Flexible Dielectric Substrate Research Articles

Design of Flexible 3.2 GHz Rectangular Microstrip Patch Antenna for S-Band Communication

This paper presents the design, simulation, realization and analysis of flexible microstrip patch antenna for S-band applications. The proposed design also adopts the conformal structure by utilizing flexible substrate. Conformal or flexible structure allows the antenna to fit with any specified shape as desired. The antenna patch dimensions is 43 mm × 25 mm without SMA connector. The patch is etched on the flexible dielectric substrate, pyralux FR 9111, with a relative dielectric constant of εr = 3 and the thickness of substrate, h = 0.025 mm. The antenna is designed to resonate at 3.2 GHz. The return loss (RL) of the simulation is -35.80 dB at the center frequency of 3.2 GHz. The fabricated antenna prototype was measured at different bending angles scenarios including 0º, 30º, 60º, and 90º. The measurement of antenna prototype shows that the center frequency is shifted to the higher frequency of 3.29 GHz, compared to the simulation result. Among these scenarios, measurement at bending angle of 90º gives the best performance with RL = - 31.38 dB at 3.29 GHz, the bandwidth is 80 MHz, and the impedance ZA = 48.36 + j2.04 Ω. Despite a slight differences from simulation results, the designed antenna still performs well as expected.

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.

Inset-fed Multiband Square Patch Antenna on Flexible substrate for Fifth-Generation Wireless Communication

Purpose: Over a decade, the antenna has sparked considerable interest in the 5G frequency band in the wireless domain (covering industrial applications, home automation and mobile communication) because of its numerous advantages like compact, conformal to surfaces, easily integrated with the devices, etc. In general, an Antenna can be defined as a conductor which is exposed to space operable for a specific application. The purpose of the study is to design the Slotted patch antenna for 5G applications on a flexible dielectric substrate material which makes the antenna compact in its design aspect. Design/Methodology/Approach: Initially, the antenna design is carried out using the theoretical framework based on the available equations. The microwave studio software - Computer Simulation Technology (CST) is used to create and model the different antennas. Findings/Result: Based on the simulated models, the slotted patch antenna design 5 has 2 bands namely: 3.25 GHz, the return loss is -17.47 dB, and 5.89GHz, the return loss is -21.37dB. Whereas design 6 has 4 resonant bands measured at 2.04 GHz, the return loss (RL) is -11.68 dB, at 5.80GHz, the RL is -22.36 dB, at 7.14 GHz, the RL is -28.71 dB and at 8.83 GHz, the RL is -13.36 dB. The maximum bandwidth achieved for slotted patch antenna design 5 is 5% and the maximum bandwidth achieved for slotted patch antenna design 6 is 8%. Whereas the design of Multi slotted patch antenna flexible substrate design 7 and design 8 has the maximum achieved bandwidth of 10 %. Originality/Value: The design of slotted patch and multi slotted patch antenna using inset feed method on a flexible substrate for 5G frequency band. Paper Type: Design based Research Analysis.

Bioplastics and Carbon-Based Sustainable Materials, Components, and Devices: Toward Green Electronics.

The continuously growing number of short-life electronics equipment inherently results in a massive amount of problematic waste, which poses risks of environmental pollution, endangers human health, and causes socioeconomic problems. Hence, to mitigate these negative impacts, it is our common interest to substitute conventional materials (polymers and metals) used in electronics devices with their environmentally benign renewable counterparts, wherever possible, while considering the aspects of functionality, manufacturability, and cost. To support such an effort, in this study, we explore the use of biodegradable bioplastics, such as polylactic acid (PLA), its blends with polyhydroxybutyrate (PHB) and composites with pyrolyzed lignin (PL), and multiwalled carbon nanotubes (MWCNTs), in conjunction with processes typical in the fabrication of electronics components, including plasma treatment, dip coating, inkjet and screen printing, as well as hot mixing, extrusion, and molding. We show that after a short argon plasma treatment of the surface of hot-blown PLA-PHB blend films, percolating networks of single-walled carbon nanotubes (SWCNTs) having sheet resistance well below 1 kΩ/□ can be deposited by dip coating to make electrode plates of capacitive touch sensors. We also demonstrate that the bioplastic films, as flexible dielectric substrates, are suitable for depositing conductive micropatterns of SWCNTs and Ag (1 kΩ/□ and 1 Ω/□, respectively) by means of inkjet and screen printing, with potential in printed circuit board applications. In addition, we exemplify compounded and molded composites of PLA with PL and MWCNTs as excellent candidates for electromagnetic interference shielding materials in the K-band radio frequencies (18.0–26.5 GHz) with shielding effectiveness of up to 40 and 46 dB, respectively.

