Passive Antenna Research Articles

Near-Field HF-RFID and CMA-Based Circularly Polarized Far-Field UHF-RFID Integrated Tag Antenna

This research proposes an integrated high-frequency (HF) and ultrahigh-frequency (UHF) passive radio frequency identification (RFID) tag antenna for near-field (13.56 MHz) and far-field (920–925 MHz) communication. This tag antenna is advantageous for the applications with lossy material in the near-field communication and mitigates polarization loss in the far-field communications. The HF-RFID tag antenna is of square spiral structure, and the circularly polarized UHF-RFID structure consists of a square loop radiator with cascading loop feeding and shorted stub. The structure of HF-RFID tag antenna situated inside the circularly polarized UHF-RFID tag can avoid the significant effect of the near-field magnetic coupling from the square loop. The UHF-RFID tag antenna is realized by using characteristic mode analysis for wideband circular polarization. The HF-RFID structure is conjugate-matched with NXP NT3H2111 chip, and the UHF-RFID structure is conjugate-matched with NXP G2X chip. Simulations were carried out, and an antenna prototype was fabricated. The experimental results reveal that the radiation pattern of UHF-RFID tag antenna is bidirectional with a gain of 0.31 dBic. The impedance bandwidth covers the frequency range of 903–944 MHz, and the axial ratio in boresight direction at 922.5 MHz is 1.67 dB, with the axial ratio bandwidth over 863–938 MHz. The maximum near-field and far-field reading ranges are 4.9 cm and 8.7 m. The proposed integrated dual-band passive tag antenna is operationally ideal for HF-RFID and UHF-RFID applications.

Passive Beam-Steering Gravitational Liquid Antennas

We present a new concept to passively steer the antenna radiation beam to a fixed direction by utilizing the liquid fluidity behavior due to gravity. Completely different from existing technologies, the proposed antenna does not require any additional mechanical structures, phase shifting circuitry, liquid pumps, tunable elements, or their associated components. By properly designing the structure and resonant mode of the liquid dielectric resonator, the proposed passive antenna can automatically steer the radiation beam to the fixed and desired direction for communication upon physical reorientation of the antenna. An antenna prototype has been proposed with a fundamental resonant band of 1.4–1.8 GHz by using new liquid materials, while its passive beam-steering feature has been experimentally verified. This simple, elegant, and low-cost antenna has combined the gyroscopic correction, gravity, and beam steering into one for the first time, presenting significant implications for radio communications and radar systems that demand an adaptive antenna beam in certain directions.

NaviSoC: High-Accuracy Low-Power GNSS SoC with an Integrated Application Processor

A dual-frequency all-in-one Global Navigation Satellite System (GNSS) receiver with a multi-core 32-bit RISC (reduced instruction set computing) application processor was integrated and manufactured as a System-on-Chip (SoC) in a 110 nm CMOS (complementary metal-oxide semiconductor) process. The GNSS RF (radio frequency) front-end with baseband navigation engine is able to receive, simultaneously, Galileo (European Global Satellite Navigation System) E1/E5ab, GPS (US Global Positioning System) L1/L1C/L5, BeiDou (Chinese Navigation Satellite System) B1/B2, GLONASS (GLObal NAvigation Satellite System of Russian Government) L1/L3/L5, QZSS (Quasi-Zenith Satellite System development by the Japanese government) L1/L5 and IRNSS (Indian Regional Navigation Satellite System) L5, as well as all SBAS (Satellite Based Augmentation System) signals. The ability of the GNSS to detect such a broad range of signals allows for high-accuracy positioning. The whole SoC (system-on-chip), which is connected to a small passive antenna, provides precise position, velocity and time or raw GNSS data for hybridization with the IMU (inertial measurement unit) without the need for an external application processor. Additionally, user application can be executed directly in the SoC. It works in the −40 to +105 °C temperature range with a 1.5 V supply. The assembled test-chip takes 100 pins in a QFN (quad-flat no-leads) package and needs only a quartz crystal for the on-chip reference clock driver and optional SAW (surface acoustic wave) filters. The radio performance for both wideband (52 MHz) channels centered at L1/E1 and L5/E5 is NF = 2.3 dB, G = 131 dB, with 121 dBc/Hz of phase noise @ 1 MHz offset from the carrier, consumes 35 mW and occupies a 4.5 mm2 silicon area. The SoC reported in the paper is the first ever dual-frequency single-chip GNSS receiver equipped with a multi-core application microcontroller integrated with embedded flash memory for the user application program.

