P0-14 Inline SAW RFID Tag Using Time Position and Phase Encoding

Surface acoustic wave (SAW) radio-frequency identification (RFID) tags are soon expected to be produced in very high volumes. The size and cost of a SAW RFID tag will be key parameters for many applications. Therefore, it is of primary importance to reduce the chip size. In this work, we describe the design principles of a 2.4-GHz SAW RFID tag that is significantly smaller than earlier reported tags. We also present simulated and experimental results. The coded signal should arrive at the reader with a certain delay (typically about 1 mus), i.e., after the reception of environmental echoes. If the tag uses a bidirectional interdigital transducer (IDT), space for the initial delay is needed on both sides of the IDT. In this work, we replace the bidirectional IDT by a unidirectional one. This halves the space required by the initial delay because all the code reflectors must now be placed on the same side of the IDT. We reduce tag size even further by using a Z-path geometry in which the same space in x-direction is used for both the initial delay and the code reflectors. Chip length is thus determined only by the space required by the code reflectors.

SAW-RFID enabled temperature sensor

Radio Frequency IDentification (RFID) technology successfully integrates radio transmitter and receiver, small size memory space and control circuitry to remotely store and retrieve data via wireless RF transceiver. As low-cost RFID tag can be massively manufactured by semiconductor industry, new applications associated with RFID technology have emerged rapidly such as inventory tracking, book storage and management, and airport baggage handling. Generally an RFID system is composed of many RFID tags (or tagged objects), at least one RFID reader, and one backend application system with database. An RFID tag gains its operation energy from query signals that are radio waves transmitted by RFID reader. Once a tag responds the query with its stored information to RFID reader, usually a unique identity number or string, the RFID system can recognize the tag carrier and perform required business logic operation. As RFID technique is widely used in supply chain management, the corresponding RFID application systems are expected to process and manage large amount of tagged objects at a predefined period of time regularly. Therefore, for large-scaled RFID applications, tag reading throughput is very critical since it will affect the total data processing time. To measure tag reading throughput of a RFID system, two performance criteria are usually adopted: tag reading delay and reader energy consumption [5]. As RFID reader and tag always communicate over a shared wireless channel, it is very easy to have signal collisions during a normal tag identification process when multiple tags exist in reader’s interrogation area. Signal collision results in query or data retransmission and eventually increases communication overhead and time delay of tag identification. Hence, an efficient tag collision arbitration mechanism is very important and critical for RFID systems to achieve effective performance. Existing RFID tag identification schemes can be classified into aloha-based solutions [3, 10, 12-13, 16, 21, 23-24] and tree-based solutions [1, 2, 4, 6-9, 14-15, 17-20, 22]. In aloha-based schemes, a reader estimates the number of tags in its interrogation area and broadcasts the total number of timeslots to each tag. Then each RFID tag randomly selects its own timeslot to transmit its ID without knowing which timeslots have been selected by other tags. By distributing tag responses to distinct timeslots instead of getting all tag responses at the same time, aloha-based schemes effectively reduce the probability of signal collision. However, aloha-based schemes have tag starvation problem in which certain tags may not

Reflected signals from multiple wireless surface acoustic wave (SAW) sensors are generally asynchronous, which causes difficulty in simultaneous identification of multiple SAW sensor tags. This paper proposes a matrix method for multiple SAW sensor tags identification based on orthogonal frequency code (OFC). The characteristics of ideal overlapped signals from multiple OFC SAW tags are analyzed. According to the analysis, the amplitudes and the phases of the overlapped signals with the same center frequency from the identical reflector positions of different tags can be measured. A matrix equation for the relationship between the measurable values and the amplitudes delay of signals from each tag is presented. Tag identification is accomplished by solving this matrix equation. According to the characteristics of this matrix equation, the maximum number of simultaneous identifiable tags is roughly equal to the square of the number of selectable matching frequencies of reflectors. A set of simultaneous identifiable tags are selected. All tags randomly chosen from this tag set can be identified correctly by the simulation test. This result verifies that the matrix method for multiple OFC SAW sensor tags identification is feasible in theory.

