Radio Frequency Identification (RFID)

Radio Frequency Identification (RFID)
An Introduction

Prof. David Bernstein
James Madison University

Computer Science Department

bernstdh@jmu.edu

Motivation

The Problem:
- Identify "tagged"/"labeled" objects
The RFID Solution:
- Use a "tag" that uses radio waves to communicate an identification number to a receiver

Components

Tag/Label:
- A simple microprocessor
- A radio transmitter
- An optional (see below) radio receiver
- An optional (see below) power source (e.g., battery)
- An antenna
Reader:
- A microprocessor
- An optional (see below) radio transmitter
- A radio receiver
- An antenna

Classification

Passive Reader, Active Tag:
- The reader only has a receiver
- The tag only has a transmitter
- The tag is "always" transmitting its ID
- The reader receives and processes the ID
Active Reader, Passive Tag:
- The reader transmits interrogation signals
- The tag uses the energy transmitted (not an on-board power source) by the reader to transmit its ID
- The reader receives and processes the ID
Active Reader, Active Tag:
- The reader transmits interrogation signals
- The interrogation signal informs the tag to transmit
- The tag uses an on-board power source to transmit its ID
- The reader receives and processes the ID

Identification Information

Read-Only Tags:
- The ID is assigned at the factory
Read-Write/Field Programmable Tags:
- ID information can be written (once or many times) in the field

Common Frequencies

120kHz - 150kHz (Unregulated):
- Animal "chips"
13.56 MHz (Worldwide ISM):
- Industrial, Scientific, and Medical
- Access Control
- Contactless Smart Cards
433 MHz:
- Defense
865MHz-868MHz (Europe); 902MHz-928MHz (US):
- Electronic toll collection
- Railroad Applications

Options for Passive Tags

Modulation:
- The tag changes the electrical load which can be detected by the reader
Backscatter:
- The tag reflects the signal back to the reader