Wideband Behavior Research Articles

Two-axis beamsteering using a wideband Butler matrix and series-fed arrays for millimeter wave frequencies fabricated on metallic-nanowire-membrane platform

This work presents a two-axis beamsteering system designed for WLAN millimeter-wave frequencies. The system comprises a wideband Butler matrix and series-fed arrays. The Butler matrix, implemented with microstrip lines, features a wideband crossover with low phase imbalance, enabling four discrete beamsteering directions on the radiation H-plane. The series-fed arrays enable frequency-dependent beamsteering on the E-plane. The entire system was fabricated on a nanoporous alumina substrate using metallic-nanowire-membrane technology. Measurement results indicate an impedance bandwidth of 17.71%, which accommodates typical requirements for 60 GHz WLAN applications. Additionally, beamsteering in the desired directions was achieved. The presented Butler matrix structure stands out as one of the most compact found in the reviewed literature. The produced device successfully balances wideband behavior, compactness, and fabrication simplicity.

MICROSTRIP PATCH ANTENNA DESIGN WITH ENHANCED RADIATION EFFICIENCY FOR 5G 60 GHZ MILLIMETER-WAVE SYSTEMS

In this paper, a wideband, high-gain microstrip patch antenna design for 60 GHz applications is presented. The chosen substrate material is Rogers RT 5880, with a thickness of 1.6 mm, a relative permittivity of 2.2, and a loss tangent of 0.0009. Initially, a simple rectangular patch antenna is designed. To address the challenges of low gain and low radiation efficiency, two rectangular parasitic elements are introduced. These parasitic elements interact with the main radiator, resulting in improved gain and radiation efficiency. In the final step, an extended ground plane structure is adopted to further enhance return loss, radiation efficiency, and gain. The proposed antenna achieves a high gain of 13.10 dBi and a maximum radiation efficiency of 90% with a compact size of 13.6 × 10.6 mm2. For bandwidth calculations, given that the 60 GHz frequency band is known for its challenging propagation environment, the -15 dB criteria is chosen instead of the commonly used -10 dB criterion. According to this -15 dB criterion, the antenna exhibits wideband behavior spanning from 55 to 65 GHz, offering an impressive impedance bandwidth of 10 GHz. This design demonstrates significant potential for 60 GHz applications.

Cylindrical conformation and miniaturization of cavity-backed magnetoelectric antenna with an outer Γ-shaped probe

Abstract In this article, the cylindrical conformation of a linearly polarized cavity-backed magnetoelectric (ME) antenna is studied. Starting from a planar ME antenna presenting a wide bandwidth due to a specific design of its feeding probe, the impact of conformation is shown; the coupling between the ME dipole and the cavity walls is demonstrated to be the key element to keep a wideband behavior. Conformal antennas offering the same impedance bandwidth as the planar antenna are presented operating at Global Navigation Satellite System frequencies (1.164–1.61 GHz). As a result of the conformation, the antenna size has to be reduced to maintain the coupling and a wideband behavior. A prototype conformed to a 44-mm radius cylinder was built using low-cost additive manufacturing. External dimensions of 62 × 62 × 35 mm3 (0.285 × 0.285 × 0.16λ03, where λ0 is the wavelength at 1.38 GHz) were obtained, showing a ground plane area reduction of 46% compared to the planar antenna with the same materials. The conformal antenna also exhibits very steady radiation properties with a gain of around 4.5 dBi and a very similar and stable 3 dB beamwidth around 113° in E- and H-planes. A relatively good agreement is found between measurements and simulation.

Characterization of Instrument Transformers under Realistic Conditions: Impact of Single and Combined Influence Quantities on Their Wideband Behavior.

Instrument transformers (ITs) play a key role in electrical power systems, facilitating the accurate monitoring and measurement of electrical quantities. They are essential for measurement, protection, and metering in transmission and distribution grids and accurately reducing the grid voltage and current for low-voltage input instrumentation. With the increase in renewable energy sources, electronic converters, and electric vehicles connected to power grids, ITs now face challenging distorted conditions that differ from the nominal ones. The study presented in this paper is a collaborative work between national metrology institutes and universities that analyzes IT performance in measuring distorted voltages and currents in medium-voltage grids under realistic conditions. Both current and voltage measuring transformers are examined, considering influence quantities like the temperature, mechanical vibration, burden, adjacent phases, and proximity effects. The study provides detailed insights into measurement setups and procedures, and it quantifies potential errors arising from IT behavior in measuring distorted signals in the presence of the various considered influence quantities and their combinations. The main findings reveal that the temperature has the most evident impact on the inductive voltage transformer performance, as well as the burden, causing significant changes in ratio error and phase displacement at the lower temperatures. As for low-power ITs, establishing a priori the effects of adjacent phases and proximity on the frequency responses of low-power ITs is a complex matter, because of their different characteristics and construction solutions.

