Passive Ultra High Frequency RFID Research Articles

Passive Ultra High Frequency RFID sensor with reference tag for crack detection of aluminum alloy structure

It can be ensured safe and reliable operation of a metallic structure by monitoring the positions which are easy to crack. Because the channel changes with the environment, a tag sensor in the ultra high frequency (UHF) is vulnerable to interference. This paper aims to investigate the reliability of passive RFID sensor systems with a reference tag for crack detection of aluminum alloy structures when the condition of reading distance and surrounding environment changes. The impedance and gain of tags are simulated, which provides theoretical basis for experimental analysis. With an increase of crack depth, the impedance of the sensor tag shifts to the low frequency direction, and the reference tag changes slightly. When dual tags are placed orthogonally, the gain of the sensor tag changes greatly, which means that it is more sensitive to crack depth. The backscatter power of the sensor tag shows a decline trend, and the power of the reference tag remains unchanged. The sensor features a linear response with the variation of crack depth. The sensitivity of crack characterization is better when dual tags are placed orthogonally.

Design of Nested H slot Passive UHF RFID Tag

RFID is a short distance communication system which comprises of a RFID tag, a RFID reader and a personal computer with desired software that can maintain the related information. These RFID tags can be of active or passive types. This paper focuses on design, simulation and fabrication of passive ultra-high frequency RFID tag (microchip and an antenna) which resonates at the frequency 866 MHz in the Industrial Scientific Medical Band. The nested H-slot inverted-F microstrip antenna structure is used for the design of passive RFID tag. It examines the specific tag geometry and its characteristics to optimize the PIFA antenna and in turn RFID tag’s performance.

Design of new power generating circuit for passive UHF RFID tag

In this paper, we propose a new power generating circuit for passive ultra high frequency (UHF) RFID tag. The proposed power generating circuit consists of a RF limiter, a high power efficiency and high sensitivity full wave radio frequency (RF) wave rectifier and a low-power regulator with NMOS diodes work like a DC-limiter. The design method proposed in this study use one low drop out (LDO) regulator to provide tow output stable supply voltages vdd1 of value 1V for the digital section supply, and vdd2 of value 0.5V for the analog front-end section power supply. The proposed power generating circuit is optimized in terms of power consumption of RFID tag system to have a high operating range under conditions of 50 Ohm antenna, -24 dBm input RF power, 900MHz and 1 M DC, with low power dissipation and 29.15% large power conversion efficiency. The power generating circuit was designed, simulated and layouted in Cadence using TSMC 180 nm technology. The final design occupies approximately 0.25mm<sup>2</sup>.

Experimental Performance Evaluation of Passive UHF RFID Tags in Electromagnetically Critical Supply Chains

Radio Frequency Identification is going to play a veryimportant role as auto-identification solution for manyapplication scenarios, where item-level tagging and highperformance are crucial. In such a context, the use of passive Ultra High Frequency (UHF) tags is strongly suggested but, unfortunately, general-purpose commercial tags could not meet all the requirements in presence of critical operating conditions, including the presence of metals and liquids, the misalignment between tag and reader antennas, and the need of multiple reading of tags. In this paper, the main features that a UHF tag should own to work properly in the whole supply chain are presented. A tag, named below Enhanced tag, satisfying all theindividuated requirements has been also realized and validated in a controlled test environment simulating the pharmaceutical supply chain. Tests have been focused on the above-mentioned critical conditions. The performance of the Enhanced tag, in terms of successful read rate, has been compared with that of some commercial Far Field and Near Field UHF tags. The experimental results are impressive and clearly demonstrate that ad hoc Far Field UHF tags are able to effectively solve many of the performance degradation problems affecting generalpurpose tags. Finally, the proposed tag has been also tested in extreme conditions, applying it directly on Tetra Pak packages containing liquid, with interesting results in terms of platformtolerant features.

New design of RF rectifier for passive UHF RFID transponders

A novel diode-connected MOS transistor for ultra-high-frequency (UHF) micro-power rectifiers was presented, and a high efficiency N-stage charge pump voltage rectifier based on this new diode-connected MOS transistor was designed and implemented. The new diode-connected MOS transistor and the rectifier are designed and fabricated in SMIC 0.18-μm 2P3M CMOS embedded EEPROM process. The structure design of the new diode achieved 315mV turn-on voltage, and 415nA reverse saturation leakage current. Compared with traditional rectifier, the rectifier using the presented diode-connected MOS has higher power conversion efficiency (PCE), higher output voltage and smaller ripple coefficient. When the RF input is a 900-MHz sinusoid signal with the amplitude ranging from 0.8 to 1.8V, PCEs of the charge pump rectifier with only 3-stage are more than 30%, and the maximum output voltage is 5.02V, and its ripple coefficients are less than 1%.

Virtual Private Networks [Guest Editorial

Handheld radio frequency identification reader units become increasingly important with the adoption of passive ultra-high frequency RFID systems in supply chain, warehouse, and retail store management. Important requirements for the handheld reader unit are ergonomic size and weight, sufficient battery life, and suitable read range for the desired applications. In addition, usability of the reader unit in terms of reading directions and orientations of tags has to be taken into account. This article presents a performance comparison of compact reader antennas for a handheld UHF RFID reader unit. The reader antennas presented in this study are designed to be affixed either inside the casing of the reader unit or into an external reader antenna module. The presented antenna designs have been optimized with finite element method modeling. The resonance frequency and bandwidth characteristics are analyzed using modeled and measured results. Read range measurement results with the antenna designs affixed to the handheld reader are presented and analyzed to verify the practical performance. All the antenna designs presented in this article are applicable to a handheld RFID reader unit.