Design of Coplanar Slotted SIW Antenna Arrays for Beam-Tilting and 5G Applications

A new solution for feeding the engraved slot antennas based on the substrate integrated waveguide (SIW) technology is presented in this letter. The structure is designed to operate at 25 GHz for beam-tilting and fifth-generation applications. Here several passive SIW slot antennas are proposed to cover an area from −56° to +56° with an offset of 10° at the operating frequency without using any phased shifter, in order to limit the losses. This new feeding approach is developed by using associated SIW holes to excite differently the centered slots located on the SIW structure broad face via coplanar lines. The electrical phase shifts are controlled by the position and number (one or two) of coplanar lines, and the combined slot configurations achieve beam-tilting function.

Longest-Range UHF RFID Sensor Tag Antenna for IoT Applied for Metal and Non-Metal Objects.

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 mm3 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).

Washing Durability of PDMS-Conductive Fabric Composite: Realizing Washable UHF RFID Tags

In this letter, we present experimental investigations on washing durability of a polydimethylsiloxane (PDMS)-conductive fabric composite to validate its applicability for the realization of flexible wearable antennas that can withstand multiple washing cycles. For this purpose, we designed an ultrahigh-frequency (UHF) radio frequency identification (RFID) passive tag antenna and fabricated several prototypes using such materials combination. Understanding the challenge of having a robust integration of a lumped electronic component (e.g., RFID IC) on a flexible antenna, a new way to improve the interconnection has also been investigated. The tag prototypes were subjected to recurrent machine-washing tests, and after each washing cycle, their performance was analyzed mainly in terms of the read range. The results reveal that, with a proper treatment on the antenna–IC fixture interconnection, the tag antennas developed with the PDMS–conductive fabric composite can maintain their performance very well, showing a minimum degradation in the read range after 15 cycles of washing.

Compact Wearable Meta Materials Antennas for Energy Harvesting Systems, Medical and IOT Systems

Demand for green technologies and green energy is in continuous growth in the last decade. Compact efficient radiators are very important for energy harvesting portable systems. Small antennas have low efficiency. The efficiency of communication and energy harvesting systems may increase by using efficient passive and active antennas. The system dynamic range may be improved by connecting amplifiers to the printed antenna feed line. Design, design considerations, computed and measured results of wearable meta-materials antennas with high efficiency for energy harvesting applications are presented in this paper. The antennas electrical parameters on human body were analyzed by using commercial full-wave software. The wearable antennas are compact and flexible and are 1.6 mm thick. The directivity and gain of the antennas with Split-ring resonators (SRR), is higher by 2 dB to 3 dB than the antennas without SRR. The resonant frequency of the antennas without SRR is higher by 5% to 10% than the antennas with SRR.

Maxwell Fisheye Lens Based Retrodirective Array

A Maxwell fisheye lens using parallel plate index grading is presented in this study to develop a passive retrodirective antenna array. As a proof-of-concept a design frequency of 10 GHz was selected for fabrication and experiment. The design principals of the lens are discussed, which enables 85% energy flow at the drain probe (also referred to as image point) of the lens. It is shown that the image in the Maxwell fisheye lens has a point symmetry with a reverse phase, which makes it possible to realize passive retrodirective action using the lens. This arrangement is significantly more practical than previous passive retrodirective topologies due to the un-constrained number of connections to radiating elements that it can support without the need for multi-layer technology. In the realization described here, a cross-polarized microstrip patch antenna array is connected to the source and drain probes of the lens structure in order to form the retrodirective array. The strategy for selecting the optimal transmission line lengths required to connect the antennas to the lens for maximum re-radiation power is described and implemented. Experimental results for a prototype high efficiency passive retrodirective array based on the theoretical design considerations presented in this paper are reported.

Features of the transmission of microwave signals at offshore facilities

In the article the capabilities of microwave signals transmission by fiber-optic communication lines on marine objects is considered. The features of constructing a scheme for transmitting a microwave signal from a passive antenna over a fiber-optic communication line are established. The technical solutions for optimizing the design of a fiber-optic communication line are proposed. The results of experimental investigations of fiber-optic communication lines parameters are presented.

Frequency-Scanned Monopulse Pattern Synthesis Using Leaky-Wave Antennas for Enhanced Power-Based Direction-of-Arrival Estimation

The synthesis of frequency-scanned monopulse radiation patterns using an array of two leaky-wave antennas (LWAs) is demonstrated. The LWA array must be designed with appropriate shifted frequency-dispersion responses to fulfill the desired monopulse-scanning specification over the required bandwidth and number of channels. This is demonstrated using two manufactured LWAs in half-width microstrip technology, designed to scan in the band from 2.39 to 2.65 GHz covering a field of view (FoV) from −80° to +80° and using three frequency channels. Also, this paper addresses the procedure to estimate the direction of arrival (DoA) of an incoming beacon RF signal composed by prescribed tones distributed in the scanning band. This type of multicarrier beacon signals can be produced in wireless systems which allow for frequency-hopping operation. It is demonstrated that the proposed monopulse DoA-estimation technique combines good angular resolution and wide FoV using a simple passive antenna structure.

