Artificial Magnetic Conductor Structure Research Articles

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.

A Dual-Band Wearable Conformal Antenna Based on Artificial Magnetic Conductor

In order to improve the effectiveness of the antenna performance of wearable devices, a dual-band flexible monopole antenna with a 3 × 3 artificial magnetic conductor structure of the ISM band is proposed by using meander technology. An annular-shaped artificial magnetic conductor (AMC) is placed directly below the antenna, which can be better suitable for wireless body area network (WBAN) applications. A polyimide substance is used as the antenna substrate, which makes the antenna bendable and thin. Benefiting from the in-phase reflective properties of the double ring AMC structure, the antenna has good radiation characteristics. Compared with the single antenna, numerical simulation and measurement results show that the gain of the AMC-loaded antenna is increased by 4.54 dBi and 3.86 dBi at 2.45 GHz and 5.8 GHz, respectively. In addition, the specific absorption rate (SAR) of 1 g is only 0.35 W/kg at 2.45 GHz and 0.39 W/Kg at 5.8 GHz when the antenna is placed on human tissue, which is far below the Federal Communications Commission (FCC) standard. The antenna is easy to be conform to the human body and has strong robustness to structural deformation and human body load.

A novel miniaturized, multiband, AMC-integrated CPW-fed antenna operating at millimetric wave frequencies suitable for IoT applications

PurposePlanar periodic metallic arrays behave as artificial magnetic conductor (AMC) surfaces when placed on a grounded dielectric substrate, and they introduce a zero-degree reflection phase shift to incident waves. The antenna designers have new challenges while designing the AMC structure. The steps followed in designing the structure are as follows: 1) Designing the antenna, aimed to operate at millimetric wave frequencies, (2) Designing the AMC at desired frequencies, (3) Integrating the antenna design and AMC to resonate at millimetric wave frequencies and (4) Validate the output parameters of the antenna to be suitable for Internet of Things (IoT) applications.Design/methodology/approachThe antenna is integrated with artificial material known as high impedance surface (HIS) for performance enhancement. A miniaturized, multiband, enhanced gain, AMC-integrated CPW-fed antenna is proposed and aimed to operate at millimetric wave frequencies, which is most suitable for IoT applications. The developed antenna operates at an extremely high range (30–300 GHz), i.e. from 40 to 60 GHz with the return loss values at lesser than −20 dB, and gain is greater than 10. The antenna is developed and simulated by using HFSS software.FindingsAn extensive research study has been carried out to develop a low profile, high gain and optimized antenna. The first two steps are separately designing the antenna and the AMC unit cell at the desired frequencies. The third step is finding the antenna or AMC radiating parts responsible for each resonant frequency by analysing the surface current distribution. CPW fed along with AMC integration has made the antenna feasible to achieve the extremely high frequency (EHF) range, i.e. 40–60 GHz, which is highly adoptable in IoT applications.Originality/valueThe result represented that the developed antenna is resonating at EHF rank with high gain and good imped matching when it is being compared with the previous models and has only CPW fed without having AMC structure integration. It is evident that the antenna which has only CPW fed has resonated at lower frequency than EHF range and justified output characteristics. But when it is embedded with the AMC structure, it resonates at the EHF range, which makes the antenna highly suitable for IoT applications, with more accuracy and high data rate possibility.

Tri‐band phase switched screen based on time modulation

A tri-band phase switched screen is proposed based on a dual-band artificial magnetic conductor (AMC) for radar cloaking. The electromagnetic band gaps of the AMC structure can shift from a dual-band working state, that is, 2.44 and 3.65 GHz, to another dual-band of 3.56 and 6.01 GHz, by adjusting the biasing current on the four PIN diodes. Based on the AMC structure above, a potential tri-band PSS is realized through different switching schemes, and therefore achieves good stealth effects during the three bands above.

An AMC-Based Liquid Sensor Optimized by Particle-Ant Colony Optimization Algorithms

This paper proposes a liquid sensor based on artificial magnetic conductor. The artificial magnetic conductor structure is optimized numerically using particle-ant colony optimization algorithm to increase the freedom of structural optimization exploration while reducing the time consumption. In the optimization process, the resonant frequency is kept at 2.45 GHz to ensure that the operating frequency is within the industrial scientific medical (ISM) band. The optimized artificial magnetic conductor is combined with a broadband antenna to build a liquid sensor. The designed sensor is fabricated and tested by loading butan-1-ol, propan-2-ol, ethanol, methanol, and water. The liquid samples can be injected directly into the channel without the need for additional expensive microfluidic chip such as polydimethylsiloxane, thereby greatly reducing the fabrication cost. A maximum sensitivity of 3.48% and a wide application range up to 78 are achieved, verifying the potential of the proposed sensor for low cost and real time monitoring of liquid samples in practical applications.

