**1. Introduction**

[16] F. Al-Shraideh, "Host Identity Protocol," International Conference on Networking, International Conference on Systems and International Conference on Mobile Com‐ munications and Learning Technologies, ICN/ICONS/MCL 2006., pp. 203, 23-29

[17] S. Deering and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification," Inter‐ net Society, RFC 2460, December 1998. Available from: *http://tools.ietf.org/html/rfc2460*

[18] "ISO/IEC 14443 Identification cards - Contactless integrated circuit(s) cards - Proxim‐

[19] "ISO/IEC 15693 Identification cards - Contactless integrated circuit(s) cards - Vicinity

[20] "ISO/IEC 18000 Information technology - Radio frequency identification for item

[21] Bose and R. Pal, "Auto-ID: managing anything, anywhere, anytime in the supply chain," Communications of the ACM, vol. 48, no. 8, pp. 100-106, August 2005.

[22] P. Nikander, T. Henderson, C. Vogt, and J. Arkko, "End-Host Mobility and Multi‐ homing with the Host Identity Protocol", Internet Society, RFC 5206, April 2008.

[23] D. Eastlake and P. Jones, "US Secure Hash Algorithm 1 (SHA1)," Internet Society, RFC 3174, September 2001. Available from: http://tools.ietf.org/html/rfc3174

[24] R. Rivest, "The MD5 Message-Digest Algorithm," Internet Society, RFC 1321, April

[25] B. Xu, Y. Liu, X. He, and Y. Tao, "On the Architecture and Address Mapping Mecha‐ nism of IoT," 2010 International Conference on Intelligent Systems and Knowledge

[26] Pappas, S. Hailes, and R. Giaffreda, "Mobile Host Location Tracking through DNS, " London Communications Symposium (LCS) and Photonics London, LCS 2002,

[27] T. Aura, "Cryptographically Generated Addresses (CGA)," Internet Society, RFC

[28] EM Microelectronics, "EM4100 / Read Only Contactless Identification Device," data

[29] EM Microelectronics, "EM4450/4550 / 1 KBit Read/Write Contactless Identification Device," data sheet, 2010. Available from: *http://www.datasheetarchive.com/*

[30] D. Johnson, C. Perkins, and J. Arkko, "Mobility Support in IPv6," Internet Society,

Available from: *http://www.ee.ucl.ac.uk/lcs/previous/LCS2002/lcs2002.html*

3972, March 2005. Available from: *http://tools.ietf.org/html/rfc3972*

RFC 3775, June 2004. Available from: *http://tools.ietf.org/html/rfc3775*

sheet, 2004. Available from *http://www.datasheetarchive.com/*

management." Available from: *http://www.iso.org/iso/home/store.htm*

ity cards." Available from: *http://wg8.de/sd1.html#14443*

cards." Available from: *http://wg8.de/sd1.html#15693*

Available from: *http://tools.ietf.org/html/rfc5206*

1992. Available from: http://tools.ietf.org/html/rfc1321

Engineering (ISKE), pp. 678-682, November 2010.

April 2006.

130 Radio Frequency Identification from System to Applications

The use and development of Radio Frequency Identification (RFID) systems has undergone substantial growth in the past decade in many new areas. Some of these areas include wire‐ less sensor systems, metamaterials and compact antennas [1-8]. However, much of this new growth has required more performance from traditional passive RFID systems. In particu‐ lar, the need for more compact antennas with performances comparable to much larger res‐ onant antennas is one such condition. To fulfill the requirements of compact antennas, researchers have developed various novel RFID antenna designs [2-4], including metamate‐ rial-based RFID antenna designs [1,5-8] to improve the performance of RFID systems. Using composite right/left-handed (CRLH) transmission line (TL) based metamaterials to show the unique property of zeroth-order resonance (ZOR) [9,10] is one such method to reduce the overall size of an antenna. More specifically, a ZOR-TL can be used to make an electrically small antenna to appear electrically large; which leads to improved matching and radiation properties. This is done by producing a zero phase constant at a non-zero frequency (i.e. the wavelength of the travelling wave becomes infinite) on the TL. This is a unique property which makes the resonance condition independent from the physical dimensions of the an‐ tenna or TL [11-13] so it can be used to design miniature antennas for passive UHF RFID applications. The resonance of such antennas at any operating frequency only depend on its CRLH characteristics to acquire ZOR at that frequency and less to do with the physical di‐ mensions of corresponding antenna.

properly cited.

© 2013 Mubeen Masud and D. Braaten; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is © 2013 Mubeen Masud and D. Braaten; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

This chapter will focus on the design of ZOR antennas for passive UHF RFID tags. First, a brief introduction and working principles of RFID systems is presented using Friis's trans‐ mission equation. Then, the characteristics of CRLH transmission lines will be discussed and its Bloch impedance will be derived to introduce the ZOR concept. Then coplanar-wave‐ guides (CPW) and its characteristics are presented. Then the design of a capacitive loaded CPW based ZOR antenna for passive UHF RFID tag is discussed. Finally, future work and conclusion about this chapter is presented.

A RFID system consists of a RFID reader and a RFID tag. An overview of a typical RFID system is shown in Fig. 1. RFID systems comprise of RFID tags or transponders which are fairly simple, small and inexpensive devices at one end and a reader which is relatively complex and a bigger device on the other end. Application Specific Integrated Circuits (ASICs) are attached to the tag antenna and are used for sensor applications, to harvest ener‐ gy, communicate and store information for later recovery. The reader emits an electromag‐ netic field which contains power and timing information for use by the passive RFID. If a RFID tag comes within the range (also known as the interrogation zone [1]) it receives the information which is fed to the ASIC and in response the ASIC switches its impedance states between a lower and higher value in a predetermined fashion as shown in Fig. 2. By chang‐ ing the impedance states the ASIC changes the radar cross-section (RCS) of the tag antenna thus changing the backscattered power. This backscattered power is collected at the reader and is used for tag identification and information. The maximum distance for which a read‐

Design of a Zeroth Order Resonator UHF RFID Passive Tag Antenna with Capacitive Loaded Coplanar…

http://dx.doi.org/10.5772/53284

133

RFID tags are usually classified into three categories: active tags, semi-passive tags and pas‐ sive tags [1]. An active tag has a dedicated power supply for operation on the tag. A semipassive tag has an integrated power supply attached to it and it only starts working when electromagnetic power transmitted by the reader is incident on the tag. This feature enhan‐ ces the maximum read range of the tag [1] because less power is required from the incoming incident field from the reader. A passive tag has no power source attached to it and it har‐ vests power for its operation from the incident electromagnetic field transmitted by the

Za

RFID Tag Antenna Impedance

Antenna RFID ASIC

A common method to describe the RFID wireless communication system is the following

*GrGt*λ<sup>2</sup>

*Pr* =*Pt*

Zc1 Zc2

(4*πR*)2 *<sup>q</sup>* (1)

er can successfully identify a tag is known as max read range.

Va

**Figure 2.** Thevenin equivalent circuit of RFID tag

Friis transmission equation [16]:

I

RFID Tag

reader.
