Artificial Magnetic Conductor Structure Research Articles

In-band dual-polarization RCS reduction of waveguide slot array antenna integrated with AMC and PEC chessboard structure

An in-band low radar cross section (RCS) waveguide slot array antenna (WSAA) is proposed by using a chessboard structure composed of artificial magnetic conductor (AMC) and perfect electric conductor (PEC), which serves as the antenna radiator. The method for RCS reduction is the reflection energy cancellation. Standing wave array is used to achieve higher energy efficiency and more compact antenna structure. Experimental results show that the in-band monostatic RCS is sufficiently reduced with the chessboard structure application for both co- and cross-polarized incident waves, where 10-dB RCS compression is realized among the frequency range of 9.7–9.91 GHz for co-polarization and 9.5–9.85 GHz for cross-polarization with maximum RCS reductions of −13.3 dB and −11.9 dB, respectively. Meanwhile, the designed WSAA maintains the high gain characteristics of the original WSAA. The paper provides a simple, practical and effective strategy for stable RCS compression in the operation band of waveguide antenna array, which has potential applications in stealth platforms.

A high gain and high radiation efficiency optical transparent Fabry–Perot cavity antenna

AbstractThis letter proposes a novel high gain, high efficiency optically transparent Fabry–Perot Cavity antenna operating in millimetre‐wave. The antenna employs dual layers of transparent partially reflective surface and a transparent artificial magnetic conductor structure to enhance the gain and gain bandwidth. The reflection amplitude and phase have a low sensitivity to the sheet resistance of the transparent materials, which greatly reduce the requirement for the conductivity of transparent material and simplify the manufacturing process. The size of the antenna is 3.47λ0 × 3.47λ0 × 0.68λ0. A peak gain of 14.2 dBi, peak radiation efficiency of 67.1% and optical transparency of 81% are achieved.

A Compact and Robust RFID Tag Based on an AMC Structure.

A platform-tolerant RFID (Radio-Frequency Identification) tag is presented, designed to operate across the entire RFID band. This tag utilizes a small Artificial Magnetic Conductor (AMC) structure as a shielding element for an ungrounded RFID tag antenna. It can be easily mounted on various surfaces, including low permittivity dielectric materials, metal objects, or even attached to the human body for wearable applications. The key features of this RFID tag include its ability to be tuned within the worldwide RFID band, achieving a maximum theoretical read range of over 11 m. Despite its advanced capabilities, the design emphasizes simplicity and cost-effective manufacturing. The design and simulations were conducted using CST Studio Suite.

A Dual-Polarization Broadband Coupling Feed Dipole Antenna Based on Artificial Magnetic Conductor

A dual-polarized broadband coupled feed dipole antenna loaded with artificial magnetic conductor (AMC) structure is proposed. The proposed AMC structure with 4×4 elements shown in this paper consists of four perfect electrical conductor (PEC) rectangular strips and a ring to reduce the profile height of the dual-polarized dipole antenna. In addition, the dual-polarization antenna adopts coupling feed microstrip to excite two pairs of bow-tie patch. The overall size of the coupling feed dipole antenna is 1.1λ0×1.1λ0×0.09λ0 at 5.5 GHz. Measured results shows that the proposed dual-polarization antenna loaded AMC exhibit a 25.2% common working bandwidth (4.75-6.12 GHz). The isolation is less than -14 dB, and the peak gain is 10.6 dBi. This dipole antenna with AMC structure has the virtues of low profile, wide band, and good radiation performance and it has the potential to be used in C-band communication.