Low profile and miniaturized dual‐band antenna based on graphene assembled film for wearable applications

Wearable electronic devices are the basic components of wireless human body local area network. Due to their close contact with the human body, it is necessary to improve the flexibility and isolation of the antenna to maintain high signal transmission performance. In this paper, a flexible wearable antenna based on highly conductive graphene assembled film (GAF) and polydimethylsiloxane dielectric material is proposed. The planar combination of the powerful novel materials and supple polymer maximizes the flexibility and chemical stability of the antenna. In addition, the coplanar waveguide feeding and artificial magnetic conductor (AMC) structure enhance the efficiency and isolation with an easier preparation process. In the wearing measurement, the GAF antenna operates at 3.5 GHz for 5G communication frequency band and 5.8 GHz for ISM (Industrial, Scientific, Medical) frequency band. The GAF antenna has a minimizes SAR level, which in accordance with IEEE C95.1 International standard, by taking up a small space with 50.5 × 48.5 × 2.08 mm3. Furthermore, the GAF antenna has good radiation performance both under several different bending conditions and human body conditions.

Multilayered metamaterials array antenna based on artificial magnetic conductor's structure for the application diagnostic breast cancer detection with microwave imaging

In this work, a small multilayer ultra-wideband (UWB) patch antenna for microwave breast imaging (MWI) applications was developed both theoretically and experimentally. However, to improve the antenna performance relating to the bandwidth (BW), the radiating element of the suggested initial antenna is modified by adding a modified split ring resonator (SRR) and slits in the patch as well as the ground plane. Then, to achieve the requisite antenna properties for MWI applications such as the gain and directivity, the antenna is equipped with a uniplanar artificial magnetic conductor (AMC) structure made up of a 3 × 3 array of square modified SRR unit cells. The final proposed prototype has a relatively small size of 20 × 19 × 1.6 mm3 and it accomplishes a return loss below -10 dB (S11< -10 dB) at overall BW of 7 GHz (4.1 – 9.7 GHz) with more than 5 dBi realized gain. In this way, the characteristics of the fabricated antenna are measured to examine the antenna performance. Indeed, the fidelity factor of face-to-face (FtF) and side-by-side (SbS) scenarios are also noticed for the same frequency range. In the final analysis, a simulation model of the antennas, which operate as a transceiver, and a breast phantom model with tumor sample are proposed for detecting cancerous tumor cells within the breast.Hence, the proposed design is suitable in the biomedical applications such as tumor cell detection.

Controlling Graphene Sheet Resistance for Broadband Printable and Flexible Artificial Magnetic Conductor-Based Microwave Radar Absorber Applications

Current artificial magnetic conductor (AMC) designs use metallic patterns on rigid substrates and focus on shapes and sizes of AMC structures, rather than on material performance, which has hindered operation bandwidth and design flexibility. Here, we introduce printed graphene AMC-based broadband and flexible microwave radar absorbers, which not only redirect but also absorb the incident wave so to broaden the operation bandwidth. Contrasting to other reported works, the phase characteristics of the AMCs are realized through the control of the surface resistance provided by printed graphene laminates. We produced a variety of AMC structures, composed of printed graphene circular ring arrays with exactly the same shape and size, but different sheet resistances. By carefully designing the sheet resistance of printed graphene laminates, the optimized anti-phase reflection cancellation between AMCs can be achieved. With printed graphene AMCs and flexible dielectric substrate, the absorber presented in this work has a broadband effective absorption (above 90% absorptivity) from 7.58 GHz to 18, is polarization insensitive under normal incident, and can work at relatively wide incident angles. Furthermore, this absorber is capable of bending easily with notable performance, which makes it ideal for applications with irregular and uneven shapes.

Analysis of the Electromagnetic Absorption in a New Design of PIFA Antenna Using Metamaterials

This paper presents the design, simulation and fabrication of a miniaturized wearable dual-band antenna put on a rigid substrate and operable at 2.45/5.8 GHz for wireless local area network applications. The electrical and radiation characteristics of the developed antenna were obtained by means of the technical insertion of a slot to tune the operating frequencies. To study the impact of the electromagnetic radiation of the structure of the human body, it is necessary to minimize the back radiation towards the user. Therefore, in this work, a multi-band artificial magnetic conductor (AMC) was placed directly above a dual-band planar inverted F antenna to achieve a miniaturization with excellent radiation performance. The simulations were carried out using the computer simulation technology CST Microwave Studio (CST MWS). A good agreement was achieved between the simulation and experimental results. The comparison of the measurement findings indicates that, when the antenna was backed by the AMC plane, the gain improved from 1.84 to 3.8 dB, in the lower band, and from 2.4 to 4.1 dB in the upper band. The front-to-back ratio of the AMC backed PIFA antenna was also enhanced. Then, to ensure that the proposed AMC structure is harmless to the human body, this prototype was placed on three-layer human tissue cubic model. It was observed that, due to the inclusion of an AMC plane, the peak specific absorption rate (SAR) decreased to 1.45 and 1.1 W/kg at 2.45 and 5.8 GHz, respectively (a reduction of around 3.7 W/kg, compared with an antenna without (AMC).

