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Rectangular Patch Slot Antennas RPSA are getting becoming more likable and popular for practice in wireless implementations such as RFID applications especially in the UHF band thanks to its low-profile structure. This kind of antenna is able to deliver large communication distances but this antenna coverage is very weak which is part of the main drawbacks of these antennas. In this paper, Rectangular Patch Slot Antenna RPSA with different slots has been designed and simulated to be suitable for RFID applications. Circular polarized CP antenna that has been designed to use feed structure with vertical ground encircling a radiating component. The feeding method to feed this antenna is coaxial probe. The paper will concentration on both substrate materials Roger 4350 and FR4 Glass-Epoxy material to model and simulate the designs. The other factor of the design is the patch antenna will cut at the four truncated corners to enhance the antenna gain which will affect considerably the operating frequency. This paper aims to show and find the best feed point area that has an exceptional antenna return loss (S11) and high gain. S11 describe the power reflected from the antenna, which is known as the reflection coefficient S11 must be ≤ -10dB. The design and simulation results of RPSA has been done by high frequency simulation system (HFSS 13.0).

A dual-band UHF/industrial, scientific and medical (ISM) compact rectenna with wideband UHF matching (855–935 MHz) covering all, EU, U.S., and Chinese UHF radio frequency identification (RFID), standards is presented. The proposed design consists of a compact single-port, dual-band antenna, a three-port dual-branch matching network, and two voltage doubler rectifiers implemented with Schottky diodes and terminated with a common 10 $\text{k}\Omega $ load. For each band, the measured RF-to-dc efficiency is around 60% for a −5 dBm unmodulated signal. The wideband behavior of the rectenna supports harvesting of multitone signals. The use of a six-tone signal increases the maximum RF-to-dc efficiency of the dual-band rectifier, from approximately 60% for a single-tone UHF signal (890 MHz) to 80% for a six-tone signal for a received RF power of −5 dBm in both cases. A signal generator is used to generate a six-tone signal of equally weighted and equally spaced (10 MHz separation) monochromatic tones, with a total bandwidth of 50 MHz. The measurement results demonstrate that the dc voltages rectified from the two separate RF signals are effectively superimposed on the load, providing a clear advantage compared to single-band rectennas. The single-layer, compact design with a size of $80\times45$ mm2, with a high RF-to-dc efficiency, is an excellent candidate for wirelessly powered RFID tags.

Indoor localization via radio-frequency identification (RFID) carries critical importance due to its high accuracy and low hardware requirement. The positions of reader antennas can affect the positioning accuracy and coverage in RFID network. In this letter, we present a novel RFID network planning (RNP) approach to optimize the deployment of reader antennas for accurate 3-D location. First, the 3-D antenna radiation mode of a passive UHF RFID system is set up. Then, the received signal strength (RSS) and path loss characteristics (PLC) are analyzed and a restricted genetic algorithm (RGA) is developed to obtain the optimal solution of the RNP via maximizing the total reward function with constraints. Finally, the convolutional neural network (CNN) and weighted $K$ -nearest neighbor (WKNN) algorithms are respectively used to verify the localization effect. For comparison, the Cramer-Rao lower bound (CRLB) is also derived. The experimental results show that the proposed approach can improve the positioning accuracy as well as the coverage, and enhance the anti-noise capability of the location system.

The time difference of arrival (TDOA) localization method has been widely applied in partial discharge (PD) localization in substations based on an ultra-high-frequency (UHF) antenna array. However, TDOA errors obtained from different UHF antennas can result in poor localization accuracy. In this paper, a novel nonlinear transform localization algorithm based on regularization for PD in substations is proposed. First, to avoid the problem of difficult solutions and heavy calculations caused by solving nonlinear localization equations, the equations are transformed from nonlinear to linear by eliminating the second-order terms. Then, for the ill-conditioned problem of the localization equations caused by the antenna array positions and time difference errors, the equations are optimized by centralization and row balance to reduce their ill-conditioned degree. Finally, the Tikhonov regularization method is used to solve the localization equations with an ill-conditioned problem, and then, the PD position is determined. The experimental results show that the proposed localization algorithm can improve the accuracy of PD localization in substations and that the localization errors are within 2.23 m.