Flexible Wearable Composite Antennas for Global Wireless Communication Systems.

Although wearable antennas have made great progress in recent years, how to design high-performance antennas suitable for most wireless communication systems has always been the direction of RF workers. In this paper, a new approach for the design and manufacture of a compact, low-profile, broadband, omni-directional and conformal antenna is presented, including the use of a customized flexible dielectric substrate with high permittivity and low loss tangent to realize the compact sensing antenna. Poly-di-methyl-siloxane (PDMS) is doped a certain proportion of aluminum trioxide (Al2O3) and Poly-tetra-fluoro-ethylene (PTFE) to investigate the effect of dielectric constant and loss tangent. Through a large number of comparative experiments, data on different doping ratios show that the new doped materials are flexible enough to increase dielectric constant, reduce loss tangent and significantly improve the load resistance capacity. The antenna is configured with a multisection microstrip stepped impedance resonator structure (SIR) to expand the bandwidth. The measured reflection return loss (S11) showed an operating frequency band from 0.99 to 9.41 GHz, with a band ratio of 146%. The antenna covers two important frequency bands, 1.71–2.484 GHz (personal communication system and wireless body area network (WBAN) systems) and 5.15–5.825 GHz (wireless local area network-WLAN)]. It also passed the SAR test for human safety. Therefore, the proposed antenna offers a good chance for full coverage of WLAN and large-scale development of wearable products. It also has potential applications in communication systems, wireless energy acquisition systems and other wireless systems.

Polarization-independent multiband double-negative metamaterial through ferrite-based flexible substrate with tunable microwave dielectric properties

Microwave flexible dielectric materials offer a new set of attractive applications for modern devices as well as for metamaterial research and technology. In this article, metamaterials with double-negative characteristics fabricated on a novel flexible dielectric substrate are presented. These novel flexible microwave substrates were prepared from Mg-Zn ferrite powder. The proposed flexible metamaterials offer double-negative (DNG) properties, polarization insensitivity, and a higher effective medium ratio (EMR) for multiple bands of application. The prepared, flexible substrates exhibit performance superior to commercial materials with tunable dielectric properties, and the proposed metamaterial structure enhances the antenna performances as well. The flexible substrates are synthesized from Mg-Zn ferrite having two different molecular compositions of Mg denoted as Mg40 and Mg60. The prepared, highly flexible, and lightweight magnesium zinc ferrites of Mg40 and Mg60 possess tunable dielectric properties with relative dielectric permittivity of 5.18 and 4.20 and dielectric loss tangents of 0.004 and 0.006, respectively. The double-negative (DNG) metamaterial behavior is observed with the fabricated flexible metamaterials at 2.92 GHz, 4.42 GHz, 7.75 GHz, and 9.84 GHz for Mg40 and 3.16 GHz, 4.71 GHz, 8.21 GHz, and 10.52 GHz for Mg60 and validated by using 3D electromagnetic Simulator CST (Computer Simulation Technology) Microwave Studio and ADS (Advanced Design System) software. Therefore, the prepared, flexible metamaterials having improved EMR, polarization insensitivity, and DNG properties on a MgZnFe2O4substrate are suitable additions to the field of the flexible microwave.

