Radio Frequency Identification (RFID) Systems

Contents

Introduction to RFID Systems
Types of RFID Systems
Operating Frequencies of RFID Systems
RFID Tag Types
Manufacturers and Other RFID Resources

---

Introduction to RFID Systems

A typical RFID system is shown in the figure below. It consists of a tag, a reader, and some sort of data processing equipment, such as a computer. The reader sends a request for identification information to the tag. The tag responds with the respective information, which the reader then forwards to the data processing device. The tag and reader communicate with one another over an RF channel. In some systems, the link between the reader and the computer is wireless.

---

Types of RFID Systems

RFID systems can be classified according to the frequency band in which they operate -- either high, intermediate, or low. RFID systems can further be broken down according to some characteristics of the tags being used, namely, whether the tags are active or passive. And, taking the classification process yet another step further, tags, regardless of whether they are active or passive, can be either read-only, write-once-read-many (WORM), or read-write.

---

The Role of Frequency in RFID

Frequency plays an important role in the design of an RFID system -- it can affect aspects of the system such as operating range and line of sight requirements. The major frequency bands in which most RFID systems operate, along with some of their respective characteristics and applications are summarized in the table below.

Frequency Band	System Characteristics	Example Applications
Low 100-500 kHz	Short read range Inexpensive	Access control Animal identification Inventory control
Intermediate 10-15 MHz	Medium read range	Access control Smart cards
High 850-950 MHz 2.4-5.0 GHz	Long read range High reading speed Line of sight required Expensive	Railroad car monitoring Toll collection systems

---

RF Tag Types

Active tags have an on-board power source, such as a battery. The advantage of active tags is that they reduce the power requirements of the reader, and they can transmit their information over relatively far distances. The disadavantages are that they have a limited operating life, can only be used in certain environments, and are more expensive than passive devices.

Passive tags operate without an on-board power source. They obtain their operating power from energy generated by the reader. They are smaller, lighter, and less expensive than active tags. Furthermore, passive tags have a virtually unlimited life time. Some disadvantages of passive tags are that they have a shorter read range than active tags, and require a much higher-powered reader.

Both active and passive tags can be either read-only, write-once-read-many (WORM), or read-write. Of these, read-write tags are typically the most expensive, while read-only tags are generally the least expensive.

---

RFID Manufacturers and other RFID Resources

Some other useful RFID resources include:

• Transponder News

Transponder News contains general info about how RF ID systems work, some examples of applications of RF ID technology, and a comprehensive list of RF ID suppliers.