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Precise estimation of object position and orientation using RF tags is an emerging application of RFID technology. In this work, we present a novel wireless two-dimensional position and orientation estimation and tracking technique that illustrates the concept of sensor fusion —using multiple, disparate sensor measurements to synthesize a single, superior estimate of position and orientation. The technique is implemented using a 5.8 GHz RFID system that consists of three readers and a customized tag equipped with a 3-axis accelerometer, 3-axis gyroscope and 3-axis magnetometer. Received signal strengths and packet-to-packet phase differences at the reader are used to measure radial tag positions and radial tag velocities, and backscattered data packets provide measurements of the tag’s linear accelerations, angular velocities and orientations. A hybrid inertial microwave reflectometry (HIMR) algorithm is used to produce motion-capture grade estimates of tag position and orientation; in experiments, a two-dimensional position accuracy of less than 13 mm was achieved. The HIMR algorithm is designed using physics-based modeling equations, modifications are proposed to accommodate temporary link loss, and observability analyses clarify the foundations of the estimator design method.

Hybrid inertial microwave reflectometry (HIMR) is one of the most promising technologies for achieving the elusive, ultimate goal of wireless localization, i.e., motion-capture grade position tracking at long-range distances. In this paper, we introduce and analyze Kalman filter-based real-time position estimators for HIMR systems. Results from measured data show that the new approach results in a 5 mm RMS tracking error at a range of several meters—a 25% improvement with enhanced robustness over existing position estimators. Moreover, this performance level is shown to be achievable using only RF signals, without inertial data, thereby potentially simplifying RFID-based motion capture system design in many cases. The technique is scalable to ranges of tens- and hundreds-of-meters.

Localization for visually impaired people in dynamically changing environments with unexpected hazards and obstacles is a current need. Many techniques have been discussed in the literature with respect to location-based services and techniques used for the positioning of devices. Time difference of arrival (TDOA), time of arrival (TOA) and received signal strength (RSS) have been widely used for the positioning but narrow band signals such as Bluetooth cannot efficiently utilize TDOA or TOA. Received signal strength indicator (RSSI) to measure RSS, has been found to be more reliable. RSSI measurement estimations depend heavily on the environmental interference. RSSI measurement estimations of Bluetooth systems can be improved either by improving the existing methodologies used to implement them or by using fusion techniques that employ Kalman filters to combine more than one RSSI method to improve the results significantly. This paper focuses on improving the existing methodology of measuring RSSI by proposing a new method using trilateration for localization of Bluetooth devices for visually impaired people. To validate the new method, class 2 Bluetooth devices (Blue Giga WT-12) were used with an evaluation board. The software required was developed in National Instruments LabView. The PCB was designed and manufactured as well. Experiments were then conducted, and surface plots of Bluetooth modules were obtained to show the signal interference and other environmental effects. Lastly, the results were discussed, and relevant conclusions were drawn.

Precise object position and orientation estimation using RF tags is an emerging application of RFID technology. In this work, we present a novel wireless two-dimensional position and orientation estimation and tracking technique that illustrates the concept of sensor fusion – using multiple, disparate sensor measurements to synthesize a single, superior estimation of position and orientation. The technique is implemented using 5.8 GHz RFID system that consists of three RFID readers and a customized motion capture tag equipped with 9- axis inertial and compass sensors. The microwave reader extracts 9- axis inertial and compass data: 3-axis accelerometry, 3-axis gyrometry, and 3-axis magnetometry from the backscattered packet. The HIMR algorithm then fuses inertial, compass data and the RF signature of the backscattered signal to produce a motion-capture grade estimate of position and orientation. A positional estimation accuracy of 1–2 cm was achieved in the narrowband experiments conducted using 5.8 GHz RFID system operating on multiple frequencies.