The near-field ultrahigh-frequency (UHF) quadruple-loop antenna (QLA) with uniform field distribution for item-level tagging is proposed. The proposed antenna consists of quadruple fan-shaped small loops and the middle feeding lines of each loop located at the top and bottom of the substrate using vias. The currents flowing through feeding lines are cancelled due to opposite directional currents (ODCs), and the proposed QLA operates as one large loop electrically. From this configuration, the proposed antenna achieves more uniform field distribution and a precise interrogation zone than conventional loop antennas. Compared to the conventional loop antennas with different sizes, the proposed antenna using the uniform field distribution achieves a interrogation zone of 40 × 40 mm $^2$ at up to approximately 50 mm.

As partial discharge (PD) monitoring has become a significant means of insulation fault diagnosis, built-in UHF sensors is increasingly adopted in GIS. In this letter, we report a hypersensitive triple-band optical PD sensor which is combined to a UHF sensor with an existing flange assembled on GIS. By experiments performed on an 110 kV GIS chamber, it demonstrates that with the spectral information obtained by this novel optical sensor, the discharge severity evaluation and the multi-source discharge clustering can be realized without any signal strength and phase-resolves statistics, which has a practical significance for the fault diagnosis of HVDC equipment such as DC GIL and DC bushing.

Radio frequency interference (RFI) is a critical problem for ultra-wideband synthetic aperture radars (UWB SAR) because the VHF/UHF band used by them is shared by other systems as well. A number of solutions have been proposed over the years. Recently, sparsity and low-rank estimation-based solutions were shown to perform better than traditional methods such as adaptive notch filtering. These algorithms model the SAR signal to be sparse and the RFI to be either sparse or low-ranked in nature and solve an optimization problem to estimate the SAR signal and RFI simultaneously. Algorithms in this class share the common characteristic that the SAR signal sparsity is captured by modeling each data vector as a linear combination of shifted SAR pulses. This data model addresses the structure of SAR signals in the down-range direction, but the inter-aperture cross-range structure, i.e., the fact that SAR signals add coherently across the cross-range, has been completely ignored. In this work, we incorporate this “global” 2-D structure of the SAR data into the RFI mitigation problem. Two algorithms are proposed: 1) (2-D) sparse SAR and sparse RFI estimation and 2) (2-D) sparse SAR and low-rank RFI estimation. The experimental results demonstrate that the 2-D model does a much better job of capturing the sparsity of SAR and the 2-D algorithms consistently perform better than the “local” 1-D algorithms. The level of improvement rises significantly in challenging cases—when the noise level and/or the number of RFI bands increases. Experiments are conducted extensively on simulated data sets as well as real SAR and RFI data sets collected by the U.S. Army Research Laboratory (ARL) to validate the proposed framework.

Optically transparent conductors (TCs) have been implemented and adopted into next-generation transmission lines and other RF structures from UHF to millimeter-wave (mmWave) applications. A current method of evaluating the performance of optically TCs uses a figure of merit (FOM) which is frequency agnostic. A new FOM for optically TCs at RF, microwave, and millimeter-wave frequencies is presented and provides distinction to the TC FOM proposed in 1976 where it adds a frequency dependence, by incorporating the skin effect requirement. A detailed analysis of the new FOM for both transparent conducting oxides and mesh conductors is presented and compared using TC literature data analyzed at 24 and 240 GHz where large FOM variation is shown. The manuscript shows the new RF FOM and classical FOM can vary by up to a factor of 10 when the skin depth of the conductor is not considered.

