Passive Antenna Research Articles

Scan-Loss Compensation for Full-Azimuth Multi-Facet Phased Array Antennas

An approach to compensate scan losses displayed by full-azimuth multifacet phased arrays is proposed in this article. This approach is based on a constructive superposition of scanned beams from adjacent array panels resulting in enhanced composed coverage. Said constructive superposition is achieved by coordinating the insertion phase shifts applied at the array element level. Special attention is given to panel arrays arranged in equilateral triangle and square prisms. The benefits of the proposed beamforming approach are validated by full-wave simulations, as well as passive antenna measurements taken on physical prototypes. The achieved improvement in equivalent isotropically radiated power (EIRP) excessively compensates for the experienced scan loss and reaches 6 dB at the maximal scan angles. An additional advantage of the developed methodology consists in the mitigation of the composed beam squint at wide scan angles.

Passive RFID microstrip photosensitive sensor based on TiO2/rGO/CuO composite

In this paper, a passive RFID microstrip antenna photosensor based on titanium dioxide (TiO2)/reduced graphene oxide (rGO)/copper oxide (CuO) nanocomposite was designed and fabricated for monitoring light intensity in the environment. The microstrip patch antenna with slot is designed by HFSS simulation, the actual antenna is prepared by the engraving machine, and the photosensitive RFID sensor is prepared by coating the nano-material on the antenna by drop coating. The amplitude of ambient light intensity is determined in the frequency band of 2.082 GHz–2.087 GHz. To study its performance, the sensor coated with the sensitive material was tested under a solar simulator. The results show that from the dark environment (0 klx)-32.9 klx light intensity, the sensitivity of the photosensor is 0.106 ± 0.03 db/klx, and the sensitivity is 0.784 ± 0.08 db/klx under the light intensity of 36.8–53.9 klx. The response time of the photosensor was 20.1 s and the recovery time was 30.3 s in the light intensity range of 0–53.9 klx, indicating that the TiO2/rGO/CuO composite has good responsiveness and repeatability as a photosensitive material.

Design of Dielectric Resonator Antenna Array With Wide-Angle Scanning Based on Dual Magnetic Currents

A wide-beam dielectric resonator antenna (DRA) and its related phased array with wide-angle scanning are presented in this article. To improve the scanning coverage and cross polarization discrimination (XPD) simultaneously, the wide-beam method utilizes dual magnetic currents (MCs) in the same direction. The operating principle is theoretically analyzed using suspended MC theory. Two wide-beam DRAs working in TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{y}_{1\delta 1}$ </tex-math></inline-formula> and TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{y}_{1\delta 3}$ </tex-math></inline-formula> modes with parasitic loops are studied to verify the presented beam-broadening method. The simulated 3 dB beamwidths of the two DRAs are higher than 205° and 140° in the E- and H-planes, respectively. Two wide-beam DRAs operating at 5.5 GHz were fabricated and measured. Based on the wide-beam DRA element, the passive eight-element array antenna and three feeding networks corresponding to scanning angles of 0°, 40°, and 80° were machined. The total array system is verified to have an enhanced beam scanning angle of ±85° with a gain fluctuation of 2.5 dB. The co-polarization is stable and the XPD is greater than 20 dB for any scanning angle.

Glasses frame‐based wearable antenna design for ultrahigh frequency radio frequency identification and Internet of Things applications using characteristic mode analysis

A novel ultra-high frequency (UHF) radio frequency identification (RFID) passive tag antenna based on a glasses frame is proposed for Internet of Things (IoT) applications. The glasses frame structure is exploited using characteristic mode analysis (CMA) to explore different modes for both 900 MHz and 2.4 GHz frequency bands. The proposed design consists of a glasses metallic frame and a loop for conjugate matching with an RFID chip (Alien Higgs H4). First of all, an already manufactured glasses metal frame structure is simulated in Computer Simulation Technology (CST) Microwave studio using CMA to get CM modes in the required RFID band. After that, a small loop is used along with the RFID chip as a capacitive coupling element to excite modes at 900 MHz by placing it at current minima. Moreover, the proposed tag antenna is also simulated with the voxel head model in CST and there is no significant change in impedance and reflection coefficient. The simulated specific absorption rate (SAR) is 0.5 W/Kg. Furthermore, the tag design is simulated with different glass materials and also with different frame structures to prove the robustness of the proposed solution. This tag design covers the entire US UHF RFID band (902–928 MHz) and features a read range of 2 m, measured using a UHF RFID reader setup with 4 W EIRP. Therefore, this antenna design can be a good candidate for future IoT technologies such as RFID, long range (LoRa), and other IoT applications.

