Current Trends and Challenges in RFID 80 2. Minimum emitter area for matched transistors, otherwise there will be a degradation in the current gain (β); 3. Guard ring around the base to ensure that electrostatics charges will not influence the current flow in the neutral base; 4. Use of multiple collectors for lateral PNP transistors. A moderate match can be reached when the collectors are identical and out of the saturation condition; 5. The matched transistors should be close to each other in order to minimize the impact of the thermal gradient. 6. The matched transistors should be placed in gradients lines of minimum stress; 7. The transistor must be aligned with the wafer axis; 8. Place as many metal contacts as possible in the emitter (following the emitter geometry) to reduce the contact resistance and to distribute the current flow uniformly; 9. Use emitter degeneration. Lateral PNP transistors are often more benefited with emitter degeneration compared to the NPN vertical counterparts due to the Early voltage and the large emitter area. They are commonly used in current mirrors. The matching over integrated components reflects the overall performance of the entire circuit or system. Depending on the matching accuracy, the circuits may present: 1. Minimum: In the range of ± 1% (representing 6 to 7 bits of resolution). Used for general use components in an analog circuit, such as current mirrors and biasing circuits; 2. Moderate: In the range of ± 0.1% (representing 9 to 10 bits of resolution). Used in bandgap references, operational amplifiers and input stage of voltage comparators. This range is the most appropriate for analog designs. 3. Severe: In the range of ± 0.01% (representing 13 t0 14 bits of resolution). Used in high precision analog to digital converters (ADCs) and digital to analog converters (DACs). Analog designs that use capacitors ratio reach this range easer then those that using resistors ratios. Figure 26 shows an example of a PNP vertical bipolar transistor layout. Fig. 26. PNP vertical bipolar transistor example. 9. LVR measurements The example LVR was diffused in a 0.35μm standard CMOS process. It took an area of approximately 0.25 [mm 2 ]. Structural Design of a CMOS Voltage Regulator for an Implanted Device 81 Figure 27 depicts the testing structure utilized to measure the main LVR parameters. It is used a commercial operational amplifier (LM318) as a buffer to isolate the chip. The load current can be adjusted by potentiometer P 1 and the total load capacitance, considering the all parasitic, was measured as 30 [pF]. Before any LVR measure, the LM318 offset voltage was compensated through the procedure provided by the manufacturer. All the power supply lines are decoupled by 10 [μF] capacitors. Fig. 27. The test structure to measure the LVR parameters. Parameters Simulated Measured T NOM 37[ºC] 37[ºC] V IN 2.2[V] 2,218[V] I L ( NOM ) 0.5[mA] 0.5[mA] P D ( NOM ) 1.17[mW] 1.186[mW] V OUT 1[V] @ I L = 0.5mA 1.038[V] @ I L = 5[μA] 1.004[V]@ I L = 0.5[mA] I Q 30[μA] 39[μA] PSRR @ 10MH Z -42.6dB -38dB E FF related to V IN 42.8[%] 42.3[%] T SET @ 0,1% 14.87[μs] 18.6[μs] OTA dominant pole 130[H Z ] 126[H Z ] Table 6. Main LVR simulated and measured parameters. Current Trends and Challenges in RFID 82 Figure 28 shows the LVR response to a voltage step input and reveals a BIBO (bounded input – bounded output) system, in other words, the system is unconditionally stable and there is no need of any extra external component. Table 6 is a comparison between the simulated and measured parameters. Fig. 28. LVR step response indicating a BIBO system. The measured values show a good conformity with the simulated ones indicating proper design considerations. 10. Conclusions We are witnessing the great revolution that has been imposed since the manufacture of the first bipolar transistor in the late 50s of the twentieth century. Electronics solutions are going to microelectronics and microelectronics is evolving to nanoelectronics. All these developments bring with them the yearning of the human being to access more efficient equipment. So, in virtually all branches of activities we will find what is called "High- Tec". Medicine and its related sciences could not stay apart from this explosion of technology and intelligently sought the partnership with this powerful tool for circuit design. Some solutions point to implantable systems (which would reduce the use of invasive techniques) that can be taken up on an outpatient basis and connected into a means of communication for a distance evaluation by a health professional. The main objective of this chapter was the development of a voltage regulator for implantable applications. Some boundary conditions allow classic Figures of Merit, such as the temperature dependence, to be less severe, since the body temperature