Enhancement of off-body communications with a low-SAR, high-gain multiband patch antenna designed with a quad-band artificial magnetic conductor

Abstract The increasing demand for wireless communication has emphasized the need for multiband antennas. This study presents a novel design for a multiband antenna with reduced specific absorption rate (SAR), high gain, and improved front-to-back ratio (FBR) achieved through the integration with a 4 × 4 artificial magnetic conductor (AMC) surface. The proposed antenna covers a wide range of wireless frequency bands, including Industrial, Scientific, and Medical, Wireless Local Area Network, Worldwide Interoperability for Microwave Access, Wi-Fi 6E, and 7, with resonating frequencies at 2.4, 3.2, 5.5, 7.5, and 10 GHz. The AMC unit cell creates four zero-degree reflection phases with double negative properties at 2.5, 3.8, 5.5, and 7.5 GHz. The compact design measures 0.23λ0 × 0.296λ0 × 0.0128λ0 and placed 0.104λ0 above an AMC surface of size 0.512λ0 × 0.512λ0 × 0.1296λ0. This structure enhances the gain by up to 8.55dBi at 6.01 GHz. The proposed antenna has −10 dB impedance bandwidth for these corresponding frequencies viz 2.34–2.43 GHz (3.77%), 2.81–3.83 GHz (30.72%), 4.82–6.21 GHz (25.20%), 7–7.65 GHz (8.87%), and 8.06–10.31 GHz (24.5%). An overall average percentage reduction value of SAR taken at these frequencies has been found to be 96.11% with AMC structure. The antenna sample was successfully fabricated, and the experimental results have been found to match well with the simulation results. This integrated design offers a promising solution for wearable off-body communication devices.

One hundred fifty GHz folded dipole antenna‐on‐chip based on artificial magnetic conductor structure

AbstractA folded dipole antenna using an artificial magnetic conductor (AMC) structure is proposed to improve the frequency bandwidth and reduce the size of the antenna on a chip. To change the distribution of the electromagnetic (EM) field, the proposed AMC structure shaped with square‐in‐square rings (SSRs) is arranged along the radiating metal of the folded dipole antenna and implemented on the lowermost metal layer of the backend oxide layers (BEOLs) between the radiating metal of the top layer of the BEOL and the ground plane of the bottom of the substrate. The SSR of the proposed antenna‐on‐chip (AoC) widens the frequency bandwidth by varying the electrical length to the ground and reduces the physical size of the radiating metal by increasing the effective permittivity. The 3D EM‐wave simulation shows that the proposed AMC structure changes the distribution of EM‐wave in the BEOL and Si substrate such that more EM fields are condensed around the radiating metal and the electrical length to the ground is nonuniform and longer. The AoC with the proposed AMC structure was fabricated using a 65‐nm standard complementary metal‐oxide semiconductor process with one‐poly and nine‐metal. Compared with the conventional 150‐GHz antenna that was implemented on the same die, the proposed differential antenna was measured to be a −10 dB bandwidth of 46 GHz, with a 1.12‐times improvement, and a size reduction of 20.4%. The measured gain of the proposed antenna was −5.99 dBi including the passive balun with an insertion loss of −1.36 dB in simulation.

A Low-Profile Wideband Patch Antenna With Modified Parasitic Mushroom Structures on Nonperiodic AMC

In this letter, a low-profile wideband antenna working around 28 GHz based on the nonperiodic artificial magnetic conductor (AMC) is presented. Mushroom structures are loaded with central patch to broaden bandwidth. Four vias at edges are added to suppress cross polarization. A parasitically coupled structure is integrated with AMC. The nonperiodic AMC, central patch, and parasitic structures create five resonant modes together. Characteristic mode analysis and effective relative permittivity of AMC are calculated to explain the bandwidth broadening mechanism. A prototype is fabricated to verify the design concept. The measured result shows wide impedance bandwidth of 33% (24.05–33.52 GHz) and high peak gain of 10.24 dBi.

Antenna Performance Enhancement using AMC Structure for 5G Frequency Range

This paper presents a microstrip patch antenna operated at the fifth generation (5G) frequency range, which is at 3.5 GHz. To enhance the performance of the proposed antenna, an Artificial Magnetic Conductor (AMC) structure is implemented into the design. The 1x3 AMC is sandwiched between two FR-4 substrates and the performance of the proposed antenna is compared with the antenna without AMC structure. The simulated results prove that the proposed antenna offers better reflection coefficient with -50.45 dB compared to only -15.55 dB for the conventional antenna. Wider bandwidth is also achieved with 427 MHz of frequency bandwidth as opposed to only 135 MHz for the antenna without AMC. Besides that, the integration of AMC enhances the gain of the antenna when 3.7 dBi is achieved in contrast to only 3.21 dBi for the conventional antenna. Moreover, the efficiency of the antenna with AMC is also improved up to 68.54%. Furthermore, the ability to shrink 52.23% of the size of the antenna without AMC making it very favorable to be applied in 5G bands.