Multibeam Antenna for Ka-Band CubeSat Connectivity Using 3-D Printed Lens and Antenna Array

In this letter, the design of a passive multibeam lens antenna is proposed for the CubeSat space communication system as an alternative application of a 2-D microstrip antenna array that has originally been designed for a 39-GHz 5G multi-user, multiple-input, multiple-output (MU-MIMO) system. The half-ellipsoid lens is 3-D printed using stereolithography technology. The antenna prototype is capable of selecting the main beam between 16 different directions with a gain ranging from 14 to 16 dBi and a half-power beamwidth of 14 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> –18 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> . The measurements carried out in an anechoic chamber show good agreement with numerical simulations. The presented prototype shows that by employing 3-D printing technologies existing antennas can be easily and inexpensively converted to switched-beam or multibeam solutions.

A Parallel Robotic Antenna Design for Downlinking Leo Satellite Signal Subject to Wind Disturbance

Passive LEO (Low Earth Orbit) satellites are a telecom premier option. However, LEO satellites impose not only stringent specifications on the resolution, precision and repeatability but also requiring advanced antenna technology for signal downlinking. To efficiently downlink LEO signals at each passage onto a given Earth region, we explored large size passive Earth antenna and an array of smaller size active Earth antennas to minimize the trajectory loss. To guarantee design specifications, the dynamics cannot be neglected given the size and inertia of base and antenna. In this paper, it is proposed the design, path planning and control of a six DoF robotic antenna maneuvering the antenna subject to aerodynamic wind disturbance. The system maneuvers to point at the LEO satellite over the whole envelope with the required precision to guarantee robust point-to-point tracking. Representative simulation results for three geolocations shows practical tracking with off-the-shelf-component actuators, without requiring any knowledge of the dynamics while withstanding state-dependent persistent disturbances.

Semi-Blind Channel Estimation for RIS-Assisted MISO Systems Using Expectation Maximization

<bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Reconfigurable intelligent surface (RIS) is a passive antenna array composed of a large number of reflecting elements. In a RIS-assisted communication system, it is a challenging task to acquire accurate channel state information (CSI). In this paper, we propose a semi-blind channel estimation method for a RIS-assisted massive multiple-input single-output (MISO) system. Assuming a Gaussian</b> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <b>priori</b> </i> <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on the data symbols, an iterative expectation maximization (EM)-based algorithm is developed to obtain the maximum likelihood (ML) estimate of the cascaded RIS channel. Different from existing pilot-based methods, the proposed semi-blind channel estimation method exploits the data symbols for channel estimation enhancement and only a fraction of full-pilot signaling overhead is required. Simulation results verify that the proposed method achieves significant improvement in the accuracy of the channel estimation while it noticeably reduces the training pilot overhead.</b>

Magnetoelectric Dipole Antennas Loaded With Meta-Lens for 5G MIMO Pattern Diversity Applications

This communication presents a unique design of a dual-polarized wideband passive beam-switching antenna at millimeter-wave (mm-wave) bands for multiple-input–multiple-output (MIMO) pattern diversity applications, which exhibits low correlation between the ports and a broad tilt bandwidth (BW). A magnetoelectric (ME) dipole fed by a printed ridge gap waveguide (PRGW) as a quasi-TE source is considered as the elementary antenna in the Ka-band. To achieve beam deflection in each quadrant, a four-port MIMO prototype consisting of four ME-dipoles, positioned perpendicular to each other, is integrated with a meta-lens that consists of three layers of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$12\times12$ </tex-math></inline-formula> dual-polarized split-ring resonators (SRRs) offset from the center of each antenna. The beamforming structure is able to generate four fixed beams, one in each quadrant at an elevation angle of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 40^{\circ }$ </tex-math></inline-formula> with respect to the broadside direction by exciting each port sequentially, while the other ports are terminated. Moreover, the proposed orthogonal structure contributes to low correlation between the four ports, while achieving dual-polarization, which highlights the suitability of the antenna for 5G mm-wave applications. The measured results from a fabricated prototype demonstrate a −10 dB impedance BW of 40% over 24–36 GHz, tilting BW of 32.2%, and a peak gain of 13.4 dBi at 29 GHz, while an isolation better than 30 dB is achieved over the whole frequency band. Moreover, a measured radiation efficiency in excess of 85% is obtained, due to the use of the low-loss PRGW feedlines.

