Handbook of Smart Antennas for RFID Systems

Nemai Chandra Karmakar, Nemai Chandra Karmakar

• Publisher: Wiley-Interscience
• Year: 2011
• ISBN:
  9781118074398
• Edition: 1
• Topic: Tecnologia e ingegneria
• Subtopic: Comunicazioni mobili e wireless

The Handbook of Smart Antennas for RFID Systems is a single comprehensive reference on the smart antenna technologies applied to RFID. This book will provide a timely reference book for researchers and students in theareas of both smart antennas and RFID technologies. It is the first book to combine two of the most important wireless technologies together in one book. The handbook will feature chapters by leading experts in both academia and industryoffering an in-depth description of terminologies and concepts related to smart antennas in various RFID systems applications. Some topics are: adaptive beamforming for RFID smart antennas, multiuser interference suppression in RFID tag reading, phased array antennas for RFID applications, smart antennasin wireless systems and market analysis and case studiesof RFID smart antennas. This handbook will cover the latest achievements in the designs and applications for smart antennas for RFID as well as the basic concepts, terms, protocols, systems architectures and case studies in smart antennas for RFIDreaders and tags.

PART I

INTRODUCTION TO RFID

CHAPTER 1

THE EVOLUTION OF RFID

BEHNAM JAMALI

School of Electrical and Electronic Engineering, University of Adelaide

1.1 INTRODUCTION

Radio-frequency identification (RFID) is a relatively new technology. Some believe that its concept might have originated in military plane identification during World War II and that it really started to be intensively developed for tracking and access applications during the 1980s. These wireless systems allow for noncontact and non-line-of-sight reading of data from electronic labels by the means of electromagnetic signals, and consequently they are attractive for numerous tracking and tagging scenarios. For example, they are effective in hostile environments such as manufacture halls, where bar code labels could not survive. Furthermore, RFID tags can be read in challenging circumstances when there is no physical contact or direct line of sight. RFID has established itself in a wide range of markets, including livestock identification and automated vehicle identification systems, because of its ability to track moving objects. RFID technology is becoming a primary player in automated data collection, identification, and analysis systems worldwide.

RFID, its application, its standardization, and its innovation are constantly changing. It is a new and complex technology that is not well known and well understood by the general public, or even by many practitioners. Many areas of RFID operation need development to achieve a longer reading range, larger memory capacity, faster signal processing, and more secure data transmission.

1.2 ELECTROMAGNETIC TIMELINE

In this section we will provide an anecdotal history of the most important electromagnetic personalities in chronological order. A short biography of each scientist is also provided along with their main contribution to this field

Charles-Augustin de Coulomb (1736–1806) was a military civil engineer, retired from the French army because of ill health after years in the West Indies. During his retirement years he became interested in electricity and discovered that the torsion characteristics of long fibers made them ideal for the sensitive measurement of magnetic and electric forces. He was familiar with Newton’s inverse-square law, and in the period 1785–1791 he succeeded in showing that electrostatic forces obey the same rule.

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Luigi Galvani (1737–1798) was an Italian physician who, in the 1770s, began to investigate the nature and effects of what he conceived to be electricity in animal tissue and of muscular stimulation by electrical means. He discovered that contact of two different metals with the muscle of a frog resulted in an electric current.

Alessandro Giuseppe Antonio Volta (1745–1827) was a professor at the University of Pisa. He was a close friend of Galvani. After he heard about Galvani’s discovery, Volta began experimenting in 1794 with metals alone and found that animal tissue was not needed to produce a current. His invention and demonstration of the electric battery in 1800 provided the first continuous electric power source.

Hans Christian Oersted (1777–1851) was born in a village without a school. He was educated by the villagers and went on to become a professor at the University of Copenhagen. In 1820 he was performing a classroom demonstration of the heating effect of electric currents when he observed the deflection of a nearby compass. He had discovered a connection between electricity and magnetism.

Andre-Marie Ampere (1775–1836) learned about Oersted’s discovery in 1820 that a magnetic needle can be deflected by a nearby current conducting wire. He then prepared within a week the first of several papers on the theory of this phenomenon, formulating the law of electromagnetism, known as Ampere’s Law, which describes mathematically the magnetic force between two current-conducting elements.

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Jean-Baptiste Biot (1774–1862), along with Felix Savart, formulated the Biot–Savart law of magnetic fields:

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Karl Friedrich Gauss (1777–1855) ranks as one of the greatest mathematicians of all time. Beginning in 1830, Gauss worked closely with Weber. Gauss lived to an advanced age; and having systematically studied the financial markets and invested accordingly, he died a very wealthy man. Gauss’ law of electrostatics states that the total electric flux through a closed surface is proportional to the total electric charge enclosed within the surface:

(1.4)

Michael Faraday (1791–1867) was born in a village near London. Faraday became the greatest experimentalist in electricity and magnetism of the nineteenth century. He produced an apparatus that was the first electric motor, and in 1831 he succeeded in showing that a magnet could induce electricity. Faraday’s law of induction describes an important basic law of electromagnetism:

(1.5)

James Clerk Maxwell (1831–1879) is ranked with Newton and Einstein for the fundamental nature of his many contributions to physics. Most importantly, he originated the concept of electromagnetic radiation, and his field equations (1873) led to Einstein’s special theory of relativity. In classical electromagnetism, Maxwell’s equations are a set of four partial differential equations that describe the properties of the electric and magnetic fields and relate them to their sources, charge density, and current density. Maxwell used the equations listed in Table 1.1 to show that light is an electromagnetic wave.