Artificial Magnetic Conductor as Planar Antenna for 5G Evolution

A 5G wireless system requests a high-performance compact antenna device. This research work aims to report the characterization and verification of the artificial magnetic conductor (AMC) metamaterial for a high-gain planar antenna. The configuration is formed by a double-side structure on an intrinsic dielectric slab. The 2-D periodic pattern as an impedance surface is mounted on the top surface, whereas at the bottom surface the ground plane with an inductive narrow aperture source is embedded. The characteristic of the resonant transmission is illustrated based on the electromagnetic virtual object of the AMC resonant structure to reveal the unique property of a magnetic material response. The characteristics of the AMC metamaterial and the planar antenna synthesis are investigated and verified by experiment using a low-cost FR4 dielectric material. The directional antenna gain is obviously enhanced by guiding a primary field radiation. The loss effect in a dielectric slab is essentially studied having an influence on antenna radiation. The verification shows a peak of the antenna gain around 9.7 dB at broadside which is improved by 6.2 dB in comparison with the primary aperture antenna without the AMC structure. The thin antenna profile of λ/37.5 is achieved at 10 GHz for 5G evolution. The emission property in an AMC structure herein contributes to the development of a low-profile and high-gain planar antenna for a compact wireless component.

AMC-Based Low-Profile Dual-Band Slotted Patch Antenna for IoT Devices in the Healthcare System

An artificial magnetic conductor (AMC)-based patch antenna with a low profile is developed for wireless devices in IoT-based healthcare systems. The proposed antenna comprises two pairs of circular-shaped patches with circular-shaped slots and a dual-band 4 × 4 array of AMC reflectors with two zero-degree reflection responses to enhance the antenna's radiation performance. For the 2.45 GHz ISM and 5.4 GHz WLAN bands, the patch antenna has dimensions of 0.44λ0 × 0.52λ0 × 0.013λ0, with partial ground structures to improve radiation characteristics. Following that, a unique dual-band symmetrical AMC unit cell with dimensions of 22 × 22 × 1.6 mm3 is developed. There is a gap of 15 mm between the antenna and the AMC surface. The antenna is supported by a 4 × 4 AMC array that has a total dimension of 0.72λ0 × 0.72λ0 × 0.15λ0. The reflection coefficient values of less than − 10 dB in the 1.7–2.5 and 5.1–5.6 GHz bands, with a bandwidth percentage of 38 and 9.3%, respectively. The antenna's gains were 7.2 and 4 dBi inside the bands. Furthermore, the Specific Absorption Rate (SAR) value did not match the WHO's safety and health guidelines. The issue was solved by including an AMC surface in the proposed antenna. At 2.45 and 5.4 GHz, SAR values of 0.58 and 1.04 W/Kg were measured. Vector network analyser and anechoic chamber were used to test the performance of antenna and AMC surface prototypes. There is a substantial agreement among measured and simulated parameters of an antenna. Consequently, the developed antenna combination with the AMC structure is suited for wireless devices in ISM and WLAN bands, often used in IoT-based healthcare systems.

Solar Cell Integrated Wearable Patch Antenna on Artificial Magnetic Conductor for On-Body and In-Body Communications

This paper presents a patch antenna on a jeans textile with an artificial magnetic conductor (AMC) structure stacked on a solar cell for wearable applications in the Industrial, Scientific, and Medical (ISM) band. Meanwhile, the loading of the AMC reflector increases the radiation efficiency and antenna gain and also results in a reduction in specific absorption rate levels. As examination cases, two textile antenna designs loaded on 7 × 8 patches of AMC plane with the ground plane of both fully copper conductor and partially copper aided with solar cells were fabricated and tested, presenting a strong agreement between simulation and measurement. Its measured impedance bandwidth is 13.79% (2.16 GHz–2.48 GHz) with good return loss and voltage standing wave ratio features in the operating band where it is being used. Besides being a source of electricity, the silicon solar cells are also used as a radio frequency ground plane for the AMC plane. They can produce363.08 mW.