Capacitively-coupled dual ring antennas for bolt loosening detection

This paper proposes a passive and wireless UHF (Ultra High Frequency, operating in 450–550 MHz) antenna sensor for bolt loosening detection. The novelty of this sensor is the introduction of nut’s rotation angle as sensing variable, achieving the whole process of bolt status monitoring, and easy installation enabling the sensor to be applied in in-service bolt loosening monitoring. The sensor consists of two concentric rings, and the overall size is 116 mm × 92 mm × 2.4 mm. When the bolt is loose, the nut’s rotation will change the coupling capacitance of the antenna and thus the resonant frequency. The electromagnetic performance of the sensor is simulated in HFSS and the quality factor calculated by HFSS is 52.87. Furthermore, the ability to characterize bolt’s status was validated in the experiments. The results demonstrate that the resonant frequency increases linearly with the loosening of the bolt (the correlation coefficient is 0.9789) and the antenna's sensitivity is 2.95 MHz/degree.

Millimeter-wave Passive Patch Antenna for Use in Wireless High-temperature Sensor

Millimeter-wave Passive Patch Antenna for Use in Wireless High-temperature Sensor

Noncontact Electromagnetic Wireless Recognition for Prosthesis Based on Intelligent Metasurface.

With the development of artificial intelligence and Internet of Things, hand gesture recognition techniques have attracted great attention owing to their excellent applications in developing human‐machine interaction (HMI). Here, the authors propose a non‐contact hand gesture recognition method based on intelligent metasurface. Owing to the advantage of dynamically controlling the electromagnetic (EM) focusing in the wavefront engineering, a transmissive programmable metasurface is presented to illuminate the forearm with more focusing spots and obtain comprehensive echo data, which can be processed under the machine learning technology to reach the non‐contact gesture recognition with high accuracy. Compared with the traditional passive antennas, unique variations of echo coefficients resulted from near fields perturbed by finger and wrist agonist muscles can be aquired through the programmable metasurface by switching the positions of EM focusing. The authors realize the gesture recognition using support vector machine algorithm based on five individual focusing spots data and all‐five‐spot data. The influences of the focusing spots on the gesture recognition are analyzed through linear discriminant analysis algorithm and Fisher score. Experimental verifications prove that the proposed metasurface‐based non‐contact wireless design can realize the classification of hand gesture recognition with higher accuracy than traditional passive antennas, and give an HMI solution.

2-D Orthogonal Multibeam Antenna Arrays for 5G Millimeter-Wave Applications

In this article, a 2-D <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$16 \times 16$ </tex-math></inline-formula> Butler matrix-based passive multibeam antenna array (MBAA) and a 2-D active–passive hybrid MBAA (APHMBAA) are both presented for fifth-generation (5G) millimeter-wave (mmWave) applications, which demonstrate that a 2-D coverage can be achieved by two types of 1-D beamformers in two orthogonal planes at analog beamforming level. For the 2-D passive MBAA (PMBAA), the 16 beams are controlled by two stages of substrate integrated waveguide (SIW) Butler matrices placed orthogonally. A novel 2-D interconnection method for connecting these two-stage Butler matrices is implemented based on the flexibility of the SIW without any connectors, cables, and soldering operations and then possesses the advantages of low cost, extensible, and integrated easily in the mmWave bands. The measured results exhibit that the operating bandwidth is 15.38% for the single-stage Butler matrix-based antenna array. Meanwhile, the maximal beam gain of the 2-D PMBAA is 9.4 dBi and its accurate beam directivity is also observed. For the 2-D APHMBAA, the multiple beams are generated by the Butler matrix-based passive beamformers in the vertical direction, whereas the beamforming on the horizontal direction is realized by the active networks utilizing mmWave active beamformer chips. Compared to the proposed 2-D PMBAA, the horizontal scanning performance of the hybrid framework is more flexible. What is more, its costs and complexity are both reduced tempestuously in comparison with an active multibeam array. The measured results show that the maximum measured beam gain of the array is 10.9 dBi and the chip channel gain is 27 dB. A wide 2-D spatial angle is covered simultaneously by the proposed hybrid beamforming scheme.

Design of a Chipless RFID Tag to Monitor the Performance of Organic Coatings on Architectural Cladding.

Coating degradation is a critical issue when steel surfaces are subject to weathering. This paper presents a chipless, passive antenna tag, which can be applied onto organically coated steel. Simulations indicated that changes associated with organic coating degradation, such as the formation of defects and electrolyte uptake, produced changes in the backscattered radar cross section tag response. This may be used to determine the condition of the organic coating. Simulating multiple aging effects simultaneously produced a linear reduction in tag resonant frequency, suggesting coating monitoring and lifetime estimation may be possible via this method. For coatings thinner than calculations would suggest to be optimum, it was found that the simulated response could be improved by the use of a thin substrate between the coated sample and the antenna without vastly affecting results. Experimental results showed that changes to the dielectric properties of the coating through both the uptake of water and chemical degradation were detected through changes in the resonant frequency.