The first radio identification systems appeared already during World War II for military applications, namely, for identification of planes. However, it is only now that the technical conditions are right for a wide use of radio frequency identification (RFID). The two key issues for the RFID technology are the number of different codes that can be ‘written’ on a tag and the possibility to store, transfer, and communicate information. Due to the ongoing miniaturization of semiconductor integrated devices, mass production of such devices at a low cost has become possible. More specifically, microand nanometer lithographic technology allows for the fabrication of very small tags (with a chip size on the order of 1 mm and smaller) operating at the GHz-range where sufficiently wide frequency bands are available. These industrial, scientific, and medical (ISM) frequency bands can be used without licensing with a limited radiated power. The wide frequency bands finally allow for a practically infinite number of different codes to be written and read at microsecond time intervals. As to the second key issue, the omnipresent internet, intranet, and similar communication networks enable the processing of databases and developing of smart systems that use the information automatically read from RFID tags. It is interesting to point out that the dramatic development of mobile phones (that only combine a transmitter and a receiver, both used in radio communications for a century by now) was based exactly on the same two reasons: first, the development of technology allowing the use of high frequencies, wide frequency bands and, finally a large number of subscribers and, second, computer databases with high-speed data links enabling fast communication. The type of RFID tag introduced in this chapter, the surface acoustic wave (SAW) tag, is in many aspects similar to RF SAW filters, that are widely used in mobile phones. SAW tags and SAW filters use the same technology.

In order to identify more surface acoustic wave (SAW) sensor tags simultaneously, the characteristics of superposed signals reflected from multiple orthogonal frequency coded (OFC) SAW tags are analyzed. Although these signals arriving at a reader are asynchronous, the different central frequency signals still keep orthogonal in an appropriate time window range as long as all tags are within a certain distance. The amplitudes and phases of the superposed signals with same central frequency from the identical reflector positions of different sensor tags can be measured. The matrix relational expression between the measurable values and the amplitudes, delay of signals from each tag is found out. Then, tags identification is converted into solving this equation. The relation between the maximum number of simultaneous identifiable tags and the number of optional central frequencies of reflectors is obtained with the assumption that all reflected signals arrive at a reader synchronically. The simultaneous identifiable OFC SAW tags set is selected with the above assumption. It is explained that the selected tags set can also be identified simultaneously on condition that reflected signals arrive at a reader asynchronously. The above theoretical analysis is verified by iterative method in MATLAB software.

A radio-frequency identification (RFID) system has been considered as one of the most promising systems for information technology (IT) asset management because of its well-developed level of technology, worldwide standards and its lower price than other wireless protocols such as WiFi, WiMAX, and Bluetooth. However, RFID systems for IT asset management in business-to-business (B2B) environments are still limited by several constraints such as readable range, sensor capability, and battery problems inherent in existing RFID technologies. In particular, only few research works deal with asset management in a real office environment. This paper proposes a new way of managing IT assets using surface acoustic wave (SAW)-based RFID technology to solve these problems. To show its effectiveness and feasibility, the proposed approach analyzes RFID tag performance based on an electromagnetic test and measures the readability of SAW-based RFID in an office environment. Experimental results show that one of the most hopeful candidates for managing B2B IT assets is the SAW-based RFID system because of its batteryless passive RFID characteristic, relatively long readable range, its potential and inherent sensor capability, and its expandability compared to other RFID systems. Furthermore, the proposed approach systematically analyzes where to attach RFID tags on IT asset devices considering electromagnetic performance based on ID- and sensor-detecting capabilities, which suggests the most appropriate tag position on the device.

An overview of the results of twenty years of research on solving the problem of anticollision protection of radio frequency identification tags on surface acoustic waves is given. A comparison of different methods of anticollision protection is carried out. The results of solving this problem for an unlimited number of tags are presented.

Tunable surface acoustic wave (SAW) devices have attracted considerable interests due to its applications in emerging fields, such as secured wireless communication, adaptive signal processing, and smart sensing systems. We report a dual-input-voltage-controlled tunable SAW built on glass, which uses a ZnO-based dual-layer structure consisting of a piezoelectric Ni-doped ZnO (NZO) and semiconducting Mg-doped ZnO (MZO). The interdigital (IDT) electrodes are buried in the piezoelectric NZO layer to form the delay line for SAW propagation, while the semiconductor MZO layer serves as the channel of a thin film transistor (TFT) to modulate the conductivity. Results show the interface between MZO channel and SiO2 gate dielectric layer of the TFT significantly impacts on SAW tuning performances due to Zn diffusion from MZO into SiO2. The TFT-SAW device using an ultra-thin MgO layer as interface modification enables SAW frequency tuning of 0.53% under solely Vgs control with 0–12 V. The required voltage range is significantly reduced compared regular MZO-NZO TFT-SAW counterpart (Δf/fc ∼ 0.25%; Vgs −30 to −14 V) without interface modification. With additional control of Vds, the SAW frequency tunability is further expanded from 0.46% to 0.63%. This dual-input voltage-controlled frequency tuning device on glass is promising for low-voltage, low-cost portable smart sensors and voltage-controlled reconfigurable radio-frequency identification tags.

