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In this paper, an ultra-wideband, angle and polarization-insensitive laser assisted graphene metamaterial absorber is presented. The design consists of double graphene resistive layers with the combination of three dielectric substrates. The graphene imbedded nano-magnetic material Fe3O4 has been synthesisedby laser direct writing technology, which demonstrates a high degree of uniformity with deviations less than 6% for different designed values of sheet resistance. Numerical simulation and analytical studies were carried out in order to analyze the absorption mechanism. The measured results confirm that the absorber operates from 1.32 to 17.9 GHz with over 90% absorptivity. The absorber achieves 173% fractional absorption bandwidth with a thickness of 0.068λL.

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 GHz, 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.

Electromagnetic (EM) radiation pollution is increasing attention due to the popularization of electronic equipment. In recent years, various nanomaterials have been widely designed and developed for the enhancement of their EM interference shielding effectiveness (EMI SE). However, large amounts of reported reviews focus on carbon materials and transition metal carbides (e.g., MXenes), while the applications of metal nanocomposites in EM interference shielding are still suffering from the insufficient systematic analysis. Therefore, this paper provides comprehensive information on material selection, whole structural design, engineering preparation schemes and the latest cutting-edge techniques to elaborate the metal nanocomposites (thickness ≤1 mm) for EMI SE. We firstly describe the principle of EMI SE and structure design. Then we also investigate the material selection based on metals such as silver, copper, nickel, and their combinations with carbon materials or other materials. Finally, we compare the strengths and weaknesses of various preparation schemes and identify the state-of-the-art cutting-edge methodologies.

This paper presents the detailed design, analysis and measurements of new configuration of quad-band antenna. The antenna is designed using a new uni-planar complementary split ring resonator (UP-CSRR) unit cell. The UP-CSRR unit cell is etched in the top plane of a microstrip patch which reduces the back radiation and enhances the antenna efficiency. The structure has advantage of the presence of complete ground plane that supports a typical broadside radiation. The designed antenna is resonating at 1.9, 3.3, 3.9 and 4.2 GHz with reflection coefficient lower than –10 dB. Moreover, the antenna has a patch size of 3.5 cm × 4 cm which is a consequence of the new IP-CSRR configuration smaller size compared to conventional CSRR.

To date semiconductor switches are still the main enablers for electrical circuit and system reconfigurability. They however not only consume dynamic power but also dissipate static power, the former for performing on/off operation and latter for holding on/off state. These semiconductor devices are volatile and not energy efficient due to the need for holding voltage and can significantly increase the system power consumption where hundreds and thousands of switches are needed, such as in large reconfigurable intelligent surfaces and large antenna arrays. In this work, we report a non-volatile reconfigurable antenna that can switch between dual-band at 2.4 GHz and 5 GHz to a single band at 3 GHz. The measured results including reflection, gain and radiation patterns reveal promising performance, experimentally demonstrating a new approach of design and realization of RF switch integrated multi-band reconfigurable antennas. This zero-static power mechanism, along with easy fabrication on the flexible substrates would be very beneficial for Internet of Things (IoT) applications.

This paper proposes an accurate model for yarn-based embroidered coil antenna used in Near Field Communication (NFC) applications. Traditionally, the inductance of a coil-shaped antenna is calculated using the Wheeler’s equation, while accurate enough for metallic coil geometries, the results from Wheeler’s equation have more than 20% errors when being applied to yarn-based embroidered antennas. We have discovered that this discrepancy is related to the parasitic capacitance, which is caused by the subtle gaps along twisted fibers. Experiments demonstrate that the parasitic capacitance has significant impact on the overall performances of the coil antenna. In this paper, an equivalent model for yarn-based coils is proposed to take into account of the parasitic capacitance and antenna geometrical characteristics. Compared with traditional Wheeler’s equation, the inductance calculated from this proposed model is within 5% from the measured value. Additionally, the electromagnetic performance of the embroidered coil is resilient to mechanical deformation. When being used as a coupling antenna, it can harvest energy and power-up the NFC-based platform for body-area-network applications.

A broadband microwave metamaterial absorber with wide-angle property is introduced in this paper. The bandwidth of effective absorption (over 90% absorptivity) of the proposed absorber is from 2.2 GHz to 18.4 GHz, covering almost the whole S-, C-, X-, and Ku-band, with relative absorption bandwidth of 157%. The total thickness of the proposed absorber is 15 mm, which corresponds to 0.11λ at the lowest operating frequency. To provide wide-angle and broadband frequency matching, a wide-angle impedance matching layer is used in the unit cell design. The proposed absorber can realize more than 80% absorptivity for TE polarization and more than 90% absorptivity for TM polarization from S-band to Ku-band when the incident angle is less than 50°. Equivalent circuit method is used to analyze the proposed absorber and the circuit model analysis results agree quite well with the numerical full-wave simulation.