High-Precise Microwave Active Antenna Sensor (MAAS) formulated for sensing liquid properties

In this study, a microwave active antenna sensor (MAAS) was designed and manufactured from PCB boards operating at a frequency of approximately 3 GHz to sense the characteristics of mineral oils (high voltage transformer oils) and chemical liquids such as methanol, chloroform, and ethanol. The proposed sensor has been designed using the automation software system named ADS (advanced design system). The antenna was linked with a radio amplifier; therefore, the antenna is called active antenna. As a result, the reflection coefficient changed from − 39.98 dB to − 66.26 dB, and also the quality factor changed from 350 to 27,000. The measuring and simulation results were quite identical in both active and passive antenna cases. An M-shaped channel with a capacity of 150 μL was built on a microscope glass slide, where the glass slide was placed in contact with the above face of the designed antenna (near field). That a slit channel was placed on the areas in which the electric field is concentrated. Then, the sensor was tested by injecting the channel with new and damaged transformer oil. Despite the small sample size, the amount of resonant frequency change was 2.23 MHz and 1.48 MHz for the active and passive antennas, respectively. A mathematical model was built to calculate the breakdown voltage of high voltage transformer oil, and the error value in the breakdown voltage value did not exceed ± 0.1606%. The other application of the antenna is to sense chemical liquids and to calculate the electrical permittivity of those samples by finding a mathematical model based on the resonant properties of the antenna. The measured permittivity of the liquids have been compared with the theoretical values, which gives a good qualitative agreement for our results.

Deflected beam pattern through reconfigurable metamaterial structure at 3.5 GHz for 5G applications

In this paper, the reconfigurable metamaterial is proposed to deflect the radiated beam of the bow-tie antenna at a 5G band of 3.5 GHz. The split square resonator (SSR) is designed at a sub-6 GHz band and reconfigured to produce different refractive indices. For obtaining the desired deflection angles, 3 × 7 SSR unit cells with ON and OFF configurations are printed into the antenna substrate. This arrangement creates two metamaterial configurations with different refractive indices in the closeness of the radiating elements, thereby deflecting the main beam to the direction of high refractive index metamaterial. In the passive beam deflection antenna, the reconfigurable SSRs deflect the radiation beam of the antenna by angles of ±39° in E-plane at 3.5 GHz. Furthermore, the embedding of SSRs helps improve the gain by 2.4 and 2.3 dB for the positive and negative deflection angles, respectively. On the other hand, in the active beam deflection antenna, the reconfigurable SSRs based on real PIN diodes can deflect the antenna radiated beam by angles of ±36° in the E-plane. These reconfigurable antennas have the potential to be used in 5G beam deflection applications. Both passive and active metamaterial antennas are fabricated, and their performances are measured.

Leveraging frequency agility of an MIMO antenna cluster with a transmitter IC

AbstractThis paper presents the prototype demonstration where an integrated transmitter circuit drives a mobile handset terminal antenna in order to provide frequency tunability and multiple input multiple output (MIMO) operation across the 0.5–4.5 GHz frequency range. The transmitter implementation incorporates on-chip weighted signal generation, i.e. amplitude and phase scaling to provide sufficient MIMO performance in the low band (700–960 MHz) and in the high band (1.5–4.5 GHz). In the transmitter, two antenna elements are used for MIMO operation in the low band and another two in the high band. The transmitter integrated circuit (IC) is fabricated in a 28 nm bulk CMOS technology with an active on-chip area of 0.2 mm$^2$. A custom antenna measurement procedure is proposed here in order to support and verify active antenna measurements with transmitter IC. A measurement procedure for the transmitter system comprising the transmitter IC and four antenna clusters is developed and discussed in comparison with traditional passive antenna measurements. The measurement results demonstrate that the transmitter IC driving the antenna clusters provides total antenna efficiency of $-6.5$ dB to $-1.5$ dB, and envelope correlation coefficient below 0.4 across the designated frequency bands. The results indicate that the implemented transmitter IC successfully tunes frequency response of the antenna clusters, and enhances the MIMO operation of such mobile antennas.