is kept constant. Another key issue was to search for solutions that avoid the presence of any external component. This is an essential boundary condition since the topology of classical LDO regulators depends on the presence of a capacitor (usually electrolytic and therefore too large for this application) connected in parallel with the load. Other regulators reported in the literature uses complex circuits or circuits that requires large silicon area. Structural Design of a CMOS Voltage Regulator for an Implanted Device 83 The circuit described is a compromise of additional power dissipation in the source follower stage and unconditional stability. Even with the additional dissipation, the total power of the regulator (about 1.2 [mW]) is within a safe limit. 11. References [1] Ahmadi, M.M. & Jullien, G.A., (2009). A Wireless Implantable Microsystem for Continuous Blood Glucose Monitoring. IEEE Trans. Biomedical Circuits and Systems, 3(3), pp.169-180. [2] Colomer-Farrarons J., Miribel-Catala P., Rodríguez I., S.J., (2009). CMOS front-end architecture for In-Vivo biomedical implantable devices. In Industrial Electronics, 2009. IECON ’09. 35th Annual Conference of IEEE . p. 4401 – 4408. [3] Dejhan, K. et al., (2004). A CMOS Voltage-Controlled Grounded Resistor Using a Single Power Supply,. In Communications and Information Technology, 2004. ISCIT, IEEE International Symposium on . pp. 124-127. [4] Ferreira, L.H.C. & Pimenta, T.C., (2006). A Weak Inversion Composite MOS Transistor for Ultra-Low-Voltage and Ultra-Low-Power Applications. In Proceedings of 13th International Conference Mixed Design Intregated Circuit Systems. pp. 10-12. [5] Gray, P.R. et al., (1993). Analysis and Design of Analog Integrated Circuits Fourth Edi., John Wiley and Sons. [6] Guennoun M., Zandi M., E K.K., (2008). On the use of Biometrics to Secure Wireless Biosensor Networks. In Information and Communication Tecnologies: From Theory to Applications, 2008. ICTTA 2008. pp. 1-5. [7] Hastings, A., (2001). The Art of Analog Layout, Prentice Hall. [8] Huang, W J., Liu, S H. & Lu, S I., (2006). A Capacitor-Free CMOS Low Dropout Regulator with Slew Rate Enhancement. In VLSI Design, Automation and Test, 2006 International Symposium on . pp. 1-4. [9] Huang, W J., Liu, S H. & Lu, S I., (2006). CMOS Low Dropout Regulator with Single Miller Capacitor. Electronics Letters, 42(4), pp.216-217. [10] Koushaeian, L. & Skafidas, S., (2010). A 65nm CMOS low-power, low-voltage bandgap reference with using self-biased composite cascode opamp. In Low-Power Electronics and Design (ISLPED), 2010 ACM/IEEE International Symposium on. pp. 95-98. [11] Kugelstadt, T., (1999). Fundamental Theory of PMOS Low-Dropout Voltage Regulators. Texas Instruments Incorporated. Application Note SLVA068, pp.1-5. [12] Landt, J., (2005). The History of RFID. Potentials, IEEE, 24(4), pp.8-11. [13] Lazzi, G., (2005). Thermal Effects of Bioimplants. Engineering in Medicine and Biology Magazine, IEEE, 24(5), pp.75-81. [14] Mackowiak, P.A., Wasserman, S.S. & Levine, M.M., (1992). A Critical Appraisal of 98.6°F, the Upper Limit of the Normal Body Temperature, and Other Legacies of Carl Reinhold August Wunderlich. The Journal of American Medical Association, 268(12), pp.1578-1580. [15] Mandal, P. & Visvanathan, V., (1997). Self Biased High Performance A Folded Cascode CMOS Op-Amp. In VLSI Design, 1997. Proceedings, Tenth International Conference on. pp. 429-434. [16] Miyazaki, M., (2003). The Future of e-Health – Wired or not Wired. Business Briefing: Hospital Engineering & Facilities Management , pp.1-5. Current Trends and Challenges in RFID 84 [17] Osepchuk, J.M. and P.R.C., (2001). Safety Standards for Exposure to RF Electromagnetic Fields. IEEE Microwave Magazine, 2(2), pp.57-69. [18] Patrick, G.D. & McAndrew, C.C., (2003). Understanding MOSFET Mismatch for Analog Design. IEEE Journal of Solid-State Circuits, 38(3), pp.450-456. [19] Puers, R., (2005). Implantable Sensor Systems. In DISens Symposium Book. pp. 1-14. [20] Ramos, F.G.R., (2007). Uma Referência de Tensão Programável Para Aplicações em Gerenciamento de Potência . Master Tesis at Universidade Federal de Itajubá, 2007. [21] Rincon-Mora, G.A., (2000). Active multiplier in Miller-compensated circuits. IEEE J. Solid-State Circuits , 35, pp.26-32. [22] Rincon-Mora, G.A. & Allen, P., (1998). A low-voltage, low quiescent current, low drop- out regulator. IEEE J. Solid-State Circuits, 33, pp.36-44. [23] Rincon-Mora, G. & Allen, P.E., (1997). Study and Design of Low Drop-Out Regulators. School of Electrical and Computer Engineering – Georgia. [24] Rogers, E., (1999). Stability Analysis of Low-Dropout Linear Regulators with a PMOS Pass Element. Texas Instruments Incorporated. 