TABLE 1.1 Maxwell’s Equation

Heinrich Rudolf Hertz (1847–1894), a German physicist, was the first to broadcast and receive radio signals. He applied Maxwell’s theories to the production and reception of radio waves. In 1884, He rederived the Maxwell’s equations by a new method, casting them in modern form as shown in Table 1.1. He produced electromagnetic waves in the laboratory and measured their wavelength and velocity. He showed that the nature of their reflection and refraction was the same as those of light, confirming that light waves are electromagnetic radiation obeying Maxwell’s equations.

Guglielmo Marconi (1874–1937), an Italian physicist, is the inventor of radio. He was granted a patent for a successful system of radio telegraphy in 1896. In 1909 he received the Nobel Prize in Physics. Marconi’s great triumph was in 1901, when he successfully received radio signals transmitted across the Atlantic Ocean. This sensational achievement was the start of the vast development of radio communication and broadcasting the way we know it today.

1.3 RADAR

The use of electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects was first contemplated in the early 1900s. The term RADAR was coined in 1941 as an acronym for radio detection and ranging [1].

A radar system consists of a transmitter that emits either radio waves that are reflected by the target and detected by a receiver, typically in the same location as the transmitter. Although the signal returned is usually very weak, the signal can be amplified. This enables radar to detect objects at ranges where other emissions, such as sound or visible light, would be too weak to detect. Radar’s potential in determining the speed and position of an object was quickly understood by the military, leading to its significant development during World War II era.

1.4 GENESIS OF RFID

Many authors date the origin of RFID to the 1940s during World War II. The Germans discovered that if their pilots rolled their planes as they were approaching their base, they could establish a secret handshake. The roiling of the planes modulated the reflected radar signal. The British, on the other hand, developed the first active identify friend or foe (IFF) system [2]. They placed a transmitter on each British plane that upon detecting a radar signal would broadcast back a signal that would identify the aircraft as friendly. An RFID system basically works on the same principles. A base station (RFID reader) sends a signal to a transponder (tag) that either reflects back the received signal (passive RFID) or broadcasts a signal back to the reader (active RFID).

A major milestone toward modern RFID was the work by Harry Stockman in his 1948 paper, entitled “Communication by Means of Reflected Power.” Stockman stated in his paper that “…considerable research and development work has to be done before the remaining basic problems in reflected-power communication are solved and before the field of useful applications is explored [3].” The discovery of semiconductor transistors in the 1950s enabled Stockman’s vision of reflected power-coded communication to become a reality.

The main era of exploration of RFID technology began in the 1950s by work done by F. L. Vernan [4] and D. B. Harris [5]. The first patent on RFID technology was granted to Mario Cardullo in 1973 [6]. Cardullo’s invention was the first true ancestor of modern RFID: “A passive radio transponder with memory.” Cardullo’s RFID tag was designed to be used as a toll device, and there were a number of potential users, including the New York Port Authority.

In early 1960 many companies began commercializing Electronic Article Surveillance (EAS) or anti-theft systems that are based on a very simple RFID concept. These RFID tags that are still in use today have 1 bit of digital information. The bit of an unpaid (unscanned) item is originally set to “on”; and when a patron pays for that item, the bit is set to off by the cashier. A switched-off tag will not trigger the alarm system when the item leaves the store (i.e., passes through the interrogation zone, located at the exit gate.)

Those earlier RFID developments have paved the way for today’s booming deployment of RFIDs in industrial and commercial applications. The varieties of application-specific requirements have led to operation of RFID tags mostly in three main frequency bands today: the industrial (low-frequency), scientific (high-frequency), and medical (ISM—ultra-high-frequency) bands.

1.5 OPERATING FREQUENCIES

There are three main varieties of RFID tags in use today. They all operate at Industrial, Scientific, and Medical (ISM) band.

1.5.1 Low Frequency

In the early days of RFID, low-frequency (LF) tags were the most common. The LF tags operate at 125 kHz and 134.2 kHz. Because of the electromagnetic properties at LF frequencies, those tags can be read while attached to objects containing water, animal tissues, metal, wood, and liquids. They are only suitable for proximity applications, because they can be interrogated from a very short range of only a few centimeters.

They have the lowest data transfer rate among all the RFID frequencies and usually store a small amount of data. The LF tags have no or limited anti-collision capabilities, therefore, reading multiple tags simultaneously is almost impossible. The LF tag antennas are usually made of a copper coil with hundreds of turns wound around a ferrite core.

Because of these properties of LF tags, they are well-suited for specific applications such as access control, asset tracking, animal identification, automotive control, vehicle immobilizer, health-care, and various point-of-sale applications. In particular, LF tags have been intensively used for animal tracking since the early 1980s. Nowadays, the automotive industry is the largest user of LF tags. For example, in an automobile vehicle immobilizer system, an LF tag is embedded inside the ignition key. When that key is used to start the car, an RFID interrogator placed around the key slot reads the tag ID. The car can be started only if the correct ID can be read from the key.

1.5.2 High Frequency

The high-frequency (HF) tags operate at 13.56 MHz. Their operating principles are similar to LF tags they use near-field inductive coupling as source of power to communicate with the interrogator. HF tags have a better read range than LF tags and can be read from up to half a meter away. They have a better data transfer rate and larger memory size (up to 4 kbyte) compared to LF tags. The HF tags may have anti-collision capability that facilitates reading of multiple tags simultaneously in the interrogation zone. However, since the read range of many HF tags and interrogators is small, anti-collision features are usually not implemented to reduce the complexity and consequently its cost.

HF tag antennas are usually made of several turns of conductive materials such as copper, aluminum, or silver as a flat spiral. Therefore, HF tags are usually very thin and almost two-dimensional (as thick as paper). They can be made in different sizes, some only a couple of centimeters in diameter. Simple antenna design translates in a low-cost fabrication. HF tags can be easily read while attached to objects containing water, tissues, metal, wood, and liquids. Their performance, however, is affected by metal object...