A compact triple‐band metamaterial‐inspired antenna for wearable applications

AbstractA low‐profile (28 mm × 32 mm × 0.394 mm), metamaterial‐inspired antenna employing an array of 3 × 5 Hilbert‐shaped unit radiators printed on the upper side of a flexible dielectric substrate while the lower side contains a partial‐ground plane and the rest consists of a periodic square‐slotted ground plane is presented for wearable wireless devices covering Long‐Term Evolution (LTE), Long Term Evolution‐Advanced (LTE‐A), Wireless Local Area Network (WLAN), and Worldwide Interoperability for Microwave Access (WiMAX) bands. The antenna provides steerable radiation patterns for frequencies ranging from 3.3 to 3.9 GHz and a directive end‐fire radiation in the 5.8 GHz band. At 2.45 GHz, the antenna allows short‐range communications between a wearable sensor and handheld wireless device or a nearby base station. Two prototypes are fabricated; the first using traditional wet etching with copper; the second using inkjet printing with silver nano‐particles (SNPs) as the conducting material. We provide a systematic design procedure and a new physical insight into the operation of the antenna, in particular the end‐fire radiation patterns, which is based on the anisotropic dispersion characteristics of the radiating structure along the length axis leading to different effective electrical length to width ratios within the stopband. The realized gain varies from 0 to 2.5 dBi for frequencies ranging from 3.3 to 3.9 GHz where the 3‐dB beamwidth varies from 110° to 140° and the boresight is steered from 0° to 80°. The maximum realized gain varies from 4.75 to 4.5 dBi over the frequency range from 4.4 to 6 GHz, with slight change in the beamwidth and main lobe direction. Experimental measurements for the SNP prototype are reported in air and on a standard phantom model.

Compact Unidirectional Conformal Antenna Based on Flexible High-Permittivity Custom-Made Substrate for Wearable Wideband Electromagnetic Head Imaging System

An approach toward designing and building of a compact, low-profile, wideband, unidirectional, and conformal imaging antenna for electromagnetic (EM) head imaging systems is presented. The approach includes the realization of a custom-made flexible high-permittivity dielectric substrate to achieve a compact sensing antenna. The developed composite substrate is built using silicon-based poly-di-methyl-siloxane (PDMS) matrix and microscale of aluminium oxide (Al2O3) and graphite (G) powders. Al2O3 and G powders are used as fillers with different weight-ratio to manipulate and control the dielectric properties of the substrate for attaining better matched with the human head and reducing antenna’s physical size while keeping the PDMS flexibility feature. Using the custom-made substrate, a compact, wideband, and unidirectional on-body matched antenna for wearable EM head imaging system is realized. The antenna is configured as a multi-slot planar structure with four shorting pins, working as electric and magnetic dipoles at different frequency bands. The measured reflection coefficient (S11) shows an operating frequency band of 1–4.3 GHz. The time-average power density and the amplitude of the received signal inside the MRI-based realistic head phantom demonstrate a unidirectional propagation and high-fidelity factor (FF) of more than 90%. An array of 13 antennas are fabricated and tested on a realistic 3-D head phantom to verify the imaging capability of the proposed antenna. The reconstructed images of different targets inside the head phantom demonstrate the possibility of utilizing the conformal antenna arrays to detect and locate abnormality inside the brain using multistatic delay-multiply-and-sum beamforming algorithm.

A Multifunctional Reconfigurable Frequency-Selective Surface Using Liquid-Metal Alloy

This communication describes a miniaturized reconfigurable frequency-selective surface (FSS) that incorporates a liquid-metal alloy injected into an elastomer. The structure comprises a meandered pattern engraved on a flexible dielectric substrate, where the liquid metal [eutectic gallium indium (EGaIn)] adopts the geometry of the microfluidic channels. The novelty of the proposed design lies in its multifunctional response, switching from all-pass to bandpass/bandstop characteristic, depending on whether EGaIn is injected in the microchannels. The liquid-metal-filled structure, being asymmetric in nature, selectively realizes bandpass operation for a specific polarization, whereas bandstop response is observed under orthogonal polarization. Furthermore, the design exhibits miniaturization performance during bandpass response (at 1.37 GHz), corresponding to unit cell dimensions of $0.059\lambda _{0} \times 0.059\lambda _{0}$ . The structure was analyzed through the derivation of equivalent circuit models and several parametric variations. Finally, the proposed multifunctional FSS was fabricated by laser etching, and the filter parameters were experimentally verified under normal as well as oblique incidence.