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A CMOS Bandgap Voltage Reference. IEEE journal of Solid-State Circuits, 14(3), pp.655-657. [31] Vaillantcourt, P., Djemouai A., Harvey J. F., Sawan, M., (1997). EM radiation behaviour uponbiological tissues in a radio-frequency power transfer link for a cortical visual implant. In Proc. IEEE Int. Conf. Engineering in Medicine and Biology. pp. 2499-2502. [32] Zheng, C. & Ma, D., (2010). Design of Monolithic Low Dropout Regulator for Wireless Powered Brain Cortical Implants Using a Line Ripple Rejection Technique. IEEE Transactions On Circuits And Systems - II: Express Briefs , 57(9), pp.686-690. Part 2 Antennas/Tags 5 RFID Technology: Perspectives and Technical Considerations of Microstrip Antennas for Multi-band RFID Reader Operation Ahmed Toaha Mobashsher 1 , Mohammad Tariqul Islam 1 and Norbahiah Misran 2 1 Institute of Space Science (ANGKASA), Universiti Kebangsaan Malaysia 2 Dept. of Electrical, Electronic and Systems Engineering Universiti Kebangsaan Malaysia Malaysia 1. Introduction This chapter presents a comprehensive review of RFID technology concerning the antennas and propagation for multi-band operation. The technical considerations of antenna parameters are also discussed in details in order to provide a complete realization of the parameters in pragmatic approach to the antenna designing process, which primarily includes scattering parameters and radiation characteristics. The antenna literature is also critically overviewed to identify the possible solutions of the multi-band microstrip antennas to utilize in multi-band RFID reader operation. In the literature dual-band antennas are principally discussed since they are ideal to realize and describe multi-band antenna mechanism. However, it has been seen that these techniques can be combined to enhance multi-band antennas with wider bandwidths. Last but not least, the high gain dual- band antennas and limitations have been described and it is realized that the conventional feeding technique might limit the performance of multi-band antennas to only one frequency. 2. Radio frequency identification The idea of early radio frequency identification (RFID) system was invented by Scottish physicist Sir Robert Alexander Watson-Watt in 1935. With the supervision of Watson-Watt, the British government developed the first active identify friend or foe (IFF) system. This prototype of RFID concept was modified in 1950s and 60s by using radio frequency (RF) energy for commercialization purpose. The first US patent in this field was published on January 23, 1973 for the invention of an active RFID tag with rewritable memory by M. W. Cardullo (Cardullo 1973). That same year, C. Walton received another RFID patent for a passive transponder used to unlock a door without a key. In the recent days, the low power ultra high frequency (UHF) RFID system research has gained a lot of importance after some of the biggest retailers in the world, e.g., Albertsons, Metro, Target, Tesco, Wal-Mart and the Current Trends and Challenges in RFID 88 US Department of Defense, have said they plan to use electronic product code (EPC) technology to track goods in their supply chain (Mitra 2008). RFID is an emerging technology for the identification of objects and/or personnel. RFID is recognized as one of the technologies capable of realizing a complete ubiquitous computing network due to its strong benefits and advantages over traditional means of identification such as the optical bar code systems. Comparing with barcode, RFID has some advantages of rapid identifying, flexible method and high intelligent degree (Wang et al. 2007; Xiao et al. 2008). Furthermore, it can function under a variety of environmental conditions (Intermec Technologies Corporation 2006). It has recently found a tremendous demand due to emerging as well as already existing applications requiring more and more automatic identification techniques that facilitate management, increase security levels, enhance access control and tracking, and reduce labor force. A brief listing of RFID applications that find use on a daily basis is:  Warehouse Management Systems  Retail Inventory Management  Toll Roads  Automatic Payment Transactions  High Value Asset Tracking and Management  Public Transportation  Automotive Industry  Livestock Ranching  Healthcare and Hospitals  Pharmaceutical Management Systems  Military  Marine Terminal Operation  Manufacturing  Anti-counterfeit 2.1 RFID system Basically RFID is a contact-free non-line-of-sight type identification technology using radio frequency consisting of a RFID transponder (tag), a RFID interrogator (reader) with an antenna and data processing unit (host computer). In case of the handheld RFID reader, the reader itself contains the feature of data processing unit. The typical block diagram of RFID system is shown in Fig. 1. Fig. 1. Block diagram of RFID system The interrogation signal coming from the reader antenna must have enough power to activate the transponder microchip by energizing the tag antenna, perform data processing and transmit back the data stored in the chip up to the required reading range (typically 0.3– [...]