High Impedance Surface Research Articles

Reduced size, UWB AMC-backed bow-tie antenna compatible with EMI sensor for subsurface impulse radars

Low-profile, wideband, and electromagnetic induction (EMI) sensor-compatible antenna for ground penetrating impulse radar applications is an indispensable need for humanitarian demining operations. We present an ultra wideband (UWB), small-size AMC-backed fat bow-tie antenna for such detection systems. Fat bow-tie has longitudinal slots along its main polarization axis so that Eddy currents due to the EMI sensor are minimized on the antenna. Unlike discrete element or tapered reactive/resistive loading, high-impedance surface material is placed inside the cavity to increase the bandwidth and to decrease the ringing caused by the cavity. The proposed antenna has a directional radiation pattern and operates between 700 MHz and 3.2 GHz.

A shared-aperture pentaband antenna with high impedance surface for CubeSat application

A circular polarized (CP) pentaband antenna based on the aperture-in-aperture (AIA) concept is presented for CubeSat applications. This AIA consists of five different bands ranging from L-band to Ka-band. Four different antennas, each operating at a specific frequency band, namely 12 GHz, 18.5 GHz, 26 GHz, and 32 GHz, were incorporated into an L-band (viz. 1.5 GHz) antenna. Notably, the five antennas can operate simultaneously for a CubeSat downlink operation with a frequency ratio of 21.3:1. The antenna structure shows a realized gain of 5–10 dBi with good CP bandwidth (< 3 dB) across the overall operational frequency range. That is, the realized gain of L-band (1.5 GHz), X-band (12.5 GHz), K-band1 (18.5 GHz), K-band2 (26 GHz), and Ka-bands (32 GHz) are 5.05 dBi, 8.21 dBi, 7.33 dBi, 7.97 dBi, and 8.56 dBi. A high impedance surface (HIS) is incorporated with the Ka-band antenna to mitigate the ripples in the radiation pattern created by the interference of surface waves. A prototype was fabricated and tested. The measurement data agrees well with the simulation.

Modal analysis and higher order mode suppression of a high impedance surface-based bowtie antenna

Abstract The present work studies the design of a high impedance surface (HIS)-based bowtie antenna in the framework of characteristic mode analysis (CMA) and proposes the method of higher order mode suppression. A triangular-elliptical bowtie antenna operating in the frequency range of 1.6–6 GHz is designed. The radiating and higher order modes of the proposed antenna are identified using CMA, and an HIS structure is used to enhance the desired mode and to suppress the higher order mode in order to get high gain, good front-to-back ratio (FBR), and stable radiation characteristics. The final designed HIS-based bowtie antenna gives stable radiation patterns from 1.7 to 5.5 GHz with a maximum boresight gain of 10.5 dB. Also, gain from 6.5 to 12 dB and FBR from 8 to 18 dB are obtained in the operating bandwidth. The proposed antenna features the advantages of low profile, wideband and high boresight gain making it suitable for ground-penetrating radar applications.

Analytical and numerical study of properties surfaces with high impedance

Original high-impedance surface (HIS) is studied in this paper. Analytical and numerical (using Ansoft HFSS package) research was done for this structure. It is demonstrated that this structure illuminated by plane wave operates as HIS with wide resonant band. Moreover effective magnetic permeability of the structure under study is calculated.

Application of high-impedance surfaces for low-profile antennas

The fundamental properties of high-impedance surfaces (Sievenpiper’s structures) in low-profile and miniature antenna design are considered. The analysis of the geometry and electric parameters influence on direction characteristics and input-match is given.

