Radio-frequency identification

Introduction

Radio-frequency identification (RFID) is a communication technology, that uses electromagnetic waves to identify and track tags. A RFID system consists out of a tag, which is attached to an object, an reader, which extracts the information of the tag and an application, that uses the gathered information.

RFID-System

Reader

A reader is responsible for initiating the communication with a tag, in case of a passive tag the reader also supplies the energy needed to operate the tag. A reader consists out of to components:

1. A control unit
2. A high-frequency interface

Control Unit

The control unit is responsible for

1. Communication with the application
2. Communication with the tag
3. Coding and decoding of the signal
4. Anti-collision algorithm
5. Encryption and decryption of data sent between reader and tag
6. Authentication between reader and tag

High-frequency interface

The high-frequency interface is responsible for

1. Generation of strong high-frequency signals to activate the tag and supply it with energy
2. Modulating the transmission signal to send data to the tag
3. Receiving the radio frequency signals transmitted by a tag and converting them back into original data

Tag

RFID tags are divided into six categories by EPC Global. A tag in one category has all the capabilities of the subordinate categories. This means that tags are backward compatible

Passive tags, which have no built-in energy source and draw their energy from the reader's radio waves, are assigned to classes 0 to 3. Active tags, with their own energy source, are assigned to class 4. Class 5 is reserved for tag readers and active tags that can read other tags.

1. class 0: These tags are passive and work with UHF. These tags are pre-programmed in the manufacturer's factory and can no longer be reprogrammed, the information can no longer be changed.
2. Class 1:Class 1 tags use HF radio waves. In contrast to class 0 tags, class 1 tags and higher can be programmed by the user. However, in class 1, tags can only be described once.
3. Class 2: Unlike class 1, class 2 tags can be written to multiple times.
4. Class 3: Read-write with integrated sensors that are able to detect parameters such as temperature, pressure and movement; can be semi-passive or active. Semi-passive means that they occupy an energy source but cannot initiate communication with other tags or readers.
5. Class 4: Class 4 tags have their own energy source and can initiate communication with other tags or readers, so they are active tags.
6. Class 5: Class 5 tags are the most advanced, they can transfer energy to passive tags and communicate with readers and tags of any class, so they can also be classified as readers.

RFID tag information

Four types of information can be stored on a transponder:

1. Information to identify the tagged item: This category includes the identification data used to uniquely identify the tagged item. This includes user-defined fields such as bank accounts, product barcodes and prices, as well as predefined registers such as the Application Family Identifier (AFI) and the Data Storage Format Identifier (DSFID)
2. Supplementary information on the object: Supplementary data includes further standard information such as Application Identifiers (AIs) and ANSI MH-10 Data Identifiers (DIs), which enable further differentiation and specific information on the tagged item
3. Control data: Control data could include information about the configuration of the tag, such as the settings for the security controls, including mechanisms that restrict reads or writes to user memory blocks and special registers that contain the AFI and DSFID values
4. Manufacturer data: The unique identifier (UID), transponder type, manufacturer and manufacturing data can be stored in this category. This information can be specific to each manufacturer and transponder type.

The first two categories, identification and supplementary information, are present on all tags as they provide essential information for identifying and supplementing the tagged item. Categories three and four, control data and manufacturer data, can vary depending on the manufacturer and contain specific information for configuring the tag and identifying the manufacturer.