Wearable Circular Polarized Antennas for Health Care, 5G, Energy Harvesting, and IoT Systems

Novel circular polarized sensors and antennas for biomedical systems, energy harvesting, Internet of Things (IoT), and 5G devices are presented in this article. The major challenge in development of healthcare, IoT, 5G and communication systems is the evaluation of circular polarized active and passive wearable antennas. Moreover, a low-cost wearable sensor may be evaluated by printing the microstrip antenna with the sensor feed network and the active devices on the same substrate. Design considerations, comparison between simulation and measured results of compact circular polarized efficient sensors for wireless, 5G, energy harvesting, IoT, and medical systems are highlighted in this article. The electrical performance of the novel sensors and antennas on and near the user body were evaluated by employing electromagnetic software. Efficient passive and active metamaterial circular polarized antennas and sensors were developed to improve the system electrical performance. The wearable compact circular polarized passive and active sensors are efficient, flexible, and low-cost. The frequency range of the resonators, without Circular Split-Ring Resonators CSRRs, is higher by 4% to 10% than the resonators with CSRRs. The gain of the circular polarized antennas without CSRRs is lower by 2 dB to 3 dB than the resonators with CSRRs. The gain of the new passive antennas with CSRRs is around 7 dBi to 8.4 dBi. The bandwidth of the new circular polarized antennas with CSRRs is around 10% to 20%. The sensors VSWR is better than 3:1. The passive and active efficient metamaterials antennas improve the system performance.

Plasma and electrical characteristics depending on an antenna position in an inductively coupled plasma with a passive resonant antenna

We investigated the plasma and electrical characteristics depending on the antenna position in an inductively coupled plasma with a passive resonant antenna. When the powered antenna and passive resonant antenna are installed near the top plate and in the middle of the cylindrical reactor (setup A), respectively, the ion density at the resonance is about 2.4 times to 9 times higher than that at non-resonance. This is explained by the reduction in power loss in the powered antenna (including the matching circuits) and the increase in power absorbed by the plasma discharge. However, when the powered antenna and passive resonant antenna are interchanged (setup B), the ion density at the resonance is not significantly different from that at the non-resonance. When RF power is changed from 50 to 200 W, the ion density at the resonance of setup B is 1.6 times to 5.4 times higher than at the non-resonance of setup A. To analyse this difference, the profile of the z-axis ion density is measured and the electric and magnetic field simulations are investigated. The results are discussed along with the electron kinetics effect and the coupling loss between the antenna and the metal plate.

MODELING OF A LUNENBURG LENS ANTENNA WITH THE INNER METALIC SPHERE

One of the statutory principle of fifth generation mobile communications is the adaptive antenna system beam-forming technology that allow the radiation to be oriented to specific subscriber. Promising solution of the task can be using the passive antennas, which provide the direct beam-forming with no active component in the circuit, thus is low-cost. Lunenburg lens antenna is perspective solution of the task described above and allows the direct radiation to be formed in wide-angle range and keeps the required performance. Besides, it's slightly compact, so the antenna can be installed on various of city infrastructure elements, and the spherical form of device is advantage when the installation is performed on to the vehicles surface (train, car, aircraft, etc.) In the paper, the metallic sphere installation inside the spherical Lunenburg lens as a mean of attachment to constructions is described. The analysis results of the inner element impact to the antenna characteristics of the Lunenburg lens are provided. Analytical system model with the spherical conductor inside the antenna, which can also be used to calculate the presence of metallic particles impact to the average permittivity of the lens, is shown. The diffraction task is addressed by means of the Green's tensor functions application. The results of numerical modeling of the described antenna system using the Ansys Electronics Desktop (HFSS Design) are presented. Analytical and numerical calculations show that the limited-sized metallic sphere presence inside the lens does not significantly affect the focusing property of the device. The acquired formulas can be used in the future work to find the solution of the metallic element optimal radius approximation, using the neural networks as one of the mean to do it.

A Review on the Development of Spaceborne Membrane Antennas

The membrane antenna technology is a very promising approach to obtain large aperture with light weight and low stowed volume. In the past decades, extensive studies have been carried out on active and passive membrane antennas. However, the practical spaceborne applications are rare due to many challenges, e.g., the surface accuracy maintenance, the on-orbit reliability, and the environmental compatibility. This paper summarizes the history and state-of-art progresses on spaceborne membrane antennas. Curved surface reflectors, conformal active membrane antennas, planar array membrane antennas, and planar reflectarray membrane antennas have been introduced, respectively. Radiofrequency design, deploying mechanism, material, experiment, application, and analysis method have been presented. By concluding the advantages and challenges of the current membrane antennas, this paper is aimed at providing a perspective of the existing problems and future trend of spaceborne membrane antennas.