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The most important variables to consider in the design of antennas for RFED applications and effective communications are low cost, low profile, and reduced size. The dipole antenna, often known as a dipole aerial, is the most basic and widely used type of antenna. Among other antennas, this is one of the most straightforward antenna layouts. It may be achieved by applying a sinusoidal voltage differential between two thin metallic rods. The dipole antenna is a particularly important type of RF antenna that is frequently used for radio transmission and reception. For many types of antennas, this antenna can be employed as a radiating or driving element. This Dipole antenna may be used in the radio frequency spectrum sections HF, VHF and UHF. The major advantage of a dipole antenna is that it can serve as both a broadcast transmitter and receiver. So, to obtain the most crucial factors, we'll design an antenna in COMSOL Multi Physics and display the results as Radiation patterns.

The vehicle localization, which aims to identify a vehicle and then position the vehicle with a high precision, can be used to facilitate various applications and services in vehicular networks. Unfortunately, conventional localization systems, e.g., global positioning system (GPS), hardly meet the accuracy requirements especially in certain specific scenarios, such as tunnels. At the same time, Ultrahigh frequency (UHF) radio frequency identification (RFID) has become an efficient booster for internet of things (IoT) due to the desirable advantages, such as low cost, battery-free, and unique identification. In this paper, based on the UHF-RFID, we propose a novel real-time vehicle localization scheme in GPS-Less Environments. Considering the practical implementation of multiple RFID reader antennas on a vehicle is constrained, we adopt single antenna multi-frequency ranging scheme, in which the integer ambiguity problem is solved by the maximum-likelihood estimation (MLE)-based robust Chinese remainder theorem (CRT). With the reconstructed distances between the tags and the reader, the coordinates of the vehicle then can be calculated with the Levenberg-Marquardt (LM) algorithm. Furthermore, the computational complexities of the algorithms and the time consumption of the proposed scheme are analyzed. The experimental results demonstrate that the proposed scheme can track vehicle's location with error lower than 27 cm at the probability of 90%.

This communication presents a design of a dual-band circularly polarized antenna with structure reuse for 1U CubeSat applications. It is a challenging to design an antenna with the limited space of a CubeSat platform. To improve the space utilization, an antenna is designed inspired by the concept of structure reuse. A meshed-like-structure is designed, which works as the radiator of a microstrip antenna at UHF band. However, it works as a partial reflective sheet for a Fabry-Perot resonator cavity antenna at C band. Therefore, a microstrip patch antenna and a Fabry-Perot resonator cavity antenna share only single aperture. A shaped ground is used to decrease the resonance at the lower band. Then, the aperture of the antenna is only 0.3λ0 × 0.3λ0, which makes it easy to integrate with a 1U CubeSat. The measurement reveals that the antenna has a common bandwidth of (|S11| < -10 dB, AR < 3 dB) 1% and 1.4%, an isolation higher than 35 dB and 20 dB, a peak gain of 5.82 dBic and 13.75 dBic at UHF and C band, respectively. The frequency ratio of these two bands reaches 6.4. The above properties make the proposed antenna suitable for a CubeSat system.

In this paper, MUSE, an algorithm enabled by backscattering tag-to-tag network (BTTN) is presented to accomplish simultaneous 2-D localization of large-scale (10m 10m) massive (20~50) passive UHF RFIDs. In BTTNs, the most intractable problem is the high-frequency loss of range measurements. In a particular case of 30 tags to be located with maximum communication range being 3m, the rate is nearly up to 85.75%. In the proposed framework, we utilize relevant knowledge in the theory of graphs to obtain underlying subsets in which tags can communicate with each other and then assemble them stage by stage to achieve overall localization. Theoretical analysis shows that multistage assembly imparts extraordinary characteristics to MUSE: Assembling rectifies fragment maps given some condition, and in later stages prevents errors flowing down into the next stage. Experimental analysis shows that the condition is easy to satisfy. Furthermore, an analytical expression for the Cramr-Rao lower bound is also derived as a benchmark to evaluate the localization performance. Extensive simulations demonstrate that MUSE outperforms existing algorithms for simultaneous localization.