A low-profile metamaterial absorber with ultrawideband reflectionless and wide-angular stability

An ultrawideband reflectionless metamaterial absorber (MA) is proposed by replacing the metallic ground with the complementary split-ring resonator (CSRR) structure. The proposed MA exhibits −10 dB reflectivity spectrum from 1 GHz to 20 GHz, which maintains more than 90% absorption from 1.5 GHz to 20 GHz. Furthermore, it achieves angle stability for TE and TM polarization at oblique incident angles up to 40° and 65°, respectively. To achieve broadband absorption spectrum, we have adopted a single-layer high-impedance surface (HIS) loaded with a double-layer magnetic material (MM) structure. To further realize the RCS reduction into a lower frequency range, we have employed the scattering cancellation technology into the traditional metallic ground. Finally, we have fabricated a sample exhibiting the 10 dB RCS reduction from 1 GHz to 20 GHz with a thickness of 10 mm. Measurement and simulation results confirm that the proposed MA exhibits excellent comprehensive performance, making it suitable for many practical applications.

Planar Antenna Design on the Characteristics of Moore Fractal-based High Impedance Surface

This work presents a planar antenna with a rectangular shape designed over a Moore curve fractal-shaped High Impedance Surface (HIS). The Moore fractal geometries are space-filling curves and are useful for multiband applications. The Moore curve-shaped fractal HIS is simulated up to three iterations, and performance is examined. The proposed antenna has multiband operation within the S-band, C-band, and lower X-band frequency of operation. The antenna has a peak gain of 5.08 dB, 4.69 dB, and 5.07 dB with a Moore curve fractal HIS, with iterations 1, 2, and 3 used as the ground plane. The antenna has been analyzed regarding the reflection coefficient, radiation pattern, 3-D polar plots, and surface current distribution. With Moore curve iteration 1, a shaped HIS provides a maximum bandwidth of 740 MHz with the center frequency of 10.95 GHz, 1.24 GHz with the center frequency of 10.57 GHz, and 1.09 GHz with the center frequency of 12.5 GHz with the second and third iterations, respectively.

Extremely Wideband Metamaterial Absorber Using Spatial Lossy Transmission Lines and Resistively Loaded High Impedance Surface

In this article, the design, principle, and characterization of a 3-D metamaterial absorber (MA) have been presented, which consists of the spatial lossy transmission lines (SLTLs) and the resistively loaded high impedance surface (HIS). The proposed MA possesses a fractional bandwidth of 193% with absorption rate of above 90% in the frequency range from 2 to 110 GHz under TM polarization while maintaining large oblique incident angle stability of over 50 <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> . For demonstration, a prototype is fabricated, whose measurement results are in good agreement with the simulation results. Losses from the periodically patterned SLTLs and resistively loaded HIS are introduced by resistive graphene films using screen-printing technology, resulting in avoiding conventional soldering of numerous lumped resistors. An equivalent circuit model and a surface loss distribution are given to better illustrate the physical mechanism. Our findings establish general and systematic strategies for guiding the design of extremely wideband MA with large incident angle and pave the way for enhancing the microwave performance in applications of electromagnetic compatibility, imaging, radar detection, and stealth.

Metasurface Antenna for Fast Frequency Scanning With Application to Conical Direction Finding

The functionality of a metadome to provide fast frequency conical beam scanning using a simple feeding, is reported in this letter. A metasurface composed by periodic patches covering a simple monopole antenna, acts as a partially reflective sheet to produce frequency-scanned conical beams. Then, the addition of a high impedance surface in the ground plane, is used to increase the scanning ratio. This is important to cover a wide scanning range using a narrow frequency bandwidth. A design example for conical direction finding with a field of view of 60 degrees and using the 200 MHz unlicensed band from 5.1 GHz to 5.3 GHz, is demonstrated with a metadome antenna prototype.

Design and Analysis of Fractal-Shaped High-Impedance Surface Unit Cell Characteristics

