Overview of RFID Technology

RFID is an acronym for Radio Frequency IDentification. It is a technology in which objects can be identified through the tags associated with the object. The information exchange is achieved through radio communication between the RFID tag and the reader. The advantage of RFID system for object detection over barcode or QR system is that it does not need a line of sight interface between the object/tag and the reader.  

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Basic Components in a RFID System:

The following fundamental components are present in every RFID system:

1. RFID Tag – It is the fundamental component which is required in a RFID system. Each object is associated with a tag and can be identified amongst other similar other objects using the tag.  A RFID tag consists of a silicon microchip which is attached to a small antenna. It is mounted on a substrate and encapsulated in different materials like plastic or glass veil. It might also have an adhesive on the back side so that it can be attached to objects. The RFID tag consists of a transponder, rectifier circuit and a memory unit where data is stored. Tags come in various shapes and sizes and can be selected based on application.               Image credits - All About Electronics, Google Images
2. RFID Reader – It consists of antennas to receive and transmit waves and is responsible for the communication and helps to read the data stored in the tag. It continuously sends radio waves and can also detect multiple objects at the same time. This is an advantage over barcode where only one object can be read at one time and Line of Sight is required. It can be as small as a hand held device or can be as large as a door.

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Types of RFID Tags:

There are two other common classifications of tags, depending on how the tag communicates with the reader: passive or active.

I.     Active RFID

Active RFID tags have their own transmitter and power source usually a battery onboard the tag. These are mostly UHF solutions, and read ranges can extend up to 100 m in some instances. Active tags are usually larger and more expensive than their passive counterparts and are used to track large assets (like cargo containers, vehicles, and machines). Active RFID tags are also often equipped with sensors that measure and transmit temperature, humidity, light, and shock/vibration data for the objects they are attached to.

There are two types of active tags. Transponders only “wake up” and transmit data when they receive a radio signal from a reader. For example, a transponder attached to a vehicle in a toll payment or checkpoint control location would only be active when passing through a particular gate. This helps conserve battery life.

Beacons, on the other hand, emit a signal at a pre-set interval. This type of active tag is used in real-time location systems (RTLS) for tracking anything from wheelchairs at a hospital to large cargo containers at a shipping dock.

II.    Passive RFID

In passive RFID solutions, the reader and reader antenna send a signal to the tag, which is used to power the tag and reflect energy back to the reader. There are passive LF, HF, and UHF systems. Read ranges are shorter than with active tags and are limited by the power of the radio signal reflected back to the reader (commonly referred to as tag backscatter).

Passive tags are usually smaller, less expensive, and more flexible than active tags. This means they can be attached or even embedded on a wider variety of objects. Passive UHF tags are commonly used for item-level tracking of consumer goods and pharmaceuticals, for example.

III.    Battery-Assisted Passive RFID

A third, hybrid type of RFID tag has also emerged. BAP systems, or semi-passive RFID systems, incorporate a power source into a passive tag configuration. The power source helps ensure that all of the captured energy from the reader can be used to reflect the signal, which improves read distance and data transfer rates. Unlike active RFID transponders, BAP tags do not have their own transmitters.

 Differences between the various types of tags have been enlisted below : 

	Active RFID	Passive RFID	BAP RFID
Tag Power Source	Internal to tag	Energy transfer from the reader via RF	Tag uses internal power source to power on, and energy transferred from the reader via RF to backscatter
Tag battery availability of tag power	Yes continuous	No only within field of reader	Yes only with in field of reader
Required signal strength from reader to tag	Very low	Very high	Moderate
Available signal strength from tag to reader	High	Very low	Moderate
Communication	Long range-100m and more	Short range-up to 10m	Moderate range-up to 100m
Sensor capability	Ability to continuously monitor and record sensor input	Ability to read and transfer sensor values only when tag is powered by reader	Ability to read and transfer sensor values only when tag receives RF signal from reader

Working Principle

There are two waves in which the information exchange can take place between the RFID tag and the reader: 1) Inductive Coupling method 2) Electromagnetic back-scatter method.