Laser texturing has been carried out on the surface of the silicone nano‐micro composites to achieve super hydrophobic properties, and water droplet‐initiated Corona discharge studies were carried out. The Corona inception voltage (CIV) exhibits considerable enhancement with increase in the nano filler content under DC voltage compared with AC voltage. The corona inception voltage is high with the textured surface and is found to have direct correlation with contact angle of the composite specimen. The Corona inception voltage was measured using Ultra‐high frequency (UHF) and fluorescent fibre techniques. It is observed that the fluorescent fibre technique is more sensitive in identifying discharges. Frequency domain analysis of UHF signal shows a dominant frequency at 1 GHz and for fluorescent signal, the spectral content is in the range of DC to 10 MHz. The rise time and pulse width of the UHF signal increases with the increase in the nano filler in composite material. The energy content of UHF/fluorescent signal due to discharges shows similar trend with its increase in energy with variation in its magnitude of the signal formed. The pulse width of fluorescent signal formed due to water droplet‐initiated discharges under AC and DC voltage is almost the same, and with the textured specimen it is quite low than the non‐textured material.

Purpose In manufacturing environments, mobile radio frequency identification (RFID) robots need to quickly identify and collect various types of passive tag and active tag sensor data. The purpose of this paper is to design a robot system compatible with ultra high frequency (UHF) band passive and active RFID applications and to propose a new anti-collision protocol to improve identification efficiency for active tag data collection. Design/methodology/approach A new UHF RFID robot system based on a cloud platform is designed and verified. For the active RFID system, a grouping reservation–based anti-collision algorithm is proposed in which an inventory round is divided into reservation period and polling period. The reservation period is divided into multiple sub-slots. Grouped tags complete sub-slot by randomly transmitting a short reservation frame. Then, in the polling period, the reader accesses each tag by polling. When tags’ reply collision occurs, the reader tries to re-query collided tags once, and the pre-reply tags avoid collisions through random back-off and channel activity detection. Findings The proposed algorithm achieves a maximum theoretical system throughput of about 0.94, and very few tag data frame transmissions overhead. The capture effect and channel activity detection in physical layer can effectively improve system throughput and reduce tag data transmission. Originality/value In this paper, the authors design and verify the UHF band passive and active hybrid RFID robot architecture based on cloud collaboration. And, the proposed anti-collision algorithm would improve active tag data collection speed and reduce tag transmission overhead in complex manufacturing environments.

An inward-looking wearable antenna can be used for radio communications with internal transceivers in vivo. The radio transmissions are recorded using an array of electric field sensors on the skin. This paper reports the effect of living tissue on a small cavity-backed slot antenna pressed onto soft tissue of the human torso at 2.09 GHz. In-vivo measurements were made on the skin surface at 13 torso locations using eight participants (age range, 22-68 years old), with body mass index ranging between 20.3 and 31.6 kg/m2 . Ultrasound imaging was used to determine the skin and fat thickness at every measurement location. The variation in the antenna input impedance measurements demonstrated that the human tissues (fat and muscle) affect the antenna impedance but the mismatch creates field strength measurement errors of less than 2 dB. Fat thickness in the range of 3-30 mm can slightly degrade the performance of these wearable antennas. These effects can be partly mitigated by selective location and antenna retuning to improve transceiver communications. Bioelectromagnetics. 2021. © 2021 Bioelectromagnetics Society.

A novel dual-band ultrahigh-frequency (UHF) radio frequency identification (RFID) sensor tag, designed to operate on metallic surfaces, is proposed. This particular UHF RFID sensor tag is capable of operating in both the main RFID frequency bands of the European Telecommunications Standards Institute (ETSI) and the Federal Communication Commission (FCC). The dual-band operation of the UHF RFID sensor tag is based on a very simple concept; by flipping the UHF RFID sensor tag on a metallic surface, it can operate either in the ETSI or FCC RFID frequency bands. The impedance and radiation characteristics of the UHF RFID sensor tag are presented with an extensive analysis of the effects of the metallic surface on the UHF RFID sensor tag. In addition, an equivalent model of the UHF RFID sensor tag, which includes the effects of the metallic surface on the sensor tag, is proposed. The UHF RFID sensor tag has a small form factor and presents a satisfying read range of around 3 m for both the operating frequency bands in a metallic environment as well as a read range of 1.4 m when operating in free space.