Fractal geometries consistently provide solutions to several electromagnetic design problems. In this paper, fractal geometries such as Hilbert and Moore curves are used to design efficient High-Impedance Surfaces. Modern communication devices have many sensors that are needed to communicate wirelessly. The critical component of wireless communications is antennas. Planar microstrip patch antennas are popular due to their low profile, compactness, and good radiation characteristics. The structural disadvantages of microstrip antennas are that they have surface waves that propagate over the ground plane. High-Impedance Surface (HIS) planes are a prominent solution to minimize and eliminate surface waves. The HIS structures behave as active LC filters that suppress surface waves at their resonance frequency. The resonance frequency of the structure is obtained by its LC equivalent or by analyzing the reflection phase characteristics. This work presents conventional HIS structures similar to mushroom HIS and fractal HIS such as Hilbert curve and Moore curve HIS. The HIS reflection phase characteristics are obtained by applying periodic boundary conditions with plane wave illumination. The results were obtained in terms of the reflection phase angle. The conventional mushroom structures show narrow band characteristics at given dimensions of 10 mm × 10 mm and 20 mm × 20 mm. These structures are helpful in the replacement of PEC ground planes for patch antennas under sub-6 GHz. The Hilbert and Moore fractals are also designed and have a multiband response that can be useful for L, S, and C band applications. Another design challenge of HIS is protrusions, which make design difficult. The work also presents the effect of having vias and the absence of vias on reflection phase characteristics. The response shows the least and no significant effect of vias under the x-band operation.

The March 1940 Superstorm: Geoelectromagnetic Hazards and Impacts on American Communication and Power Systems

AbstractAn analysis is made of geophysical records of the 24 March 1940, magnetic storm and related reports of interference on long‐line communication and power systems across the contiguous United States and, to a lesser extent, Canada. Most long‐line system interference occurred during local daytime, after the second of two storm sudden commencements and during the early part of the storm's main phase. The high degree of system interference experienced during this storm is inferred to have been due to unusually large‐amplitude and unusually rapid geomagnetic field variation, possibly driven by interacting interplanetary coronal‐mass ejections. Geomagnetic field variation, in turn, induced geoelectric fields in the electrically conducting solid Earth, establishing large potential differences (voltages) between grounding points at communication depots and transformer substations connected by long transmission lines. It is shown that March 1940 storm‐time communication‐ and power‐system interference was primarily experienced over regions of high electromagnetic surface impedance, mainly in the upper Midwest and eastern United States. Potential differences measured on several grounded long lines during the storm exceeded 1‐min resolution voltages that would have been induced by the March 1989 storm. In some places, voltages exceeded American electric‐power‐industry benchmarks. It is concluded that the March 1940 magnetic storm was unusually effective at inducing geoelectric fields. Although modern communication systems are now much less dependent on long electrically conducting transmission lines, modern electric‐power‐transmission systems are more dependent on such lines, and they, thus, might experience interference with the future occurrence of a storm as effective as that of March 1940.

Millimeter wave array-HIS antenna for imaging applications

The combination of a patch array antenna with a High Impedance Surface (HIS) metasurface at mmWave frequencies has been studied. The antenna is intended for a collision avoidance imaging application, which will help blind or visually impaired people in their daily lives. A compact and cost-effective uniplanar design, operating in the mmWave unlicensed frequency band (24.05–24.25 GHz), has been reached. Multiple arrangements and dispositions of the HIS unit-cells with the array have been explored in order to improve the radiation parameters of the basic design. Both, the basic array and the array-HIS combination, have been manufactured using laser micromachining. Prototypes have been measured in an anechoic chamber and measurement results have been confronted with the simulation ones in terms of bandwidth and radiation properties. A comparison with the state-of-the-art antennas at 24 GHz has been performed to endorse the achievements of this work.

Multi-Layer Beam Scanning Leaky Wave Antenna for Remote Vital Signs Detection at 60 GHz.

A multi-layer beam-scanning leaky wave antenna (LWA) for remote vital sign monitoring (RVSM) at 60 GHz using a single-tone continuous-wave (CW) Doppler radar has been developed in a typical dynamic environment. The antenna's components are: a partially reflecting surface (PRS), high-impedance surfaces (HISs), and a plain dielectric slab. A dipole antenna works as a source together with these elements to produce a gain of 24 dBi, a frequency beam scanning range of 30°, and precise remote vital sign monitoring (RVSM) up to 4 m across the operating frequency range (58-66 GHz). The antenna requirements for the DR are summarised in a typical dynamic scenario where a patient is to have continuous monitoring remotely, while sleeping. During the continuous health monitoring process, the patient has the freedom to move up to one meter away from the fixed sensor position.The proposed multi-layer LWA system was placed at a distance of 2 m and 4 m from the test subject to confirm the suitability of the developed antenna for dynamic RVSM applications. A proper setting of the operating frequency range (58 to 66 GHz) enabled the detection of both heart beats and respiration rates of the subject within a 30° angular range.

