RFID (Radio Frequency Identification): A Tutorial

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RFID (Radio Frequency Identification): A Tutorial

Contents:

1. Introduction to Radio Frequency Identification-RFID
1. What is RFID
2. Compare RFID with Bar Code Technology
3. Benefits of RFID
4. Disadvantages of RFID
2. Active and Passive RFID Systems
3. RFID Frequencies
4. Operation of RFID Systems
   1. RFID Building blocks
   2. RFID Tag block schematic, and operation
   3. Backscatter Modulation
5. RFID Standards
6. RFID Manufacturers
7. Applications of RFID
8. RFID Test Labs:
9. RFID Implementations
10. RFID Glossary of Terms

Active and Passive RFID Tags:

There are primarily two types of RFID tags.

One is active and the other is passive.

An active tag is powered using internal battery, where a passive tag gets energized using a the power from a tag reader.

A passive RFID tag will not have a battery or any kind of power source by itself.

It extracts the required energy from a reader.

Hence, a passive RFID tag reader must be able to emit stronger electromagnetic signals,

and in return, identify very weak signals from the passive RFID tag.

Given below are the primary differences between a Passive and Active RFID tags:

RFID Frequencies:

There are several frequencies that are used for RFID.

These include LF, HF, UHF, and Microwave frequencies.

The exact frequencies may vary depending on the country where it is used.

1. Operation of RFID Systems

   1. RFID Building blocks
   2. RFID Tag block schematic, and operation
   3. Backscatter Modulation

a. RFID Building Blocks:

Tags: A tag is the data carrier and normally contains the ID number, and unique EPC code programmed into the Tag
Tag Antenna: The tag antenna is connected to the chip in tag. It could be wire or printed using conductive ink.
Reader Antenna: It is a coil included in plastic or similar case, and normally measures 12 -18 inches square
Reader: A reader captures the data provided by the tag within the detectable area of the Reader. There can be one or more tags within the capture area. A reader is typically capable of reading multiple tags simultaneously.
Savant: This is normally a middleware that interacts with the readers, and communicate with External databases.

b. RFID Block Schematic:

A simplified block schematic of an RFID tag (also called transponder) is shown in the diagram below. Various components of the tag are as shown. Normally, the antenna is external to the tag chip, and large in size.

The operation of the RFID tag is described below:

Handshaking with the Reader (interrogator):

• The reader continuously emits RF carrier signals, and keeps observing the received RF signals for data.
• The presence of a tag (for our discussion, we consider only passive tag) modulates the rf field, and the same is detected by the reader.
• The passive tag absorbs a small portion of the energy emitted by the reader, and starts sending modulated information when sufficient energy is acquired from the rf field generated by the reader. Note that the data modulation (modulation for 0s and 1s) is accomplished by either direct modulation or FSK or Phase modulation.
• The reader demodulates the signals received from the tag antenna, and decodes the same for further processing.

c. Backscatter Modulation:

Backscatter is one of the most widely used modulation schemes for modulating data on to rf carrier. In this method of modulation, the tag coil (load) is shunted depending on the bit sequence received. This in turn modulates the rf carrier amplitude as shown in the diagram below. The reader detects the changes in the modulated carrier and recovers the data.

The above diagram provides a simplified modulated carrier signals from the RFID tag.

As seen in the diagram, the encoded binary digits modulate rf carrier.

A 1 is represented with high carrier level, and a 0 is represented by a low carrier level (tag coil shunted).

The reader demodulates the signals to recover the data, and note that this data is still encoded.

The reader decodes the data using suitable decoder, and forwards it for further processing to a computer (or any backend server).

Applications of RFID:

1. Employee Identification and Access Control
2. Airline baggage Identification
3. Wafer Identification during manufacturing process
4. Livestock Identification
5. Parts Identification
6. Identification and Tracking of Vehicles
7. Identification of  widgets through manufacturing process
8. Supply Chain Automation
9. Asset Tracking, and others.

RFID (Radio Frequency Identification): A Tutorial

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原文地址：http://www.cnblogs.com/shangdawei/p/4827806.html