The Internet of Things (IoT) in extreme environments, such as underground and underwater, is an essential technology to monitor the status and exploit resources therein. Existing solutions using active UHF radios experience high power consumption and high signal propagation losses, which increase the cost of maintenance. In this article, a low-power IoT technology using passive sensors and near field communication (NFC) is introduced. Existing magnetic induction-based NFC and other communication protocols are reviewed, and their advantages and limitations are identified. Then the system framework, key technologies, and research challenges of the low-power long-range NFC-based passive sensing system are discussed. This system can enable ubiquitous sensing and computing in various inhomogeneous extreme environments. Its applications in precision agriculture, road infrastructure monitoring, and water quality monitoring are presented.

Microsatellites in LEO usually utilize amateur radio frequency (RF) to communicate with the ground station. For communication with the Earth, the very high frequency/ultrahigh frequency (VHF/UHF) range is utilized in most of the microsatellites telemetry tracking command (TTC) subsystems. Communication is the only vital way for recognition of CubeSat when it launches into its orbit; therefore, this subsystem is required to be designed with a very accurate RF circuit. As a result, this TTC subsystem has been implemented intelligently based on three separated PCBs, receiver, transmitter, and filters. This innovative procedure for implementing the TTC board give this opportunity that every component could operate and be simulated individually and malfunctioning is easier to detect. Eventually, frequency responses for every RF block-circuit is investigated practically and an engineering CubeSat standard TTC board model is fabricated.

In recent years, RF identification (RFID) technology in the ultrahigh-frequency (UHF) range has become increasingly important in many applications, especially in the context of both the Internet of Things (IoT) and Industry 4.0. RFID is no longer simply a matter of identification; today, it is mainly concerned with recording data from the surrounding environment. As a result, researchers are working on the integration of sensors (or even small actuators) in passive RFID transponders (tags) for a variety of different applications and also on the localization and tracking of RFID tags attached to various objects and machinery. Another key aspect in UHF RFID technologies is security, as the data transmitted may be confidential and should not be shared with third parties. For the fast verification of novel algorithms in localization and novel protocols for security, wireless testbeds allow swift verification of these designs under real-world or real-time conditions [1]. Wireless testbeds are widely used in research and require scalability, modularity, and extendibility of the hardware and software. These needs can be achieved by using software-defined radios (SDRs). In the case of UHF RFID, SDR-based RFID readers have been developed and used as wireless testbeds for enhancements in UHF RFID systems.

In this article we aim to increase the range of commercial passive UHF RFID technology. We propose a prototype forward-link repeater, which consists of a pair of antennas, a band pass filter, an RF power limiter and a low-noise amplifier (LNA). Initially, we focus on the design of the two antennas with inverse direction of circular polarization (CP), so that sufficient decoupling is ensured, while adhering to the following constraints: i ) the input antenna is circularly polarized to maximize the gain towards the reader’s antenna, ii ) the output antenna is circularly polarized to improve the probability of successful tag reception, given the expected randomness in the tag’s orientation, iii ) the volume of the entire structure is kept small. Then, we present the achieved range improvement of the proposed repeater in two applications: ${a}$ ) a fixed installation, where the reader successfully identified passive RFID tags from 60m and ${b}$ ) by placing the repeater on top of an autonomous robot, to provide power in distant battery-less RFID tags, while the robot randomly moves inside a large area. The robotic-repeater prototype achieved remarkable performance, inventorying distant passive RFID tags, under Non-Line-Of-Sight (NLOS) conditions with the reader, exploiting the robot’s mobility for fading-mitigation, combined with increased incident power from the repeater.