Analysis of overvoltages across line insulator strings considering the ground-wire and phase conductors corona

This paper assesses the influence of corona effect on the overvoltages developed across the insulator strings of overhead transmission lines due to lightning. The influence of corona is investigated considering lightning strikes to the tower top and shielding wires at midspan. A large range of soil resistivity and lightning currents peaks are evaluated in the analysis, and the stress across the insulator strings is evaluated applying the integration method. Simulations are carried out in the Alternative Transient Program (ATP/EMTP), wherein the corona effect is represented through the accurate Suliciu corona model, which was implemented using the MODELS interface and combined with J. Marti line model. Furthermore, it was also represented the wideband behavior of tower grounding system. Results showed that corona effect has a minor influence in the overvoltages across the insulator string for strikes to the tower top. However, it strongly influences the overvoltages across line insulators ensuing from a lightning strike to the shielding wire at the midspan, leading to a decrease in the peak value of the lightning current that causes line flashover.

3D-printed wideband reflectarray antennas with mechanical beam-steering

Abstract This paper investigates the performance of 3D-printed dielectric reflectarray antennas (RAs) with wideband behavior and beam-steering capabilities. The designed unit cell consists of a single-layer dielectric element perforated with a square hole, whose side is used to control the local variation of the reflection coefficient. The numerical analysis of the unit cell and of first $52\times52$ reflectarray working in Ka-band, whose scanning capabilities are tested just moving the feed along an arc, confirms that the unit cell has a stable behavior with respect to both the frequency and the direction of arrival of the incident field. In view of these promising capabilities, the proposed unit cell is used to design a bifocal reflectarray with the same size and working in the same frequency band of the first one. Its numerical characterization and the measurements of a prototype prove that the RA is able to provide less than 0.8 dB of gain losses over a scanning range of ±40∘ in the vertical plane, while the bandwidth varies between 13.5% and 28%, depending on the pointing direction. The obtained results demonstrate the effectiveness of the proposed approach and highlight the potential of 3D-printing technology for producing high performance, cost-effective RAs with wideband behavior and excellent beam-steering features.

Low-Temperature-Tolerant Strain-Sensing Flexible Composite for Soft Body Armor.

Developing soft body armor with sensing characteristics in various application scenarios is a challenge but important for creating a peaceful world and personal safety, whereas existing materials suffer from indefinite protective effects and stimulus response at subzero temperatures in the long term. Herein, an anti-freezing and flexible puncture-resistance composite with strain-sensing ability is developed by compounding a NaCl-soaked poly(vinyl alcohol) (PVA)/sodium alginate (SA)/glycerol (Gly) hydrogel (PSGN hydrogel) with Kevlar fabric. After freezing-thawing treatment once and NaCl immersion for 10 h, the Kevlar/PSGN-10 composite has excellent puncture-resistance properties and linear, rapid response, wide band, and stable strain-sensing behaviors at 25 and -30 °C. The composite's maximum puncturing force and energy dissipation at -30 °C are 53.92 N and 370 mJ, respectively, increased by 285 and 302% compared with neat Kevlar fabric. The flexibility reduction and the mass addition of the Kevlar/PSGN-10 composite are merely 19 and 40%, respectively, showing superior wearable comfortability and protection efficiency. The composites also reveal remarkable strain-sensing abilities at -30 °C (linear strain sensitivity with GF = 0.27 and R2 = 0.981, a wide working frequency range of 0.16-1.3 Hz, and sensing stability for 1500 cycles). Moreover, the composite could respond to multipart body motion directly, including fingers, elbows, wrists, and knees. Consequently, the Kevlar/PSGN composite developed in this paper is promising for intelligent soft body armor at various temperatures.

