This paper presents a passive cavity type Ultra High Frequency (UHF) Radio Frequency Identification (RFID) tag antenna having the longest read-range, and compares it with existing long-range UHF RFID tag antenna. The study also demonstrates mathematically and experimentally that our proposed longest-range UHF RFID cavity type tag antenna has a longer read-range than existing passive tag antennas. Our tag antenna was designed with 140 × 60 × 10 mm 3 size, and reached 26 m measured read-range and 36.3 m mathematically calculated read-range. This UHF tag antenna can be applied to metal and non-metal objects. By adding a further sensing capability, it can have a great benefit for the Internet of Things (IoT) and wireless sensor networks (WSN).Keywords: RFID tag antenna; long range RFID tag; cavity antenna; RFID metal tag; RFID sensors; Internet of things; wireless sensor network; RFID-based IoT; RFID based WSN; smart RFID IntroductionRFID uses electromagnetic fields to identify automatically and to track tags attached on any object. It's used for applications like animal tagging, asset tracking, electronic passports, smartcards, store security, logistic and etc. [1]. The tags store object information electronically. There are passive and active RFID tags. There are LF (low frequency), HF (high frequency) and UHF RFID tag antennas [2] based on the frequency bands. Passive tags have no battery and collect energy from nearby RFID readers by interrogating radio waves, whereas active tags have a battery and can be detected over 100 m.According to applications and design technology, there are many articles published about UHF active tags. The read-range of the active tag is above 1 km with tag sensitivity under −80 dBm in 5.8 GHz and 433MHz bands [3][4][5]. On the other hand, a general passive UHF tags have about 10-20 m read-range based on the sensitivity of the tag chip and the types of antennas.Our passive UHF RFID tags have longer read-range than other designs. There will be benefits of tag with longer read-range since it can be incorporate with the sensing and communicating capabilities.Article [6] describes many novel applications of RFID sensors, novel antennas for metallic surface, 3D antennas, multi-band antennas, omnidirectional, and directional antennas in UHF, HF, or microwaves (MW) frequency bands. The sizes and read-range are also compared with different RFID Chips, and the longest read-range in the article is 14.6 m for the metal mountable antenna. Our passive UHF RFID tag had 26 m read-range using Higgs 4 RFID Chip manufactured by Alien Tech. Higgs 4 has sensitivity of −20.5 dBm.The more sensitivity of RFID tag chip has longer read-range with the same antenna. Different manufactures and different RFID chips have different level of sensitivities. The chip with the better sensitivity allows the tag to be read from farther range. If tag with longer read-range is integrated with sensors, it can have the following advantages: wireless powered identification in non-line-of-sight way, wide coverage and mobility RF...

No abstract

This paper presents the design of a 920 MHz Ultra High Frequency (UHF) band radio frequency identification (RFID) conductive fabric tag antenna. The DC (Direct Current) resistance and impedance of the conductive fabric are measured by a DC multimeter and by a network analyzer at a UHF frequency band. The conductivities of the fabrics are calculated with their measured DC resistance and impedance values, respectively. The conductivities of the fabric are inserted into the CST simulation program to simulate the fabric tag antenna designs, and the results of the tag designs with two conductivities are compared. Two fabric UHF RFID tag antennas with a T-Matching structure, one with the name-tag size of 80 × 40 mm, and another with 40 × 23 are simulated and measured the characteristics of tag antennas. The simulated and measured results are compared by reflection coefficient S11, radar cross-section and reading range. The reading range of the 80 × 40 mm fabric tag antenna is about 4 m and 0.5 m for the 40 × 23 size tag. These fabric tags can be easily applied to an entrance control system as they can be attached to other fabrics and clothes.

In this paper, we describe a long-range convex cavity-type passive ultra-high-frequency (UHF) radio frequency identification (RFID) tag to use on various metal and non-metal surfaces, for IoT sensor energy harvesting. The tag antenna is built on the 3D printed cavity structure with polylactic acid (PLA) plastic and painted with the conductive ink on the 1 mm protruding area (convex) of inner surface and the side-walls of the cavity structure to form a cavity structure. The tag is designed to operate in the UHF band (840–960 MHz). This long-range cavity tag antenna (CTA) works at both 920 MHz and 915 MHz UHF RFID frequencies. It provides a linear polarized (LP) frontal reading range of 35 m and side reading range above 15 m when mounted on either metal or non-metal objects. We describe the antenna characteristics, structure, modeling, simulation, and experimental results. A mathematical reading range also was calculated and compared with experimental data.