CubeSats have revolutionized the way scientists and students perceive space. The majority of CubeSat communication is greatly limited by the AX.25 standards, the small communication window, the available transmission power, and the available bandwidth at VHF/UHF band. As a result, CubeSat radios could only establish low data rate links which restrict the communication capabilities of a CubeSat mission. In this article, a brief review of current software-defined radios (SDRs) used in space missions is given. In addition, two different design methodologies for SDRs for CubeSats are proposed that can be used as a guideline for CubeSat developers. Finally, a high data rate SDR for the UOW CubeSat project is presented that address all the above limitations. The radio operates at S-band, employs quadrature amplitude modulation with a maximum data rate of 60 Mb/s consuming 2.6 Watts in transmit mode and 0.4 Watts in receive mode. The digital signal processing functions and the mode control of the radio are orchestrated by a field programmable gate array system-on-chip. The analog radio frequency domain is accommodated by a 4-layer printed circuit board with dimensions of 92 mm $\times88$ mm. The goal of the UOW CubeSat radio is an adaptive, on-flight reconfigurable communication platform that will revolutionize the current communication capabilities of the CubeSats and expand nanosatellites mission perspectives.

UHF near-field RFID reader antenna based on leaky waveguide is proposed and the performance is evaluated using numerical simulation and experiment. In order to suppress the standing wave along transverse direction, a pair of notches is placed on the transverse edge of the mesh layer of the planar waveguide. Diversity operation by switching impedance of the end terminal of the planar waveguide antenna is also introduced to suppress the standing wave effect along longitudinal direction. Numerical simulation and experiment show that the near-field null lines parallel to the longitudinal direction is almost removed by the presence of the notches and the distribution of the field strength becomes almost uniform because of the utilization of the switching diversity. It is demonstrated that the reading performance of the commercial RFID tags is greatly improved by using the proposed RFID reader antenna with the diversity operation of termination impedance.

In our age of global networks and the Internet of Things, communication and identification with a transponder tagged on goods and products have become increasingly important [1]. There is not only a need for the identification of the labeled objects but also for finding their exact positions in 3D space. Radio-frequency identification (RFID) offers both and is, in fact, already used in a vast field of applications, such as access control, goods logistics, indoor localization, automation, stocktaking, and many others [2]-[6]. Figure 1 illustrates a mobile robot platform for automatic inventory rounds that is used to acquire 3D product maps with ultrahigh-frequency (UHF)-RFID technology.

In this article, we discuss how one can make, with modern and low-cost tools, a software-defined ultra high-frequency (UHF) RF identification (RFID) reader. Since we have chosen to leave the discussion of the top-level reader implementation until the very end, an introductory outline is warranted to help guide our audience. We first provide the uninitiated with some background context by answering four questions: What is UHF RFID? How does it work? What happened with UHF RFID? And, finally, what's next? That is, how do we envision the technology evolving in the future with the support of a broad community? Second, we describe the fundamental metrics and performance budgeting of RFID readers. Following this, we provide an overview on how to design, make, and automatically tune two critical components of UHF RFID readers: the antenna and transmit leakage canceller. Third, we delve even further into details of the transmit leakage canceller. Finally, we describe the complete high-level architecture of a proposed low-cost reader.

A novel miniaturized dipole antenna design incorporating triple sleeves and shorting load leading to enhanced bandwidth is proposed in the present work. The Triple Sleeve Dipole Antenna with Shorti...

Introduction. This article refers to the authors’ calculation method for studying the effects UF 6 (uranium hexafluoride, UHF) on the human body. A review of this method’s main ideas and the features of the approach to solving the problem at certain stages of the movement of UHF from being released into the air before entering the body is offered. The possibilities of the proposed method and its place in many well-known studies in this direction are described. Material and methods. The research material is UHF. It serves as the primary working substance in technologies for enriching natural uranium with the 235 U isotope. UHF, due to various circumstances, appears in the production room in a gaseous state. A method for studying the effects of UHF on humans is to describe the distribution processes of UHF molecules in the volume of the working room, chemical transformations of UHF, physical transformations of the resulting products, i.e., all processes accompanied by the delivery of toxic substances and their transfer from the source to the person and before excretion from the body in a natural way. The description of these processes is carried out analytically. Results. Lists the results that can be obtained by calculation. Discussion. A discussion of the results is carried out in the following areas. The issue of the possibility of using the described calculation method to solve the problems of ensuring labor safety at work is considered. The question of trust in the calculated values characterizing the effect of UHF on the human body is being studied. To solve this problem, we compared the calculated results obtained for a particular process and the experimental ones implemented in a similar process. Conclusion. A conclusion is made regarding the advantages and disadvantages of the method under investigation for studying the effects of UHF on humans and determining their place among existing methods.