A left hand circularly polarized (LHCP) wideband antenna array based on artificial magnetic conductor for Ka-band applications

A left-hand circularly polarized (LHCP) 2 × 2 array antenna is presented based on a modified artificial magnetic conductor (AMC) with improved gain and side lobe levels (SLLs). A single port modified sequentially rotated feed network combines the four corner truncated patch elements to achieve wider impedance bandwidth and axial ratio (A.R) bandwidth. The AMC array having wideband behavior consists of 9 × 9 unit cells with a single unit cell size of 2.4 × 2.4 mm2. The particular AMC-surrounded antenna array is simulated and manufactured using Rogers RT Duroid/5880 substrate and provides a wider bandwidth covering Ka-band (27 GHz to 32 GHz). The dimensions of the AMC integrated antenna array are 30 × 30 × 0.508 mm3. The proposed AMC shows in-phase reflection behaviors between (+ 90 and − 90) degree, from 27 GHz to 32 GHz. Combining the four-element antenna array with the AMC reflector improved the gain level of 0.7 dBi, 2.9 dBi, and 2.5 dBi at 28 GHz, 29 GHz, and 30 GHz, respectively. The simulated s-parameter (S11) and radiation patterns results are experimentally verified by measuring the prototype of the recommended antenna model. The proposed antenna array shows a stable gain variation and directive radiation patterns along 0o with low side lobe levels. Based on the performance, the proposed AMC-based antenna array can be an effective choice for the 3 U satellite applications in Ka-band.

A Comparison of Surrogate Behavioral Models for Power Amplifier Linearization under High Sparse Data.

A good approximation to power amplifier (PA) behavioral modeling requires precise baseband models to mitigate nonlinearities. Since digital predistortion (DPD) is used to provide the PA linearization, a framework is necessary to validate the modeling figures of merit support under signal conditioning and transmission restrictions. A field-programmable gate array (FPGA)-based testbed is developed to measure the wide-band PA behavior using a single-carrier 64-quadrature amplitude modulation (QAM) multiplexed by orthogonal frequency-division multiplexing (OFDM) based on long-term evolution (LTE) as a stimulus, with different bandwidths signals. In the search to provide a heuristic target approach modeling, this paper introduces a feature extraction concept to find an appropriate complexity solution considering the high sparse data issue in amplitude to amplitude (AM-AM) and amplitude to phase AM-PM models extraction, whose penalties are associated with overfitting and hardware complexity in resulting functions. Thus, experimental results highlight the model performance for a high sparse data regime and are compared with a regression tree (RT), random forest (RF), and cubic-spline (CS) model accuracy capabilities for the signal conditioning to show a reliable validation, low-complexity, according to the peak-to-average power ratio (PAPR), complementary cumulative distribution function (CCDF), coefficients extraction, normalized mean square error (NMSE), and execution time figures of merit. The presented models provide a comparison with original data that aid to compare the dimension and robustness for each surrogate model where (i) machine learning (ML)-based and (ii) CS interpolate-based where high sparse data are present, NMSE between the CS interpolated based are also compared to demonstrate the efficacy in the prediction methods with lower convergence times and complexities.

A Compact, Low-Profile Shorted TM$_{1/2,0}$ Mode Planar Copolarized Microstrip Antenna for Full-Duplex Systems

In this letter, a single-layer compact copolarized shorted TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2,0</sub> mode microstrip patch antenna is presented for in-band full-duplex application. Two shorted TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2,0</sub> mode patch antennas, used for transmission and reception purposes, make the structure compact. The wideband behavior of the patch antenna is obtained by fusing the two resonances, one because of the shorted TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2,0</sub> mode radiating patch and the other because of the λ/4 line resonator. To enhance the isolation between the transmitter and receiver antenna, a novel defected ground structure is used. Slots are introduced into the ground plane to create a weak field region for the basic antenna element. The other antenna element (receiver) is located in the weak field region to enhance isolation. Further enhancement in isolation is achieved by introducing a T-shaped metallic strip into the slots. The structure is proposed with the credits of compactness, enhanced bandwidth, colinear polarization, very less fabrication complexity, low profile, and high isolation. The proposed structure is fabricated and measured. The structure experimentally exhibits a bandwidth (≤ −10 dB) of 2.42–2.52 GHz with the isolation of 25 dB, peak isolation of 36 dB, and an average realized gain of 4 dBi in the entire band.

Design of triangular shaped slotted patch antennas for both wideband and multiband applications

In this article two fractal geometry-based slotted patch antennas are designed to achieve wideband response with multiband characteristics and reduced cross polarized radiation in both E- and H-plane for all the resonating bands. The proposed antennas are fed with microstrip line feeding formed on a FR4 substrate of size 0.25𝜆0 × 0.25𝜆0 × 0.02𝜆0 mm3 and loaded with a partial ground plane at the bottom of the substrate. HFSS is used to design and simulate both the antennas. Wideband behavior and impedance matching of Antenna-1 are improved by optimizing the factor of iteration and length of the ground plane. Due to addition of 3 identical split ring resonators (SRR) with the antenna geometry leads to achieve multiband response in Antenna-2. The dimensions of the SRR connectors and feedline have been optimized through parametric analysis to match the impedance properly at all the three resonating bands. It has been found that simulated and measurement results of both the antennas are properly matched.

