Delay line based passive radio frequency identification tags

This work describes the concept, design, fabrication, and characterization of delay-based radio frequency identification (RFID) tags and RFID-based sensor tags, representing a novel RFID technology. The presented delay-based RFID concept is based on the LC-delay-line and transmission-delay-line based approaches. The proposed concept allows the realization of RFIDs and RFID-based sensor tags at any allowed radio frequency, with the limitation of realizing delay elements capable of producing required delays. The RFID configurations presented in this work are for operation at 915 MHz. Simulations are used to design and optimize components and devices that constitute the tags, and to integrate them to realize tags of different configuration. A set of fabrication processes has been developed for the realization of the tag. Characterization and field testing of these tags show that delay-based RFID approach can be used to make passive tags at ultra high frequency (UHF) and other allowed frequencies. Delay-based tags have the advantages of time domain operation, and the feasibility of complying with FCC regulations. However, size, need of isolators and circulator, and design constraints in producing higher number of bits are some of the concerns that need to be further addressed. In summary, this dissertation work presents a viable alternative RFID approach based on the delay line concept. The results obtained show great promise for further development and optimization of this approach for a wide range of commercial applications

Frequency Multiplexed Radio Frequency Identification

A radio frequency identification (RFID) system for frequency multiplexing includes, in an exemplary embodiment, an RFID interrogator configured for generating an RFID signal, wherein a channel frequency of the RFID signal changes over time within an operating bandwidth; and one or more electromagnetic transmissive elements each extending between a first end thereof and a second end thereof, each of the electromagnetic transmissive elements electrically coupled with the RFID interrogator at the first end thereof, each of the electromagnetic transmissive elements comprising a frequency dependent load at the second end thereof and configured for transmitting the RFID signal from the RFID interrogator to the frequency dependent load, wherein the frequency dependent load presents different electromagnetic characteristics to the RFID signal transmitted to the frequency dependent load depending on the channel frequency of the RFID signal. Other embodiments include a method for frequency multiplexing including similar components

Optimal sensor arrangements in Angle of Arrival (AoA) and range based localization with linear sensor arrays

This paper investigates the linear separation requirements for Angle-of-Arrival (AoA) and range sensors, in order to achieve the optimal performance in estimating the position of a target from multiple and typically noisy sensor measurements. We analyse the sensor-target geometry in terms of the Cramer–Rao inequality and the corresponding Fisher information matrix, in order to characterize localization performance with respect to the linear spatial distribution of sensors. Here in this paper, we consider both fixed and adjustable linear sensor arrays

An 8x1 Wideband Antenna Phased Array

In this project, we are trying to detect the direction of arrival of incoming radiation in the far-field region. To achieve this, we implemented a very flexible and low cost wideband 8x1 phased array antenna receiver system that performs digital beamforming. We designed and built ten aperture coupled patch antennas, radio-frequency (RF) front ends and intermediate-frequency (IF) stage blocks for each channel. Finally, we stored the data in the first-in-first-out (FIFO) memory placed on a Vertex6 FPGA on which we synthesized a microblaze microcontroller that uses SPI to control programmable RF devices and transfers data to the computer for further processing. Super-resolution direction of arrival and model order detection algorithms were implemented to perform the digital beamforming

Real-time localization using received signal strength

Locating and tracking assets in an indoor environment is a fundamental requirement for several applications which include for instance network enabled manufacturing. However, translating time of flight-based GPS technique for indoor solutions has proven very costly and inaccurate primarily due to the need for high resolution clocks and the non-availability of reliable line of sight condition between the transmitter and receiver. In this dissertation, localization and tracking of wireless devices using radio signal strength (RSS) measurements in an indoor environment is undertaken. This dissertation is presented in the form of five papers. The first two papers deal with localization and placement of receivers using a range-based method where the Friis transmission equation is used to relate the variation of the power with radial distance separation between the transmitter and receiver. The third paper introduces the cross correlation based localization methodology. Additionally, this paper also presents localization of passive RFID tags operating at 13.56MHz frequency or less by measuring the cross-correlation in multipath noise from the backscattered signals. The fourth paper extends the cross-correlation based localization algorithm to wireless devices operating at 2.4GHz by exploiting shadow fading cross-correlation. The final paper explores the placement of receivers in the target environment to ensure certain level of localization accuracy under cross-correlation based method. The effectiveness of our localization methodology is demonstrated experimentally by using IEEE 802.15.4 radios operating in fading noise rich environment such as an indoor mall and in a laboratory facility of Missouri University of Science and Technology. Analytical performance guarantees are also included for these methods in the dissertation --Abstract, page iv