A new approach for modeling lead–lag relationships in high-frequency financial markets is proposed. The model accommodates non-synchronous trading and market microstructure noise as well as intraday variations of lead–lag relationships, which are essential for empirical applications. A simple statistical methodology for analyzing the proposed model is presented, as well. The methodology is illustrated by an empirical study to detect lead–lag relationships between the S&P 500 index and its two derivative products.

RFID, a key enabling technology of Internet of Things (IoT), has a broad development prospect in the device-free localization (DFL). The RFID-based radio tomographic imaging (RTI) method has received great attention from scholars, owing to its properties of good real-time performance, low computational complexity, high localization accuracy. However, RTI suffers from the influence of multipath and noise, which results in the artifacts and false targets appearing in the imaging result and, in turn, decreases the positioning performance significantly, especially when there are multiple targets. Therefore, how to recognize the locations and number of true targets from the imaging result becomes an urgent problem in multi-target positioning. To solve this problem, we propose a novel scanning circle link analysis (SCLA-RTI) method to eliminate false targets and locate real targets in UHF RFID scenario. First, scanning circle method is introduced to detect the line-of-sight (LOS) links through the detecting region of the local maximum pixel in the imaging result. After feature analysis and selection of the RSS change of links, the random forest classifier is used to determine the location and number of real targets. Experiments demonstrate that SCLA-RTI method has superior performance in an indoor environment, which can accurately identify true and false targets and obtain high localization accuracy.

Regulatory approval of ultrahigh field (UHF) MR imaging scanners for clinical use has opened new opportunities for musculoskeletal imaging applications. UHF MR imaging has unique advantages in terms of signal-to-noise ratio, contrast-to-noise ratio, spectral resolution, and multinuclear applications, thus providing unique information not available at lower field strengths. But UHF also comes with a set of technical challenges that are yet to be resolved and may not be suitable for all imaging applications. This review focuses on the latest research in musculoskeletal MR imaging applications at UHF including morphologic imaging, T2, T2∗, and T1ρ mapping, chemical exchange saturation transfer, sodium imaging, and phosphorus spectroscopy imaging applications.

This paper examines the impact of daily activities on the performance of a body‐mounted radio frequency identification (RFID) tag inkjet printed onto tattoo transfer paper. This paper aims to assess how robust RFID tags of this nature are when mounted on the skin while the user undergoes various daily activities. The factors considered for these robustness tests are the effect of sweat and wear and tear on these tags during everyday use and also how it stands up to being exposed to water and soap during showering. Performance assessment was carried out using parameters such as point‐to‐point surface DC resistance as well as read range. Results show marginal effects on the tag performance and the tag continued to function during a normal day's activities, which lasted for 8 h, and rigorous activities like exercising but stopped functioning when there was severe damage to tag.

In ultra-high frequency (UHF) band, conventional microwave absorbers are limited in application by their thickness or weight. In order to solve this problem, a novel double-sided and dual-tuned active frequency selective surface (AFSS) absorber for the UHF band is designed and implemented for the first time. The physical mechanism is analyzed by the equivalent circuit method (ECM) and current distribution. Non-coplanar bias circuits of p-i-n diodes and varactors are proposed and achieved by a double-sided structure. The Fano resonance introduced by double-sided structure is analyzed and suppressed. The proposed structure covers an ultrabroadband of 0.4–2.5 GHz (144.8% in fractional bandwidth) below −10 dB by changing the working states. The thickness is only $\lambda _{L}$ /30 in the lowest operating frequency, and the areal density is only 1.54 kg/m2. It is worth mentioning that the structure has good angular sensitivity and can be used to complex targets for low-RCS applications.