Accurately characterizing the wireless small-scale fading channel has been a challenging task in the wireless communication era due to the surrounding environment. Therefore, this paper introduces a new technique to experimentally characterize the small-scale fading taking under consideration real environmental conditions. By conducting a two dimensional measurement while the mobile receiver is moving; a more accurate channel will be achieved. Two-dimensional measurement refers to collecting data from the receiver along the x and y direction. The two-dimensional measurement data contain far more information than a one-dimensional data collected. In order to represent the small-scale channel along with the real environmental conditions, new approaches are necessary to configure the two-dimensional system and to analyze the 2D data. The new approach this paper introduces for the characterization is that the measurements are conducted on a receiver while it is moving in a two dimensional manner, under different scenarios, Line-of-sight, Non-line-of-sight, and Two-wave-Diffuse Power. The experiment was conducted in a 7 meters long by 4 meters wide room, wherein the distance between the transmitter antenna and receiver is about 3 meters. Those scenarios represent different real-time conditions where obstacles differ from one scenario to another. For example, the line of sight scenario assumes there a clear line of sight between transmitter and receiver, Non line of sight assumes many obstacles between the transmitter and receiver, i.e. walls, cabinets, etc. and Two Wave Diffuse Power assumes a metallic reflector surrounding the receiver. The experiment showed more accurate results when compared to the one dimensional measurement that has been done in the past where receiver is moving in one direction and also receiver being fixed where a constructive and destructive interference is not captured. The two dimensional measurement technique, i.e. capturing data while receiver moving in both x and y directions, provided essential information regarding the constructive and destructive interference patterns caused by the interaction between the receiver while moving and the obstacles surrounding the receiver.

This paper proposes a new fine-scale (millimeter level) radio localization and tracking scheme—Hybrid Inertial Microwave Reflectometry—for radio frequency identification and other wireless systems. The scheme combines the backscattered radio frequency signal properties, such as received signal strength and received signal phase, along with reflected inertial data from a tag-mounted accelerometer sensor. Experimental results yield a mean error of 2 mm in ranging accuracy, with a 90% confidence interval of $\pm$ 1 mm, while tracking a tag moving at a maximum speed of 1.4 m/s.

Antenna detuning can be used for a variety of sensing applications. In this paper, the performance of an E-patch and a conventional patch antenna was evaluated in the presence of dielectric materials. The gain penalty and the reflection coefficient of both the antennas were simulated and measured using a vector network analyzer. The performance of the E-patch antenna was evaluated to be much better than a normal patch antenna over each dielectric material. This analysis is useful for environmental monitoring, rescue, and surveillance applications.

Object localization is one of the most important applications of RFID technology. In this paper, we demonstrate how fine-scale orientation can be estimated from a multi-antenna backscatter tag. Three basic orientation changes — tag roll, pitch and yaw — were considered, where roll and pitch maneuvers were successfully identified from the direction of phase rotation. Moreover, an inclination of 5° in roll and pitch maneuvers was successfully identified by measuring the phase difference with 15% and 8% error respectively. The analysis can be extended to any amount of inclination.

This paper presents a broadband, RF backscatter-based sensing method to identify the presence of payment terminal tampering, particularly using small, unwanted electronics such as payment skimmers in close proximity to a 5.8 GHz RFID tag. The broadband nature of this methodology makes it resilient to false alarms from interfering RF signals. Consistent detection of a conductive object is achieved by tracking long term changes in both magnitude and phase of the backscattered signal. In laboratory measurements, the presence of thin metal wires was determined for distances up to two wavelengths from the tag.

The paper proposes an Agent System for multi faceted distributed generation setup with green power generators identifying role and requirements of each agent. The Object Model, treating various agents as Entity/Object is proposed showing their interaction/interfacing. Each entity has been elaborated with its attributes. In addition, the services expected from each agent are highlighted. The Use Case Model is proposed showing assigned role of each agent. Each use case has been elaborated with its purpose, data handling, stimuli and responses. A lay out of the sub-systems of each of the proposed main agents has also been included. Subsequently the State Machine Model is proposed showing behavior of system in real time scenarios. Finally the Event Loop Model is appended along with sensor/actuator control process.

In this paper, we present a 5.8 GHz RFID tag equipped with a high gain, low power reflection amplifier based on a tunnel diode. Experimental results show that the realized prototype achieves gains above 40 dB and requires only 29 μW of biasing power. The tag detects very low RF signals (< −90 dBm) and provides read ranges up to 2 km. Long communication ranges and Manchester encoding are achieved by biasing on and off the tunnel diode.