This paper presents the experimental verification of the tunable characteristics of a ferrite composite right/left handed coupled line coupler. The coupler is designed using two coupled CRLH-CRLH transmission lines. The coupler is designed to demonstrate equal through and backward coupling. The novel coupler has been designed and realized in coplanar waveguide configuration on a ferrite substrate. The tunable characteristics are achieved by changing the applied DC magnetic bias to the ferrite substrate. The measurement results reveal that the coupler’s fractional bandwidth can be tuned from 29% to 69% by varying the applied DC magnetic bias from 1000 Oe to 1750 Oe. Within the tunable bandwidth, the maximum backward coupling is −5 dB. The coupler has high forward coupling isolation, close to −30 dB at its centre operating frequency. In addition to its tuning capability, the coupler has the advantages of its compact size; it has the length of 11.5 mm and not-so-tight line separations of 2.5 mm. Furthermore the coupler only requires low DC magnetic bias.

Wearable e-textile near-field communication (NFC) radio-frequency identification (RFID) antennas fully integrated with garments using embroidery techniques, which enables everyday clothing to become connective to wireless communication systems, is presented. The e-textile wearable antennas have been designed through full electromagnetic wave simulation based on the electrical properties of conductive threads and textile substrates at the high frequency band, allocated for NFC wireless communications. The e-textile wearable NFC antenna performance under mechanical bending as well as human body effects have been experimentally studied and evaluated; the antennas can operate under significantly bending angle and body effects attributed to its broad operating bandwidth. This is highly desirable and distinguished to conventional NFC antennas; the proposed e-textile wearable NFC antennas can be placed almost any place on clothes and still capable to communicate at the desired operating frequency of 13.56 MHz. The maximum read range of the e-textile wearable NFC tags is measured to be around 5.6 cm, being compatible to typical commercially available metallic NFC tags. The e-textile wearable NFC tags can lead to numerous potential applications such as information exchange, personal security, health monitoring and Internet of Things.

lass‐J GaN HEMT power amplifier (PA). A graphene resonant‐tunneling diode (RTD) NFC is proposed to provide negative differential resistance characteristics and to create an effective negative capacitance. The NFC is integrated in the input matching network of the Class‐J GaN HEMT PA to cancel out the transistor input parasitic capacitance so as to enhance PA bandwidth, efficiency, output power, and gain. The PA design is based on Cree's packaged GaN HEMT CGHV40030F biased with drain supply voltage of 50 V at quiescent drain‐to‐source current of 44 mA. The PA operates from 3.4 to 4.0 GHz with center frequency of 3.7 GHz. The effective negative capacitance of the NFC from 3.4 to 4.0 GHz stands at −3.3 to −6.0 pF. An effective capacitance of −3.7 pF has been obtained at 3.7 GHz. The PA has small signal gain of 16.1 dB at 3.7 GHz. Large signal simulation input power sweep from 1 to 33 dBm at 3.7 GHz, indicates that the PA has 57.8% drain efficiency, 54.7% power added efficiency (PAE), 44.6 dBm (28.8 W) output power and 11.6 dB transducer power gain at input power of 33 dBm.

This paper introduces different varieties of novel composite right / left handed metamaterials devices with novel magnetic operation properties. The reported devices are discussed in terms of their theoretical. The reported devices have the advantages of their small size, multi frequency band in addition to broadband operation (≈60 %) compared to their conventional design. Moreover, these devices are designed to illustrate novel magnetic properties such as their tuning and non reciprocity operation capabilities. Theoretical explanations supported by simulation results of presented devices confirmed the operation of a tunable and nonreciprocal coupler and tunable transformer. The novelty and advantage of the reported devices are their combined properties of compactness and nonreciprocity. Furthermore the devices require very low external DC magnetic bias due to its much lower demagnetization compared to the microstrip configuration. Accordingly, the devices can be applied in many RF front end novel applications such as circulators and isolators.

This paper proposes high power microstrip non-Foster Class E GaN HEMT amplifier. The power amplifier (PA) was designed based on Cree CGHV40030FP GaN HEMT biased at drain supply voltage of 50 V and cut-off gate voltage of −3 V. Non-Foster circuit has been used in the input matching network to generate the negative capacitance required to cancel out the gate-source capacitance of the power transistor. The PA operates from 3.1 to 3.3 GHz at 3.2 GHz center frequency. The PA has 57.6% drain efficiency, 52.9% PAE, 42.5 dBm output power and 10.5 dB transducer power gain at 32 dBm input power.