Development of a metamaterial‐based compact applicator for hyperthermia

AbstractA compact focused metamaterial‐based applicator is investigated for hyperthermia cancer treatment in this letter. The metamaterial‐based applicator consists of a double spiral antenna (DSA), an artificial magnetic conductor (AMC) as a reflector, and a frequency selective surface (FSS) as a lens. An AMC structure (64 × 64 mm2) is placed in the back of the antenna at a 5 mm distance that converges the bidirectional field pattern of the antenna into the directional field pattern. Further, to increase penetration inside the tissue, an FSS structure (64 × 64 mm2) is placed at the top of DSA at a distance of 4 mm. The FSS directs the energy toward the tumor location and provides a uniform heating pattern. The field and temperature distribution are numerically obtained for the proposed applicator in the heterogeneous phantom (layers of skin, fat, and muscles), and the performance of the applicator is evaluated in terms of the specific absorption rate, penetration depth, and effective field size. The performance of the applicator is also analyzed for a deeply placed (at 16 mm from the skin surface) irregular‐shaped tumor. The temperature profile calculates 44°C at an input power of 2.5 W. The results show that the applicator is capable of heating sufficiently deep‐seated tumors.

Out-of-Band RCS Reduction of HF/VHF Whip Antenna Using Curved AMC Structures

The whip antennas used for HF/VHF band communication on the vehicles or ships are generally larger in length and diameter. It would be of great significance if it could be easily hidden from microwave detection radar searches. Aiming at the lower RCS of whip antenna in X-band and maintaining the original impedance and radiation characteristics under high-power input, we propose a whip antenna integrating a novel curved artificial magnetic conductor (AMC) to achieve the RCS reduction in X-band. The backscattering of the cylinder can be dispersed by using the 180° phase difference cancellation principle of different AMC structures, and the mechanism is demonstrated by simulation and experiment. The measurements are in good agreement with the simulations, and the measurement results indicate that in the band of 8–12 GHz, the backward RCS is reduced by an average of 11.2 dBsm in VV polarization and by 10.2 dBsm in HH polarization. Moreover, the proposed whip antenna can be applied to high-power HF/VHF transmitting systems, and the withstand voltage can reach 15 kV (continuous output above 10 kW). This method has important theoretical significance and practical values for the whip antenna in practical engineering applications.

Design and development of a double spiral antenna with an artificial magnetic conductor structure for hyperthermia treatment

A double spiral antenna with an artificial magnetic conductor (AMC) is designed, fabricated, and experimentally tested for hyperthermia treatment as a microwave power radiator. The proposed double spiral antenna has a compact structure, designed on an FR4 substrate with a thickness of 1.6 mm, and the dimensions of the proposed antenna is 32 × 32 × 3.27 mm3. The width and space between the spiral arms is 1.54 and inner and outer radius of the spiral is arm 1 and 12.82 mm. The antenna is fed by aperture feeding having dimensions of 16 × 14 mm2 that enhances the antenna's bandwidth. Further, an AMC unit cell (as a reflector) is designed to enhance the proposed antenna's performance, which is designed on an FR4 substrate with a size of 16 × 16 × 1.6 mm3. The size of an AMC structure is optimized to 64 × 64 mm2, consisting of 4 × 4 unit cells and placed at a 5 mm distance at the backside of a double spiral antenna, which enhances the directivity, and gain of the proposed antenna and also converges backfield in the forward direction. At a 5 mm distance, the AMC structure behaves as a reflector and converges all back field radiation in the required direction to make a directional radiation pattern which enhances the antenna's bandwidth and gain. The proposed applicator (antenna + AMC structure) is simulated with a heterogeneous phantom (112 × 112 × 86 mm3), and the performance of the applicator is evaluated by using a specific absorption rate (SAR) in terms of penetration depth (PD) and effective field size (EFS) inside the phantom. The PD and EFS are improved when an AMC structure is placed at the backside of the antenna. Further, the proposed applicator is analyzed for the regular shape of the tumor inserted in the phantom, with the tumor size as 20 × 20 × 10 mm3, located at 10 mm distance from the skin surface. The study of temperature distribution inside the phantom is also done when 2.5 W of power is applied to the applicator in a simulation environment, a temperature rise of the tumor that between the range of 41–45°C is observed, allowing the proposed antenna with an AMC structure to be a good choice for the hyperthermia treatment.