Beamwidth Control of Omnidirectional Antenna Using Conformal Frequency Selective Surface of Different Curvatures

Development and implementation of different curvatures of a conformal frequency selective surface (FSS) for achieving beam diversity in a dual-band monopole antenna are demonstrated. The FSS based on a flexible dielectric substrate (polymer) is reflective at 3.5 GHz. The curved FSS when incorporated in the antenna gives different beamwidths (3 dB) between 68°–130° for concave shape and 144°–210° for convex shape at 3.5 GHz. In both the cases, omnidirectional radiation from the antenna is maintained at 5.8 GHz. Later, a corner reflector based on the FSS instead of a metal, operating at 5.8 GHz, is integrated in the antenna along with the convex shaped curved FSS. The new antenna system exhibits a beamwidth of 190° with a peak gain of 6.8 dBi at 3.5 GHz and the beamwidth of 58° with a peak gain of 8.3 dBi at 5.8 GHz. The proposed method is useful for achieving beam diversity in multiband antennas. Simulation results from ANSYS HFSS and experimental measurements of the fabricated prototypes are provided.

A temperature-activated nanocomposite metamaterial absorber with a wide tunability

Novel thin and flexible broadband electromagnetic microwave absorbers are realized with nanocomposites and achieve a wide frequency tunability (from 10 to 17.2 GHz) by actively adjusting the resistance. The proposed absorbers are fabricated by scalable screen printing of optimized nanoparticle ink onto the flexible dielectric composite substrates. Based on the shape memory effects of the substrate and piezoresistive effect of the nanocomposite frequency selective surface, a controllable sheet resistance, and thereby tunable wave absorption performance, can be realized in a temperature-activated and dynamically stable manner. The results provide new dimensions for the design of active electromagnetic devices by utilizing previously underestimated intrinsic properties of the artificial materials and the smart behavior of polymer-based nanocomposites.

Near-Field Chipless-RFID System With High Data Capacity for Security and Authentication Applications

A high data capacity chipless radio frequency identification (chipless-RFID) system, useful for security and authentication applications, is presented in this paper. Reading is based on the near-field coupling between the tag, a chain of identical split-ring resonators (SRRs) printed on a (typically flexible) dielectric substrate (e.g., liquid crystal polymer, plastic, and paper), and the reader. Encoding is achieved by the presence or absence of SRRs at predefined (equidistant) positions in the chain, and tag identification (ID) is based on sequential bit reading. Namely, the tag must be longitudinally displaced, at short distance, over the reader, a microstrip line loaded with an SRR and fed by a harmonic signal. By this means, the harmonic signal is amplitude modulated, and the (ID) code is contained in the envelope function, which can be obtained by means of an envelope detector. With this system, tag reading requires proximity with the reader, but this is not an issue in many applications within the domain of security and authentication (e.g., secure paper for corporate documents and certificates). Several circularly shaped 40-bit encoders (implemented in a commercial microwave substrate), and the corresponding reader, are designed and fabricated as proof-of-concept demonstrators. Strategies for programming the tags and a first proof-of-concept chipless-RFID tag fabricated on plastic substrate through inkjet printing are included in this paper.

A Flexible Metamaterial Terahertz Perfect Absorber

We designed a THz matematerial absorber using metallic wires (MWs) and split resonant rings (SRRs). This matematerial absorber exhibits perfect absorption which up to 96% at 4.03 THz and is capable of wrapped around objects because of flexible polyimide dielectric substrate.