Owing to the shorter wavelength in the millimeter-wave (mmWave) spectrum, miniaturized antennas can receive power with a higher efficiency than UHF bands, promising sustainable mmWave-powered Internet of Things (IoT) devices. Nevertheless, the performance of a mmWave power receiver has not been compared, numerically or experimentally, to its sub-6 GHz counterpart. In this paper, the performance of mmWave-powered receivers is evaluated based on a novel wearable textile-based higher-order mode microstrip antenna, showing the benefits of wireless power transmission (WPT). Firstly, a broadband antenna is proposed maintaining a stable wearable measured bandwidth from 24.9 to 31.1 GHz, over three-fold improvement compared to a conventional patch. The proposed antenna has a measured 8.2 dBi co-polarized gain with the highest thickness-normalized efficiency of a wearable antenna. When evaluated for compact power receivers, the measured path gain shows that WPT at 26 GHz outperforms 2.4 GHz by 11 dB. A rectenna array based on the proposed antenna is then evaluated analytically showing the potential for up to 6.3x higher power reception compared to a UHF patch, based on the proposed antenna's gain and an empirical path-loss model. Both use cases demonstrate that mmWave-powered rectennas are suitable for area-constrained and large-area wearable IoT applications.

A compact tag antenna, which has a geometrical dimension of 31.5 mm × 31.5 mm × 3.2 mm, is constructed using a stacked PILA for metal-mountable applications in the UHF RFID passband. The new antenna is formed by inserting a shorted patch into a PILA structure to create a double-layered inverted antenna, which can be viewed as a cascade of two parallel resonant tanks. An increase in electric field intensity in the antenna structure has brought in sufficient capacitance for reducing the tag resonant frequency effectively to the useful UHF RFID passband. Due to the increase in the antenna reactance, conjugate impedance matching can be easily achieved between the antenna and the microchip. Fine-tuning schemes such as stubs and slits are also incorporated with the proposed tag antenna for adjusting the operating frequency to an exact precision. Measurements show that the proposed tag antenna can achieve a read distance of 7.25 m at an EIRP power of 4 W. The resonance of the proposed tag antenna is found to be very stable and it is insensitive to changes in the backing metal platform.

Two compact UHF tag antennas, which consists of a square ring loaded with two distributed inductors, are proposed for on-metal applications. Miniaturization of the antenna footprint is realized through the incorporation of two distributed inductors. It will be shown that the required inductances are much dependent on their locations on the ring resonator due to the variation of the current intensity. Due to the high-inductive nature of the distributed inductor, the antenna resistance of the ring resonator can be significantly enhanced so that it can achieve a conjugate impedance match with the microchip. A detailed analysis has been performed to understand the resonance characteristics, and transmission line models have been constructed for designing the tag antennas. Due to the significant improvement in the impedance matching, the proposed miniature tag antennas can achieve a far read distance of greater than 9 m on metal when they are tested with an effective isotropic radiated power (EIRP) of 4 W. Important to mention is that the tag resonant frequencies of the proposed tag antennas are stable and they are not affected much by the backing metallic objects.

As the Ultra High Frequency (UHF) passive Radio Frequency IDentification (RFID) technology becomes increasingly deployed, it faces an array of new security attacks. In this paper, we consider a type of attack in which a malicious RFID reader could arbitrarily access the tags, e.g., retrieve or modify IDs or other data in the memory, via standard commands. To deal with this type of attack, we propose a physical-layer tag protection framework, namely Arbitrator2.0, that involves two operating mode, i.e., one is to passively listen on RF channels and identify unauthorized readers, the other is working as normal reader to access tag information but resilient to one-antenna eavesdropper. Our solution does not need to modify RFID tags or the underlying communication standards. In this study, we have implemented a prototype Arbitrator2.0 over the Universal Software Radio Peripheral (USRP) platform, and conducted extensive experiments to evaluate its performance. The results show that Arbitrator2.0 can effectively diminish the unauthorized access attacks and prevent eavesdropping.

In this letter, a circularly polarized (CP) metal-tolerant tag antenna with long reading distance (RD) is proposed for the ultra-high frequency (UHF) radio-frequency identification (RFID) systems. In order to realize CP radiation and high gain, a cross slot is etched on top patch to provide two orthogonal polarizations, whereas the meandered strip on central copper layer is used to obtain 90o phase difference between adjacent ports. An equivalent circuit model (ECM) is established to better understand the operating mechanism and impedance characteristic. A prototype mounted on a 200 mm 200 mm metal plate has been manufactured and measured to verify the design, and shows an impedance bandwidth of 8 MHz (918-926 MHz) and axial ratio bandwidth of 1.3 MHz (921.6-922.9 MHz). Also, a maximum gain of 2 dBi at 922 MHz and a maximum RD of about 22.4 m have been demonstrated.