Wideband and High Gain Array Antenna for 5G Smart Phone Applications Using Frequency Selective Surface

This work presents an eight element array antenna with single layer frequency selective surface (FSS) to obtain high gain. The eight elements are fed by single port. The FSS consists of 14x6 unit cells with one unit cell size is 5&#x00D7;5 <i>mm</i>² having wideband behavior. The antenna uses Rogers RT Duroid 5880 substrate and giving very wide bandwidth from 20 GHz to 65 GHz, covering mm-wave 5G bands (including 28 GHz, 38 GHz and 60 GHz). The designed FSS is showing stop band transmission characteristics below -10 dB threshold from 25 GHz to 42 GHz and 59 GHz to 61 GHz. The eight element antenna integrated with the FSS reflector, which results an improvement in the gain level from 12 dB to 15 dB at 28 GHz, from 10 dB to 12 dB at 38 GHz, and from 9.5 to 11 dB at 60 GHz. The dimensions of the antenna are 33&#x00D7;27&#x00D7;0.787 <i>mm</i>³. The proposed antenna shows stable gain and directional radiation patterns. The simulation findings are experimentally confirmed, by testing the fabricated prototypes of the proposed antenna system.

Integrated Stacked Parallel Plate Shunt Capacitor for Millimeter-Wave Systems in Low-Cost Highly Integrated CMOS Technologies

This letter presents a stacked parallel plate (SPP) shunt capacitor (SC) that benefits from metal stack increment with process nodes advancement. It demonstrated high quality (Q) factor and high self-resonance frequency (SRF), promoting the design of analog integrated circuits (IC) in low-cost highly-integrated CMOS technologies at millimeter-wave (mm-wave) frequency range. As a proof-of-concept, an analytical-equation based design method is also proposed and three ac-grounded capacitors: 300-fF, 600-fF and 900-fF, are implemented in STMicroelectronics (STM) 55-nm process. Characterization is performed up to 100 GHz. An effective capacitance density of 0.8 fF/μm2 is obtained. Measurements show Q-values reaching up to 14.7 at 100 GHz and equivalent input series resistances with flat wide band behavior reaching at most an average of 0.55 Ω. SRFs of 140 GHz for the 900-fF SPP-SC up to 368 GHz for the 300-fF SPP-SC are also determined from measurements: the highest SRFs for such large capacitances to the authors’ knowledge.

Generation of Beam Tilt through Three-Dimensional Printed Surface

In this paper, 3D printed surfaces are presented to study this technology’s application in generating beam tilt for the electromagnetic waves in the Ku-band. Additionally, the input source is maintained by a feed horn that is additively manufactured and is coated with copper spray paint to add conductivity, which is fed by a WR-75 waveguide. The proposed beam tilt generating surface is also referred to as a Beam Deviating Surface (BDS). There is no relative gap between the BDS and the aperture of the horn, which eventually decreased the overall antenna height. The BDS layer is able to deviate the beam for a fixed elevation angle of 22.5∘ and could be consequently rotated along with the rotation of the BDS prototype. The voltage standing wave ratio value is less than two over the operating frequency range, which depicts the wideband behavior. The measured and simulated radiation patterns show that we can tilt the electromagnetic waves in ranges of up to +/−22.5∘ with a minimum side lobe level of −5 dB at frequencies from 10 to 15 GHz. This signifies the wideband characteristic of the proposed prototype, which is achieved by Vero material from Multijet Printing that is a low-cost and rapid manufacturing 3D printing technology.

Design and Modeling of Wideband Planar Antennas Using Characteristics Modes

Origin of wideband nature and radiation behavior in many broadband antenna structures is not clearly understood. In this article, we have attempted to clarify those phenomena using characteristic mode (CM) analysis along with equivalent circuit (EC) modeling. By modeling the modal impedance of antenna for a large bandwidth, considering natural resonances and anti-resonances, the EC models are developed for various wideband antennas. It is observed that the reactive loading and resonant mode coupling effects are largely contributing in the formation of wideband and far fields of antenna. These models can be used in SPICE simulators to study the effective communication between wireless transmitter and receiver systems without an EM solver. A novel design method is proposed on the development of wideband antennas using a modal impedance model and coupled mode theory of resonant modes. This method yields accurate design to achieve desired center frequency and bandwidth using structural modifications.