... As shown in Fig 4, several frequency bands have been assigned to RFID applications: 125/1 34 KHz, 13.56 MHz, 860-960 MHz, 2 .45 0 (2 .40 0–2 .48 3) GHz and 5.800 (5.725–5.875) GHz Several issues are involved in choosing a frequency of operation (Dobkin 2007) Fig 5 Inductive coupling or near field detection of RFID reader 92 Current Trends and Challenges in RFID The most fundamental, as indicated in the diagram,... number and possibly other information as well In simple RFID systems, the reader’s pulse of energy functioned as an on-off switch; in more sophisticated systems, the reader’s RF signal can contain commands to the tag, instructions to read or write memory that the tag contains, and even passwords (Garfinkel & Holtzman 2005) RFID readers are usually on, continually transmitting radio energy and awaiting... by many common materials in buildings and the environment, particularly those containing water The degree of absorption due to water increases gradually with increasing frequency Tags immersed in water-containing materials (i.e injected into or swallowed by animals or people) must use very low frequencies to minimize absorption: this is a typical 125 KHz application For locating large objects or people... Hernandez & Robertson 1995) 106 Current Trends and Challenges in RFID Loading the radiating edge with an inset (Nakano & Vichien 1989; Palit et al 1998) or a spur-line (Hernandez & Robertson 1995; Hernandez & Robertson 1993; Vaello & Hernandez 1998) (“notch loading”) is an alterative way to introduce a dual-frequency behavior that creates the same effect as the microstrip-loading effect, with the advantage... frequencies In practice, the TM200 and the TM300 modes cannot be used Indeed, owing to 100 Current Trends and Challenges in RFID the behavior of the radiating currents, the TM200 pattern has a broadside null, and the TM300 pattern has grating lobes The simplest way to operate at dual frequencies is to use the first resonance of the two orthogonal dimensions of the rectangular patch, i.e., the TM100 and the... microstrip antenna with a single feed for orthogonal dual-band operation and its and (b) VSWR plots (Chen & Wong 1996) Fig 12 Aperture coupled RMSA with an inclined slot An interesting feature of these antennas is their capability of simultaneous matching of the input impedance at the two frequencies with a single feed structure (denoted by “singlepoint” in Fig 11) This may be obtained with a probe-fed... ratio of the major axis to the minor axis; in other words, AR  major axis OA  minor axis OB ( 14) where   1   1 1 1 2 2  2 4 2 2 OA   Ex  Ey  Ex4  Ey  2Ex Ey cos(2  )    2  2 (15) and 1 1 2  2 4 2 2 OB   Ex  Ey  Ex4  Ey  2 Ex Ey cos(2  ) 2    2  The tilt angle  of the ellipse is given by 2 (16) 98 Current Trends and Challenges in RFID   2  2 Ex Ey  1 cos(... the ground plane 4. 3 .4 Slot antenna technique Another kind of reactive loading can be introduced by etching slots on the patch The slot loading allows for a strong modification of the resonant mode of a rectangular patch, particularly when the slots are oriented to cut the current lines of the unperturbed mode In particular, as shown in (Wang & Lo 19 84) , the simultaneous use of slots and short-circuit... receiver  94 Current Trends and Challenges in RFID In the following sections, some of the antenna parameters are described that necessary to fully characterize an antenna and determine whether an antenna is optimized for a certain application 3.1 Impedance bandwidth, reflection coefficient, VSWR & return loss Fig 8 Transmission line model Impedance bandwidth indicates the bandwidth for which the antenna... is 96 Current Trends and Challenges in RFID directed to a specific, known location According to the IEEE Standard Definitions of Terms for Antennas, an antenna radiation pattern (or antenna pattern) is defined as: “a mathematical function or a graphical representation of the radiation properties of the antenna as a function of space coordinates In most cases, the radiation pattern is determined in the . Wired. Business Briefing: Hospital Engineering & Facilities Management , pp.1-5. Current Trends and Challenges in RFID 84 [17] Osepchuk, J.M. and P.R.C., (2001). Safety Standards for. detection of RFID reader Current Trends and Challenges in RFID 92 The most fundamental, as indicated in the diagram, is whether inductive or radiative coupling will be employed. The distinction. materials in buildings and the environment, particularly those containing water. The degree of absorption due to water increases gradually with increasing frequency. Tags immersed in water-containing