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1、P1: JDW JWBS032-07JWBS032-KarmakarAugust 6, 201017:16Printer Name: Yet to Come CHAPTER 7 HANDHELD READER ANTENNA AT 5.8 GHz SUSHIM MUKUL ROY, ISAAC BALBIN Department of Electrical and Computer Systems Engineering, Monash University, Clayton, Victoria, Australia NEMAI CHANDRA KARMAKAR Department of E
2、lectrical and Computer Systems Engineering, Clayton, Victoria, Australia 7.1INTRODUCTION Similar to the handheld optical barcode reader, there is a signifi cant market seg- ment for the handheld readers. The examples include the wand for library database management system, apparel tagging and checki
3、ng of hanging tags, animal tracking, dispatch and inventory control at the manufacturing premises, courier services and deliveries, and so on. The existing systems work in LF and HF band around 132 kHz and 13.56 MHz, respectively, and the handheld readers use a loop antenna (magnetic dipole also cal
4、led wand as used by magicians) to read the tags. These antennas have omnidirectional patterns to cover maximum reading zone as possible. However, due to the magnetic coupling between the reader and the tag, the distance of the reader is very short, usually less than a few tens of centimeters. Figure
5、 7.1a shows the confi guration of a handheld reader used in the inventory check of books on a library book shelf. As can be seen, the RFID reader consists of a handheld loop antenna and an RFID reader (with battery pack, display, etc.), which are connected by an RF cable for data transmission and re
6、ception. The handheld antenna (also called wand) is carried by the hand of a person who reads the tags attached to the item. The scanning is done by hand sweeping the tagged items (books on a library book shelf) with the wand at a close proximity. These antennas are LF and HF magnetic loop antennas.
7、 Sometimes the antennas are covered with a plastic radome. The reader electronics with a battery pack is bulky with the RF transceiver Handbook of Smart Antennas for RFID Systems, Edited by Nemai Chandra Karmakar CopyrightC?2010 John Wiley (b) Intermec IP4 Portable RFID Reader (Courtesy: Reader imag
8、e suppliedbyIntermecTechnologiesAustraliaPtyLtd.);(c)proposed5.8-GHzintegratedplanar reader antenna mounted on the side of reader (baton); (d) inclined angle antenna mount with adjustable angles; (e) hat top antenna on handheld reader. P1: JDW JWBS032-07JWBS032-KarmakarAugust 6, 201017:16Printer Nam
9、e: Yet to Come INTRODUCTION175 electronics, a digital data control section, and a displayall are integrated in a single case. The reader is carried on the shoulder, with a strap connected to the reader like a bag or attached to a belt to be fi xed on a persons waist. The conventional system is bulky
10、 and needs separate parts like the wand, the cable assembly, and the reader electronicshence it is not convenient to carry and use. The current demand of the market is to improve the situation by pushing the operating frequency in S and C bands by exploiting the far-fi eld EM radiation. The objectiv
11、es are to achieve compact design, long reading range (exploiting the far-fi eld radiation), high reading speed, and provision to read multiple tags in a very fast sequence. To achieve the objective, the reader needs to cover as many tags as possible in its reading zone but with high-gain beams to le
12、verage the link budget. The objective can be fulfi lled by designing antenna arrays that are compact in design and moderately high gain. The wireless local area network (WLAN) uses antennas with difference patterns to cover as many terminals as possible in an offi ce. The approach in the design disc
13、ussed in this chapter has adopted the same principle of WLAN to gen- erate the difference patterns and/or wide-beam patterns. To fulfi ll the design goal, a comprehensive design exercise is performed in the chapter. Figure 7.1b shows an IP4TMRFID Reader from Intermec TechnologiesTMoperat- ing in UHF
14、 band. The reader operates as a complete standalone module. In a similar way, in the systems proposed in this chapter, all components will be integrated into a single module as shown in Figures 7.1ce. The antenna is a fully planar microstrip patch antenna array with a compact circular power divider
15、and antenna elements in a circular grid. Based on the operational need, the antenna can be designed to pro- duce sum (directional) patterns and difference patterns (omnidirectional) in order to maximize the reading distance and zone, respectively. With a switching electronics and control algorithm,
16、the antennas beam patterns can be controlled adaptively and switchedbetweenthetwomodesofoperationtomaximizethesignal-to-interference- plus-noise ratio and system capacity. As can be seen in the conceptual design of the integrated handheld RFID reader, the reader electronics can be designed as a baton and the planar antenna can be mounted on a side (Figure 7.1c) on the top of the baton with adjustable angles as an angle grinder (Figure 7.1d), as well as on a side of the baton as a conformal