A Low-Profile Wearable Textile Antenna Using AMC for WBAN Applications at 5.8GHz

This paper presents a low-profile, wearable textile antenna, designed for Wireless Body Area Network (WBAN) applications operating in the 5.8GHz band for Industrial, Scientific, and Medical (ISM) applications. An Artificial Magnetic Conductor (AMC) structure was used to improve antenna performance and protect the human body from back-radiation. The antenna with the integrated AMC achieved a measured gain of 8.92dBi, an efficiency of 80%, a wide impedance bandwidth of 1.4GHz (24.1%), and SAR values of 0.00103 and 0.00034W/Kg for 10g and 1g tissues respectively. The proposed antenna was studied in a worn-on-body scenario using a multilayer numerical model of the human body. The influence of the thickness of each tissue layer of the human body was investigated. The results showed that the antenna maintained its performance, a stable gain was obtained, and the SAR values were also below the IEEE guidelines that guarantee the safety of the wearer.

Low Sidelobe Series-Fed Patch Planar Array with AMC Structure to Suppress Parasitic Radiation

For automobile radar systems, the antenna array requires a low sidelobe level (SLL) to reduce interference. A low-SLL and low-cost planar antenna array are proposed in this article for millimeter-wave automotive radar applications. The proposed array consists of six linear series-fed patch arrays, a series distribution network using a grounded co-planar waveguide (GCPW), and a bed of nails. First, a hybrid HFSS-MATLAB optimization platform is set up to easily obtain good impedance matching and low SLL of the linear series-fed patch array. Then, a six-way GCPW power divider is designed to combine the optimized linear sub-array to achieve a planar array. However, since CCPW is a semi-open structure, like a microstrip line, the parasitic radiation generated by the GCPW feeding network will lead to the deterioration of the SLL. To solve this problem, a bed of nails—as an artificial magnetic conductor (AMC)—is designed and placed above the feeding networking to create an electromagnetic stopband in the working band. Its working mechanism has been explained in detail. The feeding network cannot effectively radiate electromagnetic waves into free space. Thus, the parasitic radiation can be suppressed. A low-SLL planar array prototype working at 79 GHz is designed, manufactured, and measured. The measured results confirm that the proposed low-SLL planar array has a −10 dB impedance bandwidth of 3 GHz from 77 to 80 GHz and a maximum peak gain of 21 dBi. The measured SLL is −24 dB and −23 dB in the E-plane and H-plane at 79 GHz, respectively. The proposed low SLL array can be used for adaptive cruise control (ACC) system applications.

Microstrip Patch Antenna Design with Artificial Magnetic Conductor (AMC) at 26 GHz

Advancements in 5G wireless communication systems are expected to enhance the communication capability significantly to achieve the higher data rate by accommodating broad bandwidth. In this paper, three compact sizes of rectangular microstrip patch antennas that were made of RT5880, FR-4 and RO3003 substrates with 0.5 mm thickness and resonating at 26 GHz were proposed for the 5G applications. However, the antenna having narrow bandwidth and low gain which contributes to drawback of this microstrip patch antenna design and hence an Artificial Magnetic Conductor (AMC) was proposed to overcome this drawback. The 3.5 mm  3.5 mm rectangular loop-slot AMC was designed at 26 GHz using FR-4 and it is found that integrating the AMC structure to the printed patch antenna significantly improved the gain and directivity of the antenna. With the help of AMC design, for RT5880 patch antenna, the gain increased for approximately 5% from 6.04 dBi to 6.34 dBi. Besides that, RO3003 patch antenna gain improved for 78.62% from 4.77 dBi to 8.52 dBi and for FR-4 patch antenna, the gain escalated from 2.24 dBi to 7.86 dBi (roughly 251% increment). As a conclusion, the directivity of RT5880 substrate solely decreased for approximately 13.75%. Meanwhile for RO3003 and FR-4 patch antennas, with the assist from AMC design, the directivity of antenna escalated for more than 120 % compared to without AMC and this proved that this design has potential to be used for 5G wireless networks and applications.