Inductive coupling method: It is used for low frequency applications typically in the kHz or MHz frequency band. As the frequency is low, the range is low as well. Read/Write or Read only operations can be performed. Transmission range is less than 1 meter. Passive tags are used. The RFID tag receives power from the reader using inductive coupling. The reader consists of a coil connected to an AC supply such that a magnetic field is formed around it. The tag coil is placed in the vicinity of the reader coil and an electromotive force is induced it by the virtue of Faraday’s law of induction. The EMF causes a flow of current in the coil, thus producing a magnetic field around it. By the virtue of Lenz law, the magnetic field of the tag coil opposes the reader’s magnetic field and there will be a subsequent increase in the current through the reader coil. The reader intercepts this as the load information. This system is suitable for very short distance communication. The AC voltage appearing across the tag coil is converted to DC using rectifier and filter arrangement. 

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Electromagnetic Backscattering method: It is used for high frequency applications typically in upper MHz bands or GHz bands. Due to high frequency of operation, the range is high. It supports read only as well as read/write operations. The tags can be passive, active or semi passive. The transmission range is more than 1 meter and increases as higher frequency of operation is used. The antenna present in the reader transmits electromagnetic waves which are received by the antenna present in the tag as potential difference across the dipole. This voltage is rectified and filtered to get the DC power. The receiver antenna is kept at different impedance which causes it to reflect a part of the received signal. This reflected signal is received by the reader and monitored accordingly. 

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Advantages of RFID System:

1. Automates data collection.
2. Significantly reduces human effort as well as error.
3. Line-of-sight access is not needed.
4. Multiple RFID tags can be read at the same time, thus increasing efficiency.
5. Available scanners support both RFID as well as barcoding, which provide flexibility of operation.
6. Objects can be easily tracked.

Disadvantages of RFID System:

1. Scanning multiple tags is not always a boon especially when you want to selectively read only specific items.
2. There are certain material limitations. Some materials do not provide an accurate or reliable scan as they cause interference with the antenna or may completely deactivate it.
3. RFID can be significantly costlier than other contemporary systems.
4. Implementation of a successful RFID system requires careful planning and a lot of time and money has to be invested.

Applications of RFID:

1) Product tracking and Inventory control: 

It provides better and faster solution for bundling, labeling, identification product safety and product tracking. The stored information remains readable in extreme operational environment at any time. RFID tags over simple bar code provide a unique and safe alternative. Each RFID tag if programmed with unique code. RFID enabled systems have provided to have better cost solutions, less man power and increase timely delivery.

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2) Toll Road payments: 

RFID tags placed in the windshield of automobile vehicles such as cars, trucks, etc. Make highway road toll payments more convenient and faster. FASTAGS was an RFID based toll payment system initiated by Government of India. It showed beneficial promise and wide range of applications. This sort of RFID based online mode of payment has many advantages: 

1. It is faster. Hence, waiting time on toll booth is less which prevents chaos at peak hour.
2. It is safer. Online transactions undergo severe safety measurements from banks. Which you are not at risk of any fraud type activity. Or any cyber type risk. Some banks offer cash-backs which helps in saving money if someone is a frequent traveler.
3. RFID based toll payment tags predict saving on fuel consumption for over 12,000 Cr (INR).

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3) RFID in passports: 

In the US since 2007 a small RFID chip was embedded in all passports which contained all contact information about the person. When they are presented in front of a radio frequency scanner the scanning device provides enough energy to transmit the information. This technology had been implemented because of security measures since the devastating terrorist attacks.

4) RFID to check attendee: 

RFID tags takes out the necessity for queues in an event. The tag embedded would be detected from 10 feet long distance from a radio frequency which makes event management convenient, faster and more accurate. It helps in crowd management.

By

Sarvesh Patki, 

Aaron Matthew, 

Nupur Gadhe, 

Chinmay Pathak

References:

1. https://www.slideshare.net/akdude25/rfid-coupling
2. https://www.youtube.com/watch?v=Ukfpq71BoMo
3. https://en.wikipedia.org/wiki/Radio-frequency_identification