For the first time, the ionic polymer metal composite (IPMC) actuator is integrated with a RFID (Radio-Frequency Identification) tag antenna for achieving frequency reconfiguration in the UHF (Ultra-High-Frequency) band. Here, the IPMC movable flap serves as an actuator that can effectively tune the tag resonant frequency. By applying a 2-layer crenellated structure and employing a surface patterned electrode for restraining back relaxation, the deflection of the IPMC actuator can be significantly improved. The IPMC actuator can move in two directions, enabling two-degree frequency tuning. Numerical and experimental data confirm that the tip displacement of the IPMC actuator can be enhanced up to 266% with the use of the 2-layer crenellated structure. The IPMC actuator allows the resonant frequency of the tag antenna to be tuned back by as much as 35 MHz, after deviating due to placing on an unintended object. UHF RFID application is also performed using a portable commercial RFID reader. Good frequency reconfiguration and broad tuning range, along with far read distances, have been achieved with our tunable UHF RFID tag antenna.

Ultra High Frequency Radio Frequency Identification (UHF RFID)-based sensing technology with antenna-integrated sensor tags offers a cost-effective solution for Internet of Things (IoT) applications. A multi-dimensional differential measurement technique for eliminating the effect of measurement setup, such as unknown mutual distance and orientation between the read/write device (RWD) and sensor tags, and line-of-sight obstruction, on acquiring information from multiple sensor tags simultaneously is proposed. The concept is based on 1) using a channel hopping mechanism to acquire multi-dimensional datasets and 2) conducting a dissimilarity analysis between offline and online datasets to extract sensor information. The differential measurement, which is activated by the channel hopping mechanism, mitigates the impact of the measurement setup, making the pattern of the multi-dimensional datasets tightly relate to the sensing state. A sensor tag for measuring the water filling level of polyvinyl chloride (PVC) pipes is designed and fabricated. Experiments show that the proposed method can accurately acquire information from three sensor tags simultaneously under different measurement setups. The performances using datasets of different dimensions are compared. Results reveal that using low-dimensional datasets can still be capable of getting accurate information from the sensor tags, implying that the acquisition time can be reduced.

A denture implanted UHF RFID tag antenna is proposed. The limitation on antenna size means that a low-loss and compact antenna including matching circuit is necessary to increase the tracking distance. To reduce the loss brought by reflection, a partially exposed folded dipole antenna with gamma matching is utilized. The denture implanted RFID tag is fabricated by using materials utilized in the exact denture such as metal wire and resin. Furthermore, the RFID operation properties of the denture implanted tag are evaluated by changing the parameters of antenna structure. Based on the measurement result, the new proposed structure reduce the reflection loss from the mismatch between RFID chip and small antenna, which provides enough energy for communication. Also, this proposed antenna structure provides a brand new idea for designing antenna in medium.

The monitoring of magnetic fields is extremely important in many industrial environments, e.g., power grids. Despite of its importance, the existing monitoring methods either are large in size, require high power consumptions and manual observation, or although integrated in small wireless devices, need the use of batteries, increasing maintenance costs. This paper proposes an intermittent magnetic field monitoring system based on passive ultra-high frequency (UHF) radio frequency identification (RFID) technology. A magnetic field magnitude sensor has been integrated into a micro-controller unit (MCU) based tag, and the standard RFID communication protocol ISO/IEC 18000-6 Type C has been partially modified to allow faster sensed data transfer, especially for multiple tag situations rarely considered in the open literature. Static or 50 Hz magnetic field sensing accuracy lower than 3experimentally measured with reasonable tag charging times and read distances, making possible for example to monitor magnetic fields on more than 10 locations simultaneously with a 60 s of updating time with a tag read range of 3 m.

A compact printed-circuit leaky-wave antenna is designed to synthesize frequency-scanned monopulse patterns in the UHF RFID band from 902 MHz to 928 MHz. A high- permittivity ceramic substrate is used to maximize the angular scanning range in such a narrow band. Two operating modes, i.e. narrow-field and wide-field modes, can be chosen by properly selecting the frequency channels and antenna ports. This allows to adapt to different fields of view for a better performance in terms of angular estimation accuracy under low Signal-to-Noise condition, as demonstrated with a fabricated prototype.