Design of a Novel Chipless RFID Tag with High Code Density

Abstract

For many years, optical barcode technology has been utilized in different situations to read, track, identify, and monitor numerous objects because of its low cost and reliability. However, this technology has been exposed due to its limitations, including the lack of security, line-of-sight (LoS), and short range. To overcome all the above-mentioned constraints, wireless radio frequency identification (RFID) technology is utilized for identification of the target items. Most of the RFID systems in the market have active tags which contain an active chip and a power source to energize them. These chipped-based tags are very expensive for item-level tagging. To solve these problems, chipless RFID tags are being which doesn‟t need any chip or power source. But there are many challenges in designing these tags, like high code density, code capacity and spectral efficiency. This thesis presents two designs, one is focused on increasing code capacity and code density of the CRFID tags and the other is focused on designing an application CRFID tag. The first design presents a unique geometry for encoding a large number of bits in a small form factor CRFID tag to overcome above mentioned constrains. The tag geometry consists of semi-octagonal copper strips, sequentially laid on a single side of an ultra-thin substrate. A unique and robust encoding mechanism for tag ID has also been proposed. The tag has been designed to work in the Ultra-Wide-Band (UWB) from 3.1-10.5 GHz. The overall size is compact bearing an area of 14.1 × 27.6 mm2. The proposed tag has a very high code density of 10.27 bits/cm2 and a spectral efficiency of 5.4 bits/GHz. The unique geometric configuration used allows for encoding up to 40-bits of data in the RCS signature of the proposed tag. This Chipless RFID tag is deemed fit for a wide range of modern identification scenarios and will prove to be a useful tool for RFID system designers. In the second design a chipless 10-digit touch event-based keypad sensor for detection and localization of human touch is presented. The proposed tag is capable of sensing human touch at 10 different locations. The tag contains ten circular rings each of the rings is assigned by a number with respect to its location on a keypad. The proposed tag detects touch event by the disappearance of particular resonance from it allocated band. The tag reader senses touch by continuously tracking the RCS response of the tag. As the touch event occurs, one of the ten resonances disappears, that‟s how the reader knows which of the resonator is touched. This tag has many advantages over other sensing technologies due to its low cost, low level of complexity and passive nature. These properties make it a potential candidate for controlled access and authorization applications for IoT.