A Wideband Dual-Circularly Polarized, Simultaneous Transmit and Receive (STAR) Antenna Array for Integrated Sensing and Communication in IoT

This article presents a novel 5.8-GHz ISM-band dual-circularly polarized (CP) simultaneous transmit and receive (STAR) common-aperture antenna array (CAAA) for integrated sensing and communication (ISAC) in Internet of Things (IoT). A new near-field cancellation technique based on differential feeding and geometrical symmetry is proposed for dual-CP to realize high TX/RX isolation. In addition, a high-impedance surface is introduced to further improve the TX/RX isolation. Furthermore, the parasitic patches are added to enhance the gain and isolation bandwidth (BW). The simulation results demonstrate that the proposed CAAA possesses the merits of high isolation (up to 67 dB), wide isolation BW (better than 40 dB for 240 MHz BW), high gains (up to 10/10.5 dB for right-hand CP (RHCP)/left-hand CP (LHCP)), wide 1-dB gain BWs (better than 230/350 MHz BW for RHCP/LHCP), and low-axial ratios (lower than 1.4 dB). The designed CAAAs are fully characterized and the experimental results meet the simulation very well. For the first time, systematic validations for both wireless communication and radar sensing have been thoroughly carried out by integrating the proposed CAAA in the custom-designed full-duplex radio system. The experimental results not only prove the validity of the design methodology but also the feasibility of employing the proposed CAAA for ISAC, which indicates potential applications in IoT era.

An Ultra‐Broadband Chirality Selective Metastructure Absorber using High Impedance Surface

AbstractIn this paper, an ultra‐wideband chirality selective metastructure absorber is proposed that enables differential absorption and reflection of circularly polarized waves in the terahertz (THz) range. The structure achieves circular dichroism (CD) by using asymmetrically split metal rings as fundamental meta‐atoms. Most critically, the high impedance surface and air‐resonant cavities are inserted separately in the meta‐atoms and dielectric substrate to enhance CD and broaden the bandwidth of absorption. The metastructure absorber can achieve more than 90% absorption of right circularly polarized waves at 0.675–1.244 THz, and it can maintain more than 90% reflection of left circularly polarized waves at 0.607–1.229 THz without changing the direction of rotation. Besides, its CD can reach more than 80% at 0.687–1.213 THz with a relative bandwidth of 55.3%. Spin‐selective absorption, which is closely related to breaking chiral symmetry, is investigated through power loss distribution, wide‐angle incidence, and scan parameter optimization. The proposed strategy is further validated in the THz band, and the polarization selection and manipulation techniques can be applied to chiral sensing/radio‐thermometry, circular polarization detectors/lasers, and molecular spectroscopy.

A continuous frequency tuning Fabry–Perot Cavity antenna with stable radiation performance

AbstractThis paper presents a continuous frequency tuning Fabry–Perot Cavity (FPC) antenna of which the operating frequency can be varied from 4.87 to 5.84 GHz (18.1%). The cavity of the proposed antenna is excited by a double-layer antenna structure, which is made up of a main square patch and a parasitic one. The superstrate is a frequency-selective surface, consisting of 6 × 6 square-patch-type unit cells. The frequency tuning property is realized by employing 48 phase-changing elements placed around the main patch, which forms a reconfigurable high impedance surface (HIS). By controlling the biasing voltages of the varactors inserted in the HIS element, its capacitances and reflection phases can be varied continuously, which leads to a variation of the operating frequency. An antenna prototype has been fabricated and measured for validation. The measured results are in good agreement with the simulated ones. In the frequency tuning range, the measured realized gains have a smaller variation from 10.2 to 14.1 dBi compared with other reported frequency tuning FPC antennas.