Unified OSTBC‐based communication scheme for cooperative space vehicles

In many spatial cooperative vehicle networks, omni-directional communication is preferred due to its flexibility for networking. In the recent studies, space time code was shown to be an effective approach for improving the performance of the omni-directional communication between space vehicles. This paper studies the unified scheme for the orthogonal space time block code–based transmission between two space vehicles equipped with different numbers of antennas. It is obtained that at most six passive antennas and four RF chains are enough for the typical use. In the proposed scheme, the receiver can perform a unified detection procedure regardless of the actual number of the transmit antennas, which facilitates the practical application. Simulation results validate the proposed scheme in terms of the cumulative distribution function of the received signal-to-noise ratios.

High efficient plasma generation in an inductively coupled plasma using a passive resonant antenna

We developed a high efficiency plasma source in an inductively coupled discharge using a passive resonant antenna, which has the advantage that it could be retro-fitted to existing reactors with minimal change to the reactor. At the resonance, the source has a larger total equivalent resistance that is 3–18 times larger than that at the non-resonance. As the resistance increases at the fixed RF power, the RF current decreases accordingly, which indicates that the power loss in the powered antenna including the impedance matching circuits is significantly reduced. The experimental result shows that the power transfer efficiency is improved by about 30%–70% and the plasma density at the resonance increases 2–8 times higher than that at the non-resonance. For analysis, three-winding transformer model is developed. The experimental results are consistent with the model.

UWB Active Antenna for Microwave Breast Imaging Sensing Arrays

An ultrawideband (UWB) active slot antenna for tissue sensing arrays is developed and measured to operate from 3 to 8 GHz. The sensing element reported here is to be used in the imaging of the breast. It integrates a low-noise amplifier (LNA) with a printed-slot antenna to achieve gain enhancement of about 20 dB. The first prototype integrates the biasing of the LNA on the same board as the antenna. The second prototype uses an external bias tee providing dc power to the LNA through the coaxial connector of the active antenna. Both prototypes achieve the expected gain enhancement in comparison with the passive antenna element.

Different Substrate Materials for Designing a Passive UHF RFID Tag Antenna

The Radio Frequency Identification (RFID) technology has been increasingly used for various application such as tracking of products, smart cards, identification, item management, security etc. In this paper, the performance parameter of the passive UHF RFID tag antenna has been studied for four different substrate materials viz., FR4 epoxy, PET, Rogers 4350, Taconic TLY materials. A simple meandered dipole antenna has been designed using a T-match stub for impedance matching of the tag antenna with the attached RFID chip. These different substrates are then designed separately, for the same antenna geometry. The effect of using these substrates on RFID tag antenna parameters such as reflection coefficient, antenna gain, VWSR, radiation pattern, impedance, ease of optimization level, read range, and radiation efficiency are then observed.

A Configurable Dielectric Resonator-Based Passive Wireless Sensor for Crack Monitoring

Since infrastructures are frequently exposed to atmosphere and stress, e.g., costal infrastructure, railway track, pipeline, service-induced cracks occur. Recently, passive wireless antenna sensors are emerging for early crack detection and life-long monitoring. However, the mode distribution challenges the direction stability in crack detection. Enabling by a cylindrical dielectric resonator (CDR), this communication proposes a passive wireless sensor for ubiquitous crack monitoring. The proposed CDR can excite a HE $_{ {11\delta }}$ mode and its polarization can be configured through the change of the polarization of the incident wave. Due to the high dielectric substrate selected, the proposed CDR has a compact size of 24.0 mm (diameter) $\times \,\, 9.0$ mm (height). By confining the near-field energy into a small magnetic wall, the CDR is naturally turned into a sensitive crack sensor. Crack growth causes a continuous shift in the resonant frequency of the radar cross section (RCS). This behavior can be wirelessly monitored in a distance of 0.25 m through a horn antenna. For a fixed crack width of 2.0 mm, the sensitivity in crack depth characterization is 25.4 MHz/mm. Due to the absence of electronic device and metal, the proposed sensor can work in extreme conditions, e.g., high-temperature environment.

Scattering of Microwaves by a Passive Array Antenna Based on Amorphous Ferromagnetic Microwires for Wireless Sensors with Biomedical Applications.