An On-Film AMC Antenna Insert-Molded in Earbuds with Enhancement in In-Ear and In Situ Received-Signal Sensing.

In this paper, a novel thin and flexible antenna is proposed for earbuds to gain an improvement in their wireless signal-sensing capability as a film-based artificial magnetic conductor (AMC) structure. As antenna designs for earbuds face challenges of being embedded beneath the top cover of the earbud, conformal to curved surfaces, and very close to metallic ground and touch-panel parts, as well as scarce degrees of freedom from feeding conditions and functional degradation by human tissue, unlike conventional techniques such as quasi quarter-wavelength radiators on LDS and epoxy molding compounds (relatively thick and pricy), an antenna of a metal pattern on a film is made with another film layer as the AMC to mitigate problems of the antenna in a small and curved space of an insert-molded wireless device. The antenna was designed, fabricated, and embedded in earbud mockups to work for the 2.4 GHz Bluetooth RF link, and its functions were verified by RF and antenna measurement, showing that it could overcome the limitations in impedance matching with only lumped elements and poor radiation by the ordinary schemes. The input reflection coefficient and antenna efficiency were 10 dB and 9% better than other methods. In particular, the on-film AMC antenna (OFAA) presents robustness against deterioration by the human tissue, when it is placed in the ear phantom at the workbench and implemented in an in situ test using a large zorb ball mimicking a realistic sensing environment. This yielded an RSSI enhancement of 20–30 dB.

Platform-Tolerant Nested-Slot RFID Tag Antenna Based on Jigsaw-Shaped Metasurface

A novel low-profile (<0.005 λ) jigsaw-shaped metasurface for platform-tolerant nested-slot radio frequency identification (RFID) tag antenna is proposed in this letter. It consists of a 4 × 4 array of rippled-edged patch units with a central through-via. Compared with the widely used patch-unit artificial magnetic conductor structure, the proposed jigsaw-shaped metasurface is proved to suppress the surface waves effectively and reflect the electromagnetic waves in phase in the industrial scientific medical band of 902–928 MHz, therefore, it could improve the frequency and radiation stability of the nested slot RFID tag antenna on different platforms, and enhance the radiation performance of the tag antenna. The prototype of the metasurface was fabricated and measured as an interlayer of the nested-slot RFID tag and different platforms. The measured operation frequency band remains stable, and the measured reading range has a range deviation of less than 8.7% on different platforms.

Design of a wideband patch antenna and performance enhancement using an AMC reflector surface for on-body communication at 2.45 GHz

ABSTRACT Wireless biotelemetry enables the formation of communication link from living body to an external monitoring device. Isolation of near field electromagnetic (EM) waves from body tissue, and wide bandwidth to avoid frequency detuning in different biological environments are the important parameters of on-body antennas. In this paper, a conformal defected ground patch antenna with artificial magnetic conductor (AMC) is introduced for on-body communication. Initially, a quarter wave wide band antenna with a shorting pin is designed to operate at 2.45 GHz. It resonates effectively on body tissue but most of the near field EM radiations are absorbed by tissue. Poor radiation efficiency of 10% and high specific absorption rate (SAR) value of 7.73 W/Kg were obtained. Thus, to reduce the effect of tissue loading on antenna performance an AMC-based structure is added. Better impedance matching, high efficiency (65%) and directivity (7.3 dBi) is achieved with AMC structure. Furthermore, unidirectional radiation pattern with SAR value of 1.43W/Kg is attained. Wide bandwidth of 600 MHz on phantom enables the antenna to withstand frequency detuning effect due to body postures and movements. Antenna robustness is analysed by bending the structure at different radii along X-axis and Y-axis.