A distilled water dielectric resonator antenna (DRA) with a wide frequency-tuning range and high efficiency is presented in this article. It consists of a water resonator and a ground plane with a wideband bowtie feeding slot. The water resonator, having tunable dimensions, is employed to achieve frequency-reconfigurable characteristics. Mechanical switches and a microfluid pump are integrated to control the tuning process. The water DRA, with and without the liquid control system, is designed with a simulation tool and then fabricated and measured to validate the antenna's performance. It is demonstrated that the antenna exhibits high total efficiency (g80%) across a wide frequency-tuning range from 168 to 474 MHz (for S11, -10 dB) with a very compact volume of 278 t 278 t 131 mm3 (0.155l t 0.155l t 0.073l at 168 MHz). Compared with traditional reconfigurable antennas, this design provides a wider frequency-tuning range, a more compact size, and a higher degree of design freedom. It is therefore a promising candidate for very high-frequency (VHF) and ultrahigh-frequency (UHF) applications.

Especially after the launch of 7 T, the ultrahigh magnetic field (UHF) imaging community achieved critically important strides in our understanding of the physics of radiofrequency interactions in the human body, which in turn has led to solutions for the challenges posed by such UHFs. As a result, the originally obtained poor image quality has progressed to the high-quality and high-resolution images obtained at 7 T and now at 10.5 T in the human torso. Despite these tremendous advances, work still remains to further improve the image quality and fully capitalize on the potential advantages UHF has to offer.

The article considers a new method for calculating the attenuation of cellular signals during their propagation in the forested areas frequently occurring in the Astrakhan region (linden) and the regions where the above trees predominate. There are also discussed the empirical models of a radio wave propagation in the forested areas, such as a Weisberger model and a COST-235 model. There have been built the curves of signal losses on the routes derived by the new method. There was conducted the experiment determining the effectiveness of the developed method. The obtained method has been found efficient for improving the accuracy of the preliminary design of radio communication systems

In this paper, a backfire suppressed aperture coupled circularly polarized (CP) stacked patch antenna for universal ultra-high frequency (UHF) radio frequency identification applications is presented. Cross-polarized backfire radiation patterns were successfully suppressed by a planar high impedance surface (HIS) reflector. The size of the fabricated antenna is 250 × 250 × 26.9 mm3 (0.71λ0 × 0.71λ0 × 0.076λ0) and its peak gain value of 7.1 dBi is measured. The distance between the antenna and the HIS reflector is only 4.8 mm (0.014 λ0). The HIS reflector suppressed cross-pol backfire radiations by about 10 dB. Detailed antenna and HIS reflector design are discussed thoroughly in this paper. The presented backfire suppression technique using the HIS reflector is scalable to other applications and frequency bands. This paper demonstrates the feasibility of the HIS structure at UHF band.

The motivation of this paper increases the bandwidth of power amplifier to multioctave by matching circuit, which consists of ferrite balun, 4:1 transformers and RC network feedback to make atrade-...

This article presents a novel sensor-fusion method for indoor vehicle tracking. The phase of the signals backscattered by a set of Ultra High Frequency-Radio Frequency Identification (UHF-RFID) reference tags spread in the scenario is combined with the information acquired by on-board low-cost kinematic sensors. The RFID data are acquired by the on-board reader, during the relative motion of the vehicle with respect to the static reference tags, by resembling a synthetic-array approach, with an advantageous reduction of the reference-tag spatial density. In particular, such phase samples are combined with the kinematic data collected by odometers, through a sensor-fusion approach. The method capability is investigated through a numerical analysis that accounts for the main system parameters. Then, the tracking capability is demonstrated through a measurement campaign in a laboratory test set with a UHF-RFID robot prototype equipped with commercial encoders. Experimental results show an average localization error of centimeter order in the estimation of medium-length trajectories by employing only two reference tags in a relatively small area. The proposed method does not need for any calibration procedure and can be implemented by commercial off-the-shelf (COTS) hardware.