Design of Rectangular Patch Antenna on the Hilbert Fractal-shaped High Impedance Surface

The high Impedance Technique has emerged as a modern approach for high-gain microstrip antennas. A high impedance surface minimizes surface waves and provides increased gain. Instead of, a typical mushroom to design High Impedance Surface (HIS), fractal geometry can be used. Hilbert curve-based Fractal geometry minimizes physical length and keeps electrical length the same. In this work, three iterations of Hilbert curve-shaped HIS geometry are studied with emphasis on HIS application. Fractal facilitates multi-frequency operation from GSM 1800 MHz to 6 GHz Wireless applications. The antennas have a peak gain of 5.3 dbi. The simulation is conducted in HFSS, and the analysis is performed using reports like reflection coefficients, radiation patterns, and gain plots

High Impedance Fault Location Methods: Review and Harmonic Selection-Based Analysis

High Impedance Faults (HIFs) are recurring events in electrical Distribution Systems (DSs) and occur by the contact between energized conductors and high impedance surfaces. HIFs may pose hazards to living beings and cause bushfires. However, the HIF protection has not been completely solved due to the small fault current and varying impedance, inhibiting traditional protection techniques from functioning correctly. In the literature, researchers have mainly focused on detection techniques. Thus, the development of HIF Location Methods (HIFLMs) is recent, and evidences for conclusive solutions are still lacking. Moreover, to this date, no existing study reviews the main challenges concerning HIFLMs in DSs. This paper proposes a systematic analysis of the common stages to design the main existing HIFLMs. The strategy is evaluating the similar characteristics that pose a common research path regarding challenges faced in real-world conditions. Additionally, this paper proposes a case study to assess the best input signals, metrics, and machine learning-based decision algorithms of a new HIFLM. The results are promising, with high identification rates, even in noisy conditions. The methodology can help to select the datasets for supervised learning-based HIFLM. Highlighting the state-of-art of current methods and support development of HIFLMs are this paper’s main contributions.

Spectrally stable thermal emitters enabled by material-based high-impedance surfaces.

Radiative thermal engineering with subwavelength metallic bodies is a key element for heat and energy management applications, communication and sensing. Here, we numerically and experimentally demonstrate metallic thermal emitters with narrowband but extremely stable emission spectra, whose resonant frequency does not shift with changes on the nanofilm thickness, the angle of observation and/or polarization. Our devices are based on epsilon-near-zero (ENZ) substrates acting as material-based high-impedance substrates. They do not require from complex nanofabrication processes, thus being compatible with large-area and low-cost applications.

3D printed lightweight metastructure with microwave absorption and mechanical resistance

Recently, lightweight multifunctional metastructures have attracted significant attention owing to its advantage of integrating microwave absorption and mechanical resistance. However, these features are typically entangled, and a feasible strategy for independently manipulating the microwave absorption and mechanical resistance is still lacking. Herein, a double high-impedance surface-loaded honeycomb (DHHC) is proposed, based on a theoretical analysis, and fabricated using a 3D printing technique. The impedance and surface current distribution of the DHHC were analyzed and investigated to achieve broadband microwave absorption characteristics. The structural parameters and resistances of the high-impedance surface were investigated and optimized to regulate the absorbing bandwidth and reflectivity intensity. Our experimental results indicated that a 4.25 mm thick DHHC metastructure can achieve a –10 dB absorbing bandwidth at a frequency range of 6.73–18 GHz, as well as a –15 dB absorbing band at 8.42–14.75 GHz. Moreover, the structural parameters of the honeycombs were investigated for the adjustment of stress distributions during the compression and flexural processes. Load-bearing tests indicated that the DHHC possessed a mechanical resistance with an equivalent areal density of 2.32 kg/m2. This study provides a promising route for achieving independently manipulated compatibility between microwave absorption and mechanical resistance for practical applications.