Tunable wideband THz graphene-based artificial magnetic conductors

Graphene-based artificial magnetic conductor (AMC) structures featuring wideband and tunable responses at terahertz frequencies are presented. The unit cells of the proposed structures comprise curved coupled microstrip line (CCML) resonators, in which small graphene patches are added for electrical tuning. An advantage of the present structure is that the full range of graphene chemical potential, from 0 to about 1 eV, can be used to tune the center frequency; therefore the AMC is tunable in a larger frequency range, for which the return loss remains near 0 dB. This feature is missing in the previous tunable graphene-based AMC structures. A typical design in the present work yields a fractional bandwidth of 45% and an electrically tunable center frequency in a range from 3.7 to 4.4 THz.

Human Body Specific Absorption Rate Reduction Employing a Compact Magneto-Dielectric AMC Structure for 5G Massive-MIMO Applications

A compact artificial magnetic conductor (AMC) structure for the application of specific absorption rate (SAR) reduction is presented in this paper. A magneto-dielectric (MD) structure as a host of AMC substrate is used to miniaturize the AMC size. The magneto-dielectric has been designed with a low-profile spiral loop in a way to have a high permittivity and permeability for the desired center frequency of 3.5 GHz. Simulation results confirm the zero-degree reflection phase of the proposed AMC unit cell. Moreover, a 70% reduction has been achieved in comparison to the conventional AMC. To validate the simulation results, a prototype of the board is fabricated and measured with a coplanar waveguide (CPW) antenna for the reflection coefficient. The measurement results display an excellent agreement with the simulation ones. A VOXEL model of a human body is utilized to determine the SAR value of the proposed structure. Considering the maximum SAR value for an average of 10 g human tissue, more than 70% SAR reduction is verified for the CPW antenna with the recommended MD-AMC structure compared to a conventional single CPW antenna.

FULLY TRANSPARENT METAMATERIAL AMC BACKED CPW FED MONOPOLE ANTENNA FOR IOT APPLICATIONS

In this paper, a fully transparent antenna comprising of an Artificial Magnetic Conductor (AMC) backed Co-planar Waveguide (CPW) fed dual-ring monopole is presented. The monopole antenna and AMC structure achieve transparency due to the use of AgHT-8 conductive oxide and Plexiglas substrate. Measured antenna performance shows an impedance bandwidth of 5.3 – 6 GHz (12.4%) in the U-NII-1 to U-NII-4 frequency band with a peak gain of 5.7 dBi which is approximately an increase of 4.5% and 3.9 dBi, respectively, as compared to the standalone antenna. The simulation and the measurement results agree well with each other which proves the validity of the proposed design. To the best of our knowledge, the proposed antenna is the first fully transparent antenna design combining a transparent radiator and a transparent AMC structure.

High gain, wideband and low mutual coupling AMC-based millimeter wave MIMO antenna for 5G NR networks

A high gain and wideband multiple-input multiple-output (MIMO) for 5G new radio (NR) networks is introduced in this paper. The single unit is a monopole antenna with partial ground plane and two small triangles are cut out from the patch to produce the proposed frequency band. The two elements are located orthogonal to each other in order to reduce the mutual coupling without using isolation structure at the desired frequency 28 GHz. An artificial magnetic conductor (AMC) is located underneath the MIMO antenna to improve the gain by about 55% over the entire achieved frequency band (26-31.5 GHz). The Suggested antenna model with the AMC structure is fabricated to verify the simulation results in terms of S-parameters, radiation patterns, gain, and diversity parameters. It is worth noting that the experimental results have the same trend of the simulation ones which makes the suggested AMC-based MIMO antenna applicable for 5G NR networks.

C-shaped antenna based artificial magnetic conductor structure for wearable IoT healthcare devices