An ultra-wideband and polarization-insensitive microwave absorber, which is composed of three layers of metasurfaces with different patterns and sheet resistances, is proposed in this paper. The bandwidth of effective absorptivity (over 90%) is from 6 GHz to 50 GHz, with relative absorption bandwidth of 157%. The equivalent circuit of the proposed absorber is investigated thoroughly. The circuit model analysis results agree quite well with the numerical simulation, which indicates the accuracy of the equivalent circuit model. The performances of this absorber under various polarizations and incident angles are also investigated. The results indicate the proposed absorber is polarization insensitive and has relatively good stability of wide incident angles.

In this paper, a printed graphene compact, low-cost, disposal, flexible and conformal, coplanar waveguide (cpw) fed, linear array antenna is proposed. It was designed for 5.8GHz radars, portable electronic devices, and commercial wireless LAN applications and manufactured by screen printing formulated highly conductive graphene ink on paper substrate. The array achieves 73% total radiation efficiency and a peak gain value of 4.5dBi at 5.8GHz, with its bandwidth ranges from 4.6GHz to 7.9GHz (52.8%). Over the operating frequency, the radiation of the antenna was proved as a typical radiation pattern of a patch antenna array.

Screen-printed graphene near field communication (NFC) tag antenna is integrated with inkjetprinted WS2 photodetector on paper substrate to fabricate battery-free wireless photosensor. Asequential multi-stack printing is employed for the wireless photosensor fabrication: the NFC tagantenna is first screen-printed with graphene conductive ink and then the photodetector is inkjetprinted with transition metal dichalcogenides (TMDs) WS2 ink as photoactive component. Highresponsivity and sensitivity are observed for the WS2 photodetector, which acts as photoactivethermistor of the NFC sensor IC chip. The highly conductive graphene nanoflakes ink enablesthe screen-printed graphene NFC tag antenna to withdraw sufficient power wirelessly from thereader to power the sensor IC chip. This work demonstrates a prospective approach to manufacture2D materials enabled electronics where the electronic circuits (normally having a large size) canbe realized by mass production screen printing and the sensing component (normally having asmall size) can be produced by inkjet printing, enabling low cost and simple fabrication methods,compatible with flexible substrates such as paper.

This paper presents the design of a coplanar waveguide fed planar monopole antenna printed by graphene nanoflakes conductive ink. By using the band rejection slits, the compact monopole can excite 2.4/5 GHz frequency bands for WIFI (2.4-2.483 GHz and/or 5.150-5.825 GHz) and WLAN applications. The measured results show the antenna has the impedance bandwidths of 730 MHz (2.11-2.84 GHz) and 2430 MHz (4.20-6.63 GHz), which can cover the WLAN 2.4/5 GHz bands. The gain and radiation pattern results also verify effective radiations from the designed dual band antenna in far field.

E‐Textiles have gained increasing momentum in wearable electronics recently. Conductive‐yarn‐based embroidered devices, with the advantages of being soft, deformable, breathable, and protective for the skin, play an important role in replacing many metallic counterparts. However, embroidered devices face many new challenges in their design methodology and fabrication processes, such as high resistivity and low Q value of the conductive yarns, as well as deformation of device geometries during wearing. Herein, a strain‐free, deformation‐resilient embroidery process for near field communication (NFC) coil antennas is introduced. Coil geometry can endure extreme deformation by stretching with up to 50% elongation, bending with curvature as small as 16 mm in radius, and can still maintain a relatively small variation in its inductance, resonant frequency, Q value, as well as its energy‐harvesting capabilities. The embroidered coil antenna is used in an NFC‐based battery‐free body sensor system. Experiments demonstrate that the system can maintain a stable performance (voltage supply, temperature sensing, and reading range) under various deformation conditions.

As the rapid development of communication industry, especially the 5G communication and IOT, there will be plenty of electromagnetic (EM) waves in the free space, which carry lots of energies. However, some of these energies are wasted in free space. To reuse these wasted energies, significantly growing interests are towards to the energy harvesting antennas. This paper is aimed to investigate a wearable antenna which can transfer RF energy from ambient sources to direct current by a soft and portable textile antenna. Among the numerous signals in mobile network, the GSM 1800, 3G, WiFi and 4G/5G will be chosen due to the city signal intensity distribution. Hence, a corresponding triple bands antenna has been designed to cover those frequency bands. The CST STUDIO SUITE is used in whole process of antenna design and simulation. The proposed antenna is a hooked dipole antenna with tuning bar (HATB) whose ends have small folded part in each side for better bandwidth performance. The presented antenna provides a wide operating band from 1.8 GHz to 2.5 GHz below -10 dB in return loss. And methods to overcome interference between antennas is found. Furthermore, using the corresponding rectifier to achieve the RF/DC conversion. The overall efficiency of whole rectifier is about 56.8 %, and output power level of the antenna system is 45.92nW. The experimental results could indicate that my textile hooked antenna harvester is a good choice for the charging system of personal wearable attachment, which could achieve low power absorbing for long distance anytime and anywhere.