The paper focuses on the environmental burden created by Radio Frequency Identification (RFID) tags in the Slovak Republic (SR). In order to determine the burden there, a model example was created to calculate electronic waste produced by households in the SR by placing RFID tags into municipal waste. The paper presents a legislative regulatory approach towards the environmental impacts from using RFID tags in the SR, as well as an analysis of the environmental burden of using RFID tags throughout the world. The core of the paper is focused on the research conducted in order to calculate the environmental burden of a model household in the SR, where the number of used RFID tags per year was observed; then, the volume of e-waste produced by households of the Slovak Republic per year was determined. In the conclusion, we provide the results of the research presented and discuss including our own proposal for solving the problems connected with the environmental burden of RFID technology.

In the last decade, many articles have been pub­lished that demonstrate the susceptibility of cryptographic devices against implementation attacks. Usually, such devices draw their energy from a contact-based power supply. This power-supply connection is often exploited to extract the secret key by applying fault-injection methods and power-analysis attacks. In this article, we present implementation attacks on Radio Frequency Identification (RFID) tags which are usually powered contactlessly by an electromagnetic field. We describe a contact-based measurement setup that allows both injection of faults and measuring of the power consumption of passive RFID tags. Furthermore, we demonstrate the applicability of our setup by providing practical results of attacks on commercially available HF and UHF RFID tags. The results have led us to the conclusion that RFID tags are as susceptible to such attacks as contact-based powered devices. Appropriate countermeasures are needed to thwart these attacks.

Academicians and industry professionals have demonstrated the use of Radio Frequency Identification (RFID) Tags in construction applications in the past few years. Recently building information modelling (BIM) technology is emerging as the industry standard in the architecture, engineering and construction (AEC) sector. This paper combines the two technologies to monitor the movement of RFID tags in a BIM environment. Real-time monitoring of RFID tags in a building information model is an improvement over other methods of tracking construction workers, equipment and materials on the jobsite. Strategies for combining the two technologies are explored. This method of monitoring can be used to improve the safety and productivity of construction workers on a construction jobsite. This technique of monitoring RFID tags can also be used to track equipment and construction materials on a job-site. Autodesk Revit BIM software environment was used for tracking RFID tags. The paper includes discussion about the choice of RFID tags available for this method of tracking.

We present a self-consistent model calculation to study the influence of a radio-frequency surface acoustic wave (SAW) on the dynamic processes of photo-generated free carriers, excitons and trions in a 2D MoS2 flake with an odd number of layers. We found that the concentrations of excitons and trions decreased, while the lifetime of the free carriers increased when an external SAW field was applied. We attribute this phenomenon to the spatial separation of the electrons and holes, which are confined by a SAW-induced periodic type-II band-edge. We further studied the effect of the modulations on the spatiotemporal distributions of free carriers and excited quasiparticles by varying the amplitude and wavelength of the SAW field. We finally calculated the photoluminescent properties of the MoS2 flake under modulation of the SAW field and compared our results with those of recent experiments.

In this paper, we focus on configuring a low cost RFID (Radio Frequency IDentification) system with less RFID readers and low density RFID tag textiles for stable and accurate self-localization for an omni-directional mobile robot. An RFID system using multiple RFID readers and high density RFID tags has already been applied to an indoor mobile robot self-localization. However, the system production cost is relatively high. To reduce the production cost of the system while maintaining the self-localization performance, we redesign two new RFID systems configured with 20 RFID readers and 5 RFID readers enlarging the size of an RFID reader antenna. Particularly, a new likelihood function of the tag detection with the redesigned large size RFID reader antenna is proposed for Monte Carlo Localization (MCL). Furthermore, we come up with a novel arrangement of RFID tags installed in a hexagon pattern. The new arrangement of ID tags enables both low cost ID tag installation and high performance of self-localization. We examine the performances of robot self-localization with less RFID readers and lower density RFID tags installed on the floor based on MCL(Monte Carlo localization). The simulation demonstrates the validity of our proposed configuration of the RFID based self-localization.

In this paper, an innovative low cost elderly balance rehabilitation platform using ultra high frequency (UHF) radio frequency identification (RFID) tag array is proposed. Due to liquid filling effect onto an object with traditional passive tags, the tag impedance loading is altered. Received Signal Strength Indicator (RSSI) variation from tag response could be used for postural balance sensing. In order to realize multiple elderly balance rehabilitation, switched beam pattern control of UHF RFID reader is developed and a postural balance system in between ±20° from left/right to front/rear is demonstrated.