Co-based amorphous microwires presenting the giant magnetoimpedance effect are proposed as sensing elements for high sensitivity biosensors. In this work we report an experimental method for contactless detection of stress, temperature, and liquid concentration with application in medical sensors using the giant magnetoimpedance effect on microwires in the GHz range. The method is based on the scattering of electromagnetic microwaves by FeCoSiB amorphous metallic microwires. A modulation of the scattering parameter is achieved by applying a magnetic bias field that tunes the magnetic permeability of the ferromagnetic microwires. We demonstrate that the OFF/ON switching of the bias activates or cancels the amorphous ferromagnetic microwires (AFMW) antenna behavior. We show the advantages of measuring the performing time dependent frequency sweeps. In this case, the AC-bias modulation of the scattering coefficient versus frequency may be clearly appreciated. Furthermore, this modulation is enhanced by using arrays of microwires with an increasing number of individual microwires according to the antenna radiation theory. Transmission spectra show significant changes in the range of 3 dB for a relatively weak magnetic field of 15 Oe. A demonstration of the possibilities of the method for biomedical applications is shown by means of wireless temperature detector from 0 to 100 °C.

Amplifier type active antenna at 2.45 GHz for wireless applications

In this paper, an active antenna is proposed, where microwave amplifier is directly integrated on passive antenna. The amplifier provides required RF power to the antenna, hence improves the system efficiency. This paper presents a slotted patch antenna, resonating at 2.45 GHz for Industrial Scientific Medical band, having excellent return loss of − 30 dB and radiation efficiency of 100%. The microwave amplifier was designed and optimized on AWR Microwave Office software for 11 dB gain and noise figure less than 2 at the frequency of 2.45 GHz. The proposed amplifier type active antenna was designed using FR4 substrate with substrate height, 1.6 mm and dielectric constant of er = 4.4. In active antenna, amplifier provides extra power to the antenna while electric parameters of active antenna are same, such as return loss is − 21.95 dB at 2.11 GHz and the improved bandwidth of 125 MHz. The passive antenna is designed, analyzed and optimized on IE3D Zeland software version 15.30.

Gain Enhancement of a Looped Slots Patch Antenna for Passive UHF RFID Tags Applications in Metallic Supports

The objects with high conductivity such as metals consist of a challenge for passive RFID (Radio Frequency IDentification) tags in UHF (Ultra High Frequency) due to their effects on tags antennas performance. In this paper, a passive antenna for UHF RFID tags applications on metallic supports is presented. The antenna structure is constituted of a rectangular patch with looped slots printed on three-layer substrate and deposited on a regular ground plane. The looped slots are used to match the antenna impedance to the chip impedance in order to maximize power transfer. The three-layer substrate is adopted to improve the antenna gain, and the regular ground plane is added to act as fixed-size metallic plate. The antenna performance in free space and the one attached to the metallic surfaces are compared. The metallic plate size variation effects on antenna performance are studied by fixing the proposed antenna over different sizes of square copper plates which are multiple to the antenna size, and evaluated using the 3D electromagnetic simulator: HFSS (High Frequency Structure Simulator). The proposed antenna is designed to be used on high dimensions metallic objects such as the containers. It achieves a stable performance when the metallic surface size is five times larger than the antenna size: a read range of 16 m, an antenna gain about 2.5 dB and a bandwidth that covers all passive UHF-RFID band.

Passive parasitic UWB antenna capable of switched beam‐forming in the WLAN frequency band using an optimal reactance load algorithm

Passive parasitic UWB antenna capable of switched beam‐forming in the WLAN frequency band using an optimal reactance load algorithm

Passive Wireless UHF RFID Antenna Label for Sensing Dielectric Properties of Aqueous and Organic Liquids

The in situ wireless sensing of dielectric properties for organic aqueous solutions with a wide range of relative permittivities is presented. The use of an ultra-high frequency passive label antenna design attached to either clear borosilicate glass bottle or Petri plate is proposed, which allows for the unobtrusive, safe monitoring of the liquid solutions. The meandered dipole antenna (with a parasitic loop matching component) frequency is highly reliant on the chosen container as well as on the liquid present within, and adjusts with shifting dielectric properties. Tested solutions of high-relative permittivity (such as water) along with low permittivity, lossy liquids (such as xylene) presented distinctive frequency characteristics with read distances of up to 7 m for each type of container tested. The sensor was also able to detect `unknown' solutions and determine the dielectric properties by utilizing standard curve analysis with an accuracy of ±0.834 relative permittivity and ±0.050 S · m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> conductivity (compared to a standard dielectric measurement system available on the market). With the accuracy known, tuning the design to fit any necessary frequency is possible as a means to detect specific changes in any one liquid system. This sensor is a possible candidate for discreet real-time monitoring of liquid storage containers and an alternative for low-cost bulk liquid dielectric property identification, which could be implemented in areas requiring, constant, or remote monitoring as needed.