Multiphysics Performance Evaluation of Flexible Substrate Based 1.2kV SiC Half Bridge Intelligent Power Module with Stacked Dies

Abstract Wide Bandgap (WBG) power devices have become the most promising solution for power conversion systems, with the best trade-off between theoretical characteristics, real commercial availability and maturity of fabrications. Advanced packaging technology is being heavily developed to take full advantages of WBG devices, in terms of materials, mechanical design, fabrication and electrical performance optimizations. In this paper, a flexible substrate based 1.2kV SiC Half Bridge Intelligent Power Module with stacked dies is introduced. The module design is based on the concept “Power Supply in Package (PSiP)”, high functionality is integrated in the module. Together with power stages, gate driver circuits, Low Dropout Regulators (LDO), digital isolators, and bootstrap circuits are integrated in the module. An ultra-thin flexible epoxy-resin based dielectric is applied in the module as substrates, its thickness can be as low as 80μm, with 8W/mK thermal conductivity. The SiC switches are double-side solderable, with copper as topside metallization on pads. No bonding wires are applied in the SiC PSiP module. The highside and lowside SiC switches on the phase leg is stacked vertically for interconnections with low parasitic and high denstiy. This work mainly addresses performance evaluation of the PSiP SiC half bridge module by multiphysics simulations. Q3D is employed to evaluate the parasitic inductance and resistance in the module, showing that parasitic inductance is lower than 1.5nH in the design. The extracted parasitics is imported in spice circuit model, simulation results show limited ringing during switching transients. Thermal simulations are employed to compare junction temperature of power modules with DBC subtrates and flexible substrates, then to evaluate the thermal performance of the designed PSiP SiC model with stacked dies. It shows that junction temperature of designed IPM is higher than regular module at same condition. The paper also provides guideline for optimized heat sink design to lower junction temperature of the SiC IPM. Mechanical simulations are employed to evaluate the pre-stress induced in modules with DBC substrate and flexible dielectric substrate, and proves that mechanical stress induced by reflowing process can be reduced significantly by using ultra-thin flexible dielectric as substrate.

Strongly Confined Spoof Surface Plasmon Polaritons Waveguiding Enabled by Planar Staggered Plasmonic Waveguides.

We demonstrate a novel route to achieving highly efficient and strongly confined spoof surface plasmon polaritons (SPPs) waveguides at subwavelength scale enabled by planar staggered plasmonic waveguides (PSPWs). The structure of these new waveguides consists of an ultrathin metallic strip with periodic subwavelength staggered double groove arrays supported by a flexible dielectric substrate, leading to unique staggered EM coupling and waveguiding phenomenon. The spoof SPP propagation properties, including dispersion relations and near field distributions, are numerically investigated. Furthermore, broadband coplanar waveguide (CPW) to planar staggered plasmonic waveguide (PSPW) transitions are designed to achieve smooth momentum matching and highly efficient spoof SPP mode conversion. By applying these transitions, a CPW-PSPW-CPW structure is designed, fabricated and measured to verify the PSPW’s propagation performance at microwave frequencies. The investigation results show the proposed PSPWs have excellent performance of deep subwavelength spoof SPPs confinement, long propagation length and low bend loss, as well as great design flexibility to engineer the propagation properties by adjusting their geometry dimensions and material parameters. Our work opens up a new avenue for development of various advanced planar integrated plasmonic devices and circuits in microwave and terahertz regimes.

Ultra-wideband filtering of spoof surface plasmon polaritons using deep subwavelength planar structures.

