Author ORCID Identifier

Year of Publication


Degree Name

Master of Science in Mechanical Engineering (MSME)

Document Type

Master's Thesis




Mechanical Engineering

First Advisor

Dr. Johné M. Parker


Passive ultra-high frequency (UHF) radio frequency Identification (RFID) has emerged as a promising solution for many industrial applications. Passive UHF systems are relatively inexpensive to implement and monitor, as no line of sight is required for the communication. There are several advantages to using a passive RFID system. For example, no internal power source is required to activate the tags, and lower labor costs and efficient multitasking operations are expected in a long term scenario. However, due to factors such as tag-to-tag interference and inaccurate localization, RFID tags that are closely spaced together are difficult to detect and program accurately with unique identifiers. This thesis investigates two main ways to enable and improve multi-tag operations: physical tag placement and design of the near-field RFID reader antenna. First, several factors that affect the ability to encode a specific tag with unique information in the presence of other tags are investigated, such as reader power level, tag-to-antenna distance, tag-to-tag distance and tag orientation. A Full Factorial Design is carried out to study the effects of each of the factors and factor interactions. Results suggest a preliminary minimum tag-to-tag spacing which enables the maximum number of tagged items to be uniquely encoded without interference. In order to individually read each tag in a multi-tag form, an experimental device is built to enable controlled movement and positioning of the reader’s antenna to the location of each of the tags. The experimental device is also designed to test other mechanical means of isolating the tags, such as shielding and mechanical isolation of the tagged media. Furthermore, to test a second method of improving the efficacy of programming tags uniquely in a multi-tag environment, the reader’s antenna is redesigned to confine the electromagnetic field distribution to reduce the probability of activating non-targeted tags in the surrounding. Using the commercial software package ANSYS High Frequency Structural Solver (HFSS), the coupling interaction between the reader’s antenna and RFID tags was simulated to investigate the relative voltage induced in the target tag relative to each of the proximal tags. The new antenna is then fabricated and validated with the simulation results. With a better antenna design and ideals tag placement, the read operation of multiple tags can be improved and made more reliable. These findings can potentially expedite the process of field programming in item-level tagging and increase the throughput rate of unique tag encoding.

Digital Object Identifier (DOI)