Rapid Prototyping of Bio-Inspired Dielectric Resonator Antennas for Sub-6 GHz Applications.

Bio-inspired Dielectric Resonator Antennas (DRAs) are engaging more and more attention from the scientific community due to their exceptional wideband characteristic, which is especially desirable for the implementation of 5G communications. Nonetheless, since these antennas exhibit peculiar geometries in their micro-features, high dimensional accuracy must be accomplished via the selection of the most suitable fabrication process. In this study, the challenges to the manufacturing process presented by the wideband Spiral shell Dielectric Resonator Antenna (SsDRA), based on the Gielis superformula, are addressed. Three prototypes, made of three different photopolymer resins, were manufactured by bottom-up micro-Stereolithography (SLA). This process allows to cope with SsDRA’s fabrication criticalities, especially concerning the wavy features characterizing the thin spiral surface and the micro-features located in close proximity to the spiral origin. The assembly of the SsDRAs with a ground plane and feed probe was also accurately managed in order to guarantee reliable and repeatable measurements. The scattering parameter S11 trends were then measured by means of a Vector Network Analyzer, while the realized gains and 3D radiation diagrams were measured in the anechoic chamber. The experimental results show that all SsDRAs display relevant wideband behavior of 2 GHz at −10 dB in the sub-6 GHz range.

Modified Koch Fractal Antenna for Multi and Wideband Wireless Applications

This paper focuses on the design and development of modified Koch fractal antenna. Compared to traditional Koch curve antenna, the presented antenna possesses a greater number of frequency bands and better impedance matching. Furthermore, the bacterial foraging optimization (BFO) approach is implemented to enhance the impedance bandwidth. The developed technique has been verified by employing various numerical simulations. The design parameters generated from the optimization procedure have been utilized to manufacture the antenna and the respective experimental and simulated results compared. The measured results show that the designed antenna exhibits multi and wideband behavior, covering WLAN, WIMAX, and various other wireless applications.

A wideband 0.9–2.4 GHz 25 W high‐efficiency Gallium Nitride radio frequency power amplifier

AbstractIn this work, a 0.9–2.4 GHz, 25 W output power, radio frequency (RF) power amplifier based on Class‐E switchmode topology has been analyzed. A load‐pull simulation method is used to optimize the power performance in the operating band. To design input and output matching networks an optimized low pass filter network was used. Simulated results of the power amplifier (PA) demonstrate wideband behavior which covers a 0.9–2.4 GHz band with an efficiency of 25%–78%, an output power of 25 W (44 dBm), and an average gain of 17 dB. The designed PA provides attractive features associated with a wider band, high gain, and efficiency, which makes it a proper candidate for the mobile transmitter and cellular infrastructure applications.

Design of Substrate-Integrated Dielectric Resonator Antenna With Dielectric Vias

For the first time, dielectric vias were used to design a substrate-integrated dielectric resonator antenna (SIDRA). The dielectric vias consist of cylindrical holes drilled into the PCB substrate and filled with presintered nanoparticles of barium strontium titanate (BST). The BST nanoparticles were found to have a dielectric constant of 20, with an approximate loss tangent of ~0.05. The dielectric-vias loaded substrate constitutes an effective medium for the DRA design. The dielectric vias are arranged in a concentric manner around a core substrate material region, giving a wideband multiring SIDRA. It was found that the wideband behavior is due to two different dielectric resonator modes, namely, the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ11</sub> mode and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ31</sub> half-mode. The TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ31</sub> half-mode is a modified version of the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ31</sub> -mode of a regular dielectric resonator and is reported here for the first time. The measured and simulated -10-dB impedance bandwidths of the DRA are 33.4% and 35.8%, respectively.

Parametric Analysis of an Optical Log-Spiral Nano-Antenna for Infrared Energy Harvesting

In this paper, we present the design of a spiral nano-antenna dedicated to infrared energy harvesting at 28.3 THz. A comprehensive, detailed parametric study of key parameters such as the initial angle at the origin arm, width of the spiral arms, gap between the two arms, thickness of substrate, length of substrate, thickness of patch and number of turns of the nano-antenna is also presented and discussed in order to harvest maximum electric field in the gap of the spiral antenna in the frequency range of 28 – 29 THz. The maximum electric field is simulated at 28.1, 28.3, 28.5 and 28.7 THz. A variation of the electric field of the antenna for different value of incident wave angle at the resonance frequency 28.3 THz has been simulated. The main advantages of the studied structure are its ability to reach high confined electric field within its gap, its wideband behavior around the operating frequency 28.3 THz, and its insensitivity to polarization of incident electromagnetic waves.