A third final report, on RFID technology

I'm pleased to publish here a third report. Also this report was produced by a student attending my course in TTU. To download the full report, with the missing parts, the figures and the references, just subscribe to my blog as a follower and send me an email.

Tallinn University of Technology

Thomas Johann Seebeck Department of Electronics 

RFID technology

Student : E. P.

Professor: Valerio Alessandroni

Tallinn 2014

History

RFID as idea was first used to identify airplanes during second World War. The idea was to use radar signal for reading airplane identification number. Technology was exclusively used in military during several decades. First patent about RFID tag with memory for tracking was granted in 1973 to Mario Cardullo. Based on that patent, toll collection system was developed for New York Port Authority. Tag was based on ferrite cores and was able to store 16 bit data. For many years RFID tags were used for access control only. Technology development allowed passive tag creation on 80s which led to big price reduction. In 1990s RFID standardization started. Main development target was to get tag price down, less than 1 dollar, which allows use of tags for goods tracking.

RFID market

Main business enablers for RFID were evolution of radio–based technology and supply chain developments. Supply chains with the delivery of product or service are main RFID users as tracking is very important part of supply chain management.

According to (omitted), RFID market was a multibillion market in 2012 ($6.98 billion) and will grow to a (omitted) market in 2020.

This includes passive and active RFID tags, cards, readers and software and services. RFID market has grown steadily despite of economic difficulties in recent years. High growth in recent years came from transit systems and ticketing, safety (biometrical passports tagging) and from animal tagging. Total of 4.8 billion tags were sold in 2012 and 5.9 will be sold in 2013 according to (omitted). Biggest growth is expected from (omitted) which needs 2.25 billion RFID labels in 2013. Many suppliers are finally profitable and see rapid growth in the future. There are not any significally big players in the RFID market – from more than 800 suppliers only eight having revenues more than $100 million and around 20 having sales between $20 to $100 million.

Biggest public RFID companies and their business descriptions: (omitted)

RFID technologies

RFID tags can be classified in many different ways – what kind of technology it uses, is it active or passive, can data be written into it, what kind of frequency or modulation scheme it uses etc. One clear classification is tags with silicon chip and tags without it. Tags without the chip are obviously cheap but their usability is not so wide.

 Most common tag is the (omitted) tag which is used to prevent shoplifting, stealing of books from library or items from office buildings. It is known also as 1 bit RFID and that bit indicates if tag is present or not. There is no possibility to code any information into the tag. Tag itself is actually resonant LC circuit, usually with resonant frequency of 8.2MHz. Tag reader can detect the presence of the tag in RF field as it starts transmitting on its resonant frequency. Deactivation of the tag can be done in strong RF field which will destroy capacitor in LC circuit. 

Another chipless tag is based on (omitted). This tag is passive and cheap but it is possible to code specific ID code into it during manufacturing. Code length is usually tens of bits.

During the reading reader will excite tag with RF field generating soundwave in the crystal, when the soundwave is reflecting back it generates RF signal. Signal delay times can be adjusted by reflector positions in the device and reader can detect tag specific ID code.  

Tags with the chip have much better capability, they can have memory tens of kilobytes, microprocessor for sophisticated communication, encryption, anti-collision features etc. That kind of tags can be divided into the cheap state machine tags and tags with microprocessor. State machine tags are using simple communication protocol and they can have read-only or writable memory. This kind of tags are used for access control, asset tracking, monitoring, process control, animal tagging etc.

Tags with microprocessor are used in smartcards, security systems, biometric passports or other places where privacy, data integrity, high security and data encryption is required.

RFID tags are often divided into active, semi-active or passive tags. Active tags have their own RF transceiver embedded. They can send signals autonomously, make measurements, act as sensors or they can receive external commands and act accordingly. This type of tags consume much more energy and usually have their own internal power source embedded. 

Semi-active tags or battery assisted passive tags have embedded battery on board for sensors. Tag itself doesn’t have active RF transmitter, battery is only for energy what tag needs between reading cycles.

Passive RFID is most common tag in the market. Passive tag backscatters magnetic or electromagnetic waves from reader. These tags do not have RF transmitters and they can’t generate their own RF field. Tag is using incoming signal from reader to power up embedded chip. Passive tags can divided to Near-field RFID or Far-field RFID tags. Near-field approach is using lower frequencies and Faraday’s effect of magnetic induction coupling between reader and the tag. Reader generates high alternating current through the coil, resulting alternating magnetic field around the coil. Passive tag has embedded coil which is used for coupling and it generates voltage which will be rectified and used for charging power capacitor. Voltage in capacitor is used to power up tag electronics. Communication back to the reader is achieved through the load modulation technique.

Near field coupling is the easiest approach for implementing passive RFID system. It was first approach and used in most access systems and animal tagging solutions. It uses lower frequencies, usually 125kHz or 13.56Mhz. Unfortunately it has some limitations – Near-field coupling range is function of frequency and it is decreasing with frequency. Another problem is that magnetic field drops off at the rate of r³ where r is distance from reader to the tag. It means that tag should be well aligned with reader. Applications which need higher data rate and discrimination between multiple tags are using different technology like Far-field approach. Far-field tags are based on electromagnetic wave emissions from dipole antenna attached to the reader. Tag has smaller dipole antenna which receives energy, rectifies it with diode and charges capacitor. Unlike the inductive design information cannot be sent back using load modulation. Communication is based on back-scattering – in case of tag antenna impedance mismatch it will reflect some energy back to the receiver. So, communication back to the reader is done by modulating antenna impedance. 

Far field tags have to use higher frequency to get better antenna efficiency – frequency is higher than 100MHz, usually around 900MHz or 2.4GHz. Range is limited by amount of energy tag can receive. Energy is decreasing at the rate of r² in tag direction but backscattering energy is decreasing at the rate of r⁴ which means that receiver has to be very sensitive.

Range and read speed properties of passive tags: (omitted)

Mechanical construction of the tags depends on application and varies a lot. Commonly used tags are discs, coins, glass housing pills, plastic housing, keys, clocks, smart labels, coil on chip micro-tags.

Standardization and protocols

(omitted)

Recent developments

(omitted)