCglobal-supported code is divided into four sections (header, manager number, object class and serial number). Although many current RFID applications are based on proprietary systems, industries support­ing open RFID systems with open standards may soon proliferate.

EPC

Electronic Product Code is a standard code for RFID tags administered by EPCglobal Inc. The EPC number, which can be from 64 to 256 bits, contains at least the following fields:

  • EPC version
  • Company identification number assigned by EPCglobal
  • Product number (object class)
  • Unique serial number. A 96-bit EPC is capable of differentiating 68 billion items for each of 16 million products within each of 268 million companies.
  • Unlike UPC bar codes, which do not have serial numbers, the EPC enables tracking of individual items because every item can be uniquely identified.