A wearable C-shaped antenna based on a fabric material operating at 2.4 GHz frequency is proposed for use in flexible/wearable IoT medical systems. The wearable IoT device plays a key role in medical applications, and the antenna is a key part of it. Loading the presented antenna on the body models showed a frequency detuned with the gain and efficiency reduced from 1. 28 to −9 dB and 90% to 10%. In addition, the SAR did not meet the safety health requirement defined by the FCC or ICNIRP standards. Therefore, an “Artificial Magnetic Conductor” structure (AMC) is added to the C-shaped antenna to overcome these problems. The AMC acts as shielding material between the human skin and the presented antenna because of its 0° reflection phase, which mimics the action of the Perfect Magnetic Conductor (PMC). The overall size of the proposed design was 54 × 54 × 3.9 mm3. Numerical and experimental findings indicated that integrating the AMC structures with a C-shaped antenna was robust for body deformation and load. The C-shaped antenna worked equally well with the AMC, whether positioned in free space or on the chest or the arm of the human body. The integrated antenna with AMC structures has excellent performances. The gain and efficiency without loading on the chest were 6.49 dB and 84%, respectively. While for loaded on the chest were 6.21 dB and 81%, respectively. It also decreased the back radiation and raised the Front to Back Ration (FBR) by 13.8 dB. SAR levels have been reduced by more than 90% between the FCC and ICNIRP standards compared to the C-shaped antenna alone, which does not comply with the standards. As a result, the C-shaped integration with AMC structures is highly suitable for assembly in any wearable system.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11276-021-02770-4.

An Artificial Magnetic Conductor-Based Wideband Circularly Polarized Antenna with Low-Profile and Enhanced Gain

A broadband circularly polarized (CP) antenna with enhanced gain and low profile is proposed. Two identical dipoles with full wavelength are placed orthogonally to generate radiation waves with equal amplitude and orthogonal polarization. The arms of the dipoles are designed as stepped patches to enlarge the impedance matching bandwidth and axial ratio (AR) bandwidth. Crossed-dipoles with full wavelength are utilized as the main radiators to provide a wide operating bandwidth and enhanced gain, and an artificial magnetic conductor (AMC) structure is introduced as the reflector to reduce the profile of the whole antenna. Due to the introduction of the AMC structure, the antenna profile is reduced from 12.8 to 6.9 mm, that is, reduced to 0.14λ0 (where λ0 denotes the wavelength corresponding to the center frequency of the passband, 4.0–8.5 GHz). A simulation and experiment were carried out to verify the performance of the proposed antenna. Experimental results showed that the antenna realized an impedance bandwidth of 74%, an AR bandwidth of 67.7%, a peak gain of 12.1 dBic, and an average gain of 10.69 dBic.

A Wearable Button Antenna Sensor for Dual-Mode Wireless Information and Power Transfer.

A novel wearable button antenna sensor is proposed for the concept of simultaneous wireless information and power transfer (SWIPT). This integrates two working modes for the transfer of power and information, respectively, and optimizes transfer efficiency. An omni-directional radiation pattern is achieved in the 3.5 GHz World Interoperability for Microwave Access (WiMAX) band to support on-body wireless communications, while a circularly polarized broadside radiation pattern is obtained in the 5 GHz wireless local area networks (WLAN) band to harvest power. The measured −10 dB return loss bandwidths are 4.0% (3.47–3.61 GHz) in the lower band, and 25.0% (4.51–5.80 GHz) in the higher band, respectively. An artificial magnetic conductor (AMC) structure with wideband characteristics is applied to obtain a low-profile design and to increase the stability of the antenna sensor. A high radiation efficiency of over 80% in the whole working band is observed. The specific absorption rate (SAR) of the proposed antenna sensor is below 0.509 W/kg at 3.55 GHz, and below 0.0532 W/kg at 5.5 GHz, respectively, which is much lower than the European standard threshold of 2 W/kg. All these characteristics make the designed antenna sensor suitable for on-body information transmission and off-body energy harvesting. The antenna sensor has been prototyped. Simulations and measurements agree well, proving the validity of the new concept.

Ultra- Thin Artificial Magnetic Conductor with Metallic Posts for a 94 GHz On-chip Antenna

System-on-Chip has become an excellent solution for the high-level integration of systems. However, the primary barrier is the insufficient radiation from the on-chip antenna due to the lossy silicon substrate. In this paper, an ultra-thin artificial magnetic conductor (AMC) surface is proposed whose ground plane is on the top of the substrate to isolate it completely, and the thickness is reduced to house AMC within the oxide layer of the standard CMOS process by employing metal vias in the stack-up. The AMC structure is implanted for a 94 GHz on-chip monopole antenna and shows gain enhancement by 4.5 dBi with a radiation efficiency of 23%.

Design of High Gain Wearable Antenna Based on Wireless Body Area Network Communications

This paper presents a wearable antenna for Wireless Body Area Network communication. A 3×3 array artificial magnetic conductor structure (AMC) is loaded at the bottom of the antenna to reduce the backward radiation and improve the antenna gain. The simulated results show that the antenna can completely meet the working requirements in the bent state. After the addition of AMC array, the maximum gain reaches 7.53 dB, and the SAR value of human tissue can be reduced by about 94%. In addition, we have also processed and tested the antenna. The measured results are in good agreement with the simulated results, and its working bandwidth includes the low-frequency band of the ISM frequency band for WBAN communication, which can meet the working requirements of the antenna.