In this communication, a novel compact high gain composite right/left-handed (CRLH) based leaky-wave antenna (LWA) is presented at Ku band. A half-mode substrate-integrated waveguide incorporated with a suitably oriented complementary quad spiral resonator (CQSR) is used to achieve a CRLH LWA. The unit cell is realised by a CQSR in such a way that the orientation of spirals exhibits higher leakage loss having a minimum cross coupling between them. The antenna is capable of scanning backward to forward along with a broadside direction in visible space. The proposed configuration has a length of 4.85 λ 0 which can scan within the frequency range of 13.5-17.8 GHz having a beam scanning range of 86° (-66° to 20°) and a maximum gain of 16 dBi. The simulated reflection coefficient of the proposed antenna is below -10 dB throughout the working frequency range with a side-lobe level of below -10 dB. The designed prototype is more compact in nature having high gain, fair scanning range, and good cross-polarisation level along with simpler design methodology and tuning capability to enhance the gain as well as radiation efficiency maintaining a fixed size. The proposed antenna could be a promising candidate in Ku-band applications like fixed satellite services, and broadcast satellite services etc.

This study introduces a compact asymmetric coplanar strip (ACS)-fed composite right-left-handed (CRLH) multiple-input-multiple-output (MIMO) antenna for multiband operation. The ACS fed MIMO antenna is composed of two elements; each is operating at 5, 5.8 and 6.3 GHz; for different wireless applications. The overall MIMO antenna size is compact (46 × 26 mm2). A unit cell of the CRLH connected to 50 Ω ACS fed is considered the main block of the antenna. The edge-to-edge separation between antenna elements equals 0.4λ0 at 5 GHz. The insertion loss, correlation coefficient, diversity gain and channel capacity are used to evaluate the performance of the ACS-fed MIMO antenna. The isolation higher than 25 dB and envelope correlation lower than 0.05 have been achieved without using any extra decoupling structures. The experimental results are reasonably well agreed with simulated ones.

A quad band antenna with good gain and omni-directional pattern is proposed in this paper. The antenna design is based on loading a conventional monopole antenna by three different resonators. The resonators are inspired from the shunt branch of composite right-/left-handed cell. The resonators have a simple structure and compact size. The control of the frequency bands can be achieved arbitrarily and hence the suggested design methodology can be generalized to any required bands. The fabricated antenna prototype is operating at 2.6, 3.35, 5.15, and 6.1 GHz with bandwidth wider than 100 MHz for each band. The antenna's operating principle and design procedures with the aid of electromagnetic full wave simulation are presented. Finally, the experimental results exhibit good agreement with the simulated ones which confirm the proposed designed methodology. The proposed monopole antenna has a patch size of 13.5 mm × 6.5 mm and the whole antenna size (including the feed line) is 35 mm × 32 mm. Compared to conventional single-band microstrip patch radiator size, the proposed quad band radiator has the size of 9, 15, 37.5, and 72.5% at relevant frequency bands.

Screen-printed graphene is integrated with multiple-input multiple-output (MIMO) technology to conquer the most concerned surge in electronic waste caused by the mass deployment of Internet of things (IoT) applications. A flexible MIMO antenna is implemented with simple fabrication process suitable for large-scale production by screen printing graphene highly conductive ink on paper substrate, ensuring high-speed 5G mass data wireless transmission without damaging the ecological environment. This environmental-friendly, low-cost, flexible and conformal MIMO antenna with orthogonal polarization diversity employs co-planar waveguide feed and planar pattern for achieving high space utilization and better integration in most scenarios, for instance, body centric networks and monitoring systems. Excellent performance has been achieved due to the high conductivity of the graphene: the fabricated antenna exhibits an average sheet resistance of 1.9 Ω s q − 1 . The bandwidth of the antenna ranges from 2.22 GHz to 3.85 GHz (53.71% fractional bandwidth), covering 4 G long term evolution, sub-6 GHz 5 G mobile communication networks, 2.5 and 3.5 GHz WiMAX, and 2.4 and 3.6 GHz WLAN. Within this range, the antenna exhibits effective radiation, also its envelope correlation coefficient remains below 0.2 × 10 − 6 , manifesting outstanding signal transmission quality in a variety of wireless networks. This work illustrates a novel aggregation of MIMO technology and graphene printing electronics, enabling cheap accessible and green MIMO antennas to be massively integrated in IoT applications.