Radio frequency identification is a pervasive technology used for many different purposes. This paper presents a unique technique to evaluate tag's loads impedance without modifying its electronics. In this in-situ technique, no external measuring equipment such as vector network analyzer was directly connected with the tag. The complex back scattered signal together with simulated tag antenna's impedance and gain were used to extract its load impedance. The evaluated load impedance showed unified effect of the tag electronics and board parasitics.

Localization and tracking (L&T) are some of the most important applications of radio frequency identification (RFID) technology. One method of achieving this is by approximating the position of an object from the measured backscattered signal parameters and backscattered data. A comprehensive analysis of the backscattered signal parameters, such as received signal amplitude and phase, is necessary to establish their effect on the accuracy of L&T. In this context, this paper investigates the probability density functions (PDFs) of the received signal amplitude and phase for RFID systems. It was observed that both PDFs converge to Gaussian distributions in high signal-to-noise ratio scenarios. Moreover, the Cramer Rao Lower Bound (CRLB), which serves as an established reference for unbiased estimation, is also derived for the estimated received signal amplitude and phase difference. It was noticed that the CRLBs are inversely proportional to the number of observations taken for the parameter estimation. Finally, it is pertinent to mention that if multiple types of sensed information are fused to perform L&T, it results in millimeter-level accuracy. For RFID, one such technique which employs multiple sensed parameters for L&T is Hybrid Inertial Microwave Reflectometry (HIMR). This paper also presents a simulation and experimental analysis of HIMR. HIMR-based RFID tracking scheme results in tracking accuracy in the range of 1–10 mm.

This paper discusses how a low-powered RFID tag or sensor mote's backscatter modulation scheme - limited in ways that conventional digital wireless systems are not - may be adapted to the peculiar non-white noise properties of a backscatter receiver's radio frequency electronic chain to maximize detection. The analysis and results in this paper enable longer-range operation of today's passive, or semi-passive RFID tags as well as future backscatter sensor links that operate in higher frequency bands.

Radio Frequency Identification (RFID) tags are gaining popularity in sensing applications. Common implementations rely on backscattering digitally encoded sensor data from an RFID tag to a reader. This paper discusses a unique capability of RFID technology to detect objects in a tag's near vicinity by observing trends in the magnitude and phase of backscattered signal, irrespective of the information encoded in the data. Computational results and measurements are presented, and demonstrate how to improve sensitivity for object detection near a tag.

A novel miniaturized printed circular loop antenna with perimeter of nearly one wavelength is designed for operation with a radio-frequency identification (RFID) tag at 5.8 GHz. RFID tags and RFID-enabled sensors which operate at this frequency offer many benefits over traditional UHF and LF tags, such as smaller footprints and increased bandwidth. The loop is broken into conducting segments that alternate on either side of a substrate for capacitive loading needed to maintain a constant current and generate a near omni-directional radiation pattern. The performance of the loop antenna is measured in-situ with the tag and the reader configured as a microwave backscatter radio communication system at 5.8 GHz. An overview of the RFID tag design is presented along with measured backscattered pattern.

This paper presents an improvement of the read range, radar cross section (RCS) and reliability of radio frequency identification (RFID) tags using multiple antennas. Measurements were performed using custom built, semi-passive RFID tags with co-planar segmented-loop antennas. Results show an increased read range as compared to RFID tag with single segmented-loop antenna.

The paper proposes an agent system for distributed generation setup identifying role and requirements of each genetic algorithms, due to their applicability for optimization solutions of nonlinear and stochastic scenarios, can find place in development of agents for distributed control. Advantages and special features of genetic algorithms far optimization are discussed, identifying some input and output variables. Requirement of compensator as an agent/sub-agent is also proposed. The state machine model/event loop model is proposed showing behaviour of system in real time scenarios. To facilitate understanding, object model of the agent system has also been suggested, correlation with state/event loop model where possible