This article discusses the challenges and advantages of measuring radar cross section (RCS) using reflection coefficient measurements from a single-antenna test setup. In practice, arranging two ultrahigh-frequency (UHF) antennas in a quasi-monostatic configuration is difficult due to their large physical size. In addition, the coupling power between the two antennas can be much larger than the signal of interest, imposing further limitations on this configuration. However, traditional RF measurement hardware and postprocessing algorithms are combined to extract RCS across frequency and azimuthal angle accurately with the $S_{11}$ values collected from a single antenna. This is made possible by using vector background subtraction and time-gating windowing techniques to suppress multipath reflections, clutter, and mismatch reflection while increasing the measurement’s dynamic range. The test setup utilizes the National Instruments LabVIEW software for control and automation, a General Purpose Interface Bus (GPIB)-enabled vector network analyzer, and a rotary table allowing for experiments to be conducted in an anechoic chamber or an outdoor measurement range. Experiments are conducted at the University of Oklahoma in the far-field anechoic chamber and outdoors using the components mentioned above to validate the derived algorithms and measurement concepts. The chamber setup is calibrated using a metal sphere to extract the RCS of a smaller metal sphere. The initial RCS extraction had an average error of 4.9 dBsm over the 300–1000-MHz frequency range using only calibration and vector background subtraction. After applying time gating, the error is further reduced to 0.54 dBsm. The implemented test setup is accomplished using traditional measurement equipment and a single antenna allowing for a portable, flexible, and low-cost solution for RCS measurements in the UHF band.

Ultrahigh frequency radio frequency identification (UHF RFID) uses backscattered electromagnetic (EM) modulation techniques to communicate between readers and tags. The suppression of the carrier signal leaked from the transmission channel to the receiving channel is the key factor that determines the reader’s sensitivity. In this letter, a broadband, fast carrier cancellation technique is proposed. The reader system uses two transmission ports: one is for the transmission of the interrogating signal and carrier waves (CWs) and the other port can dynamically sample the leakage signal in the receiving channel and generate a cancellation signal with the same amplitude but opposite phase of the leakage. This technique is implemented using an AD9361 transceiver chip as RF front end and a field-programmable gate array (FPGA) board as the protocol and cancellation controller. Experiments demonstrate that a suppression of around 92 to 106 dB can be achieved within 0.5 ms in a UHF RFID system. The cancellation technique is also broadband; with a matched antenna, the experiment shows that cancellation can work effectively from 0.3 to 6 GHz.

To date, CubeSat radars and imagers have been limited to operations beyond S-band due to the challenges associated with the design of wideband, compact, low-frequency antennas. Concurrently, the frequencies at VHF/UHF bands can image through clouds and foliage, and are very attractive for ice, water and biomass sensing. There is thus a need to develop wideband antennas that can operate at VHF/UHF bands which are low cost, light-weight, and packable. In this paper, we present a CubeSat deployable Tightly Coupled Dipole Array (TCDA) that achieves VSWR

We propose an ultra high frequency (UHF) radio frequency identification (RFID, 902–928 MHz in the US) channel emulation testbed that is capable of simultaneously emulating unique wireless channels. The proposed system can potentially be an invaluable tool in the design and validation of RFID-based Internet of Things (IoT) sensors and systems. Emulation of ray-tracing-based wireless channels enables the evaluation of inherently difficult and complex radio frequency (RF) scenarios, particularly in situations when in-person experimentation is not feasible or desirable (e.g., during a pandemic or in a critical care facility). Furthermore, the emulation testbed is able to generate a large amount of sensor data in a limited time period. Machine learning techniques used in wireless IoT can be greatly enhanced by a large amount of data extracted from the emulation of dynamic and challenging environments. The proposed multi-channel emulation testbed is therefore a valuable solution for experimentation on real hardware and a convenient tool for pre-clinical-trial system validation.