Novel ultra-wideband filtering of spoof surface plasmon polaritons (SPPs) is proposed in the microwave frequency using deep subwavelength planar structures printed on thin and flexible dielectric substrate. The proposed planar SPPs waveguide is composed of two mirror-oriented metallic corrugated strips, which are further decorated with parallel-arranged slots in the main corrugated strips. This compound structure provides deep subwavelength field confinement as well as flexible parameters when employed as a plasmonic waveguide, which is potential to construct miniaturization. Using momentum and impedance matching technology, we achieve a smooth conversion between the proposed SPPs waveguide and the conventional transmission line. To verify the validity of the design, we fabricate a spoof SPPs filter, and the measured results illustrate excellent performance, in which the reflection coefficient is less than −10 dB within the −3 dB passband from 1.21 GHz to 7.21 GHz with the smallest insertion loss of 1.23 dB at 2.21 GHz, having very good agreements with numerical simulations. The ultra-wideband filter with low insertion loss and high transmission efficiency possesses great potential in modern communication systems.

Sol–gel synthesis of transition-metal doped ferrite compounds with potential flexible, dielectric and electromagnetic properties

A compact and flexible dielectric substrate with efficient electromagnetic performances both in flat and bending conditions are presented in this paper.

Thermophysical Properties in Assembling Process at Macro and Micro Level

The electronic modules are complex ensemble of electronic components having terminals (PIN) connected by solder joints on dedicated metallic surfaces (PAD) parts of conductive interconnection structure realized on rigid or flexible dielectric substrate having different core materials. The reliability of the electronic modules could be considered as expression of solder joints functionality (SJF) relating to working conditions and unique defined by their electrical, mechanical and thermal properties. These properties are in close connection with the solder joints microstructures, result of the soldering Process temperature gradient action over the trinomial solder alloy Paste, Pin and Pad. Consequently the solder joints quality can be correctly evaluated taking into consideration not only the severally intrinsic parameters of the trinomial elements Pin-Pad-Paste characterized by specific thermophysical properties (ThP), but also interrelate the complex reaction at the interface between them and interdependence with the soldering Process parameters.In the paper, will be analyzed the influencing factors of manufacturing processes, the most important assembling defects at macro and micro level, their causes relating to specific ThP and processes at interfaces Pin-solder joints-Pad, it will be identify the Key Process Input Variables (KPIV) and propose a structural model for assembling processes, 4P Soldering Model, as an useful tool in engineering of electronic product in order to assure the assumed goal for assembling stage.

A multiband THz bandpass filter based on multiple-resonance excitation of a composite metamaterial

We present a systematic numerical study on a metal-dielectric-metal (MDM) sandwich structure for multiple resonance transmission in terahertz (THz) region. The designed structure consists of periodic square close ring array on both side of a flexible dielectric substrate, exhibits a multiband transmission, with low average insertion loss, steep skirts and high out-of-band rejection. In addition, due to its rotationally symmetric structure, this filter is polarization-insensitive for normal incidence of the electromagnetic waves, keeping highly transmission at a wide range of incident angles for transverse electric waves and transverse magnetic waves. The metamaterial structure can be utilized as a desirable multiband filter with many practical applications, especially for THz communication, spectroscopic detection and phase imaging.

A Conformal Conical Archimedean Spiral Antenna for UWB Communications

In this paper, a wide-band miniaturized Conformal conical Archimedean spiral (CCARS) antenna is proposed for Ultra wideband (UWB) communications. The CCARS antenna utilizes the vertical space instead of horizontal space significantly saving the antenna installation space. We investigate the transformation from Planar Archimedean spiral (PARS) antenna to the CCARS antenna and the antenna miniaturization technique. Due to the using of flexible dielectric substrate, the PARS antenna can be bent freely, which assures the transformation from the PARS antenna to the CCARS antenna. To realize antenna miniaturization, zigzag shape arms are applied to the PARS antenna. Moreover, the CCARS antenna has good unidirectional radiation property that avoids the using of traditional absorber-loaded back cavity. The measured results of antenna prototype indicate that the Voltage standing wave ratio (VSWR) is below 2 over the frequency range from 1.3GHz to 9GHz. The antenna gain is higher than 3.4dBi and the Front to back (F/B) ratio is better than 20dB from 2GHz to 7GHz. In addition, good radiation patterns and broad 3dB beam width are also available for the CCARS antenna.