Tattoo Antenna Temporary Transfers Operating On-Skin (TATTOOS)

This paper discusses the development of RFID logo antennas based on the logos of Loughborough University and the University of Kent which can be tattooed directly onto the skin’s surface. Hence, this paper uses aesthetic principles to create functional wearable technology. Simulations of possible designs for the tattoo tags have been carried out to optimize their performance. Prototypes of the tag designs were fabricated and read range measurements with the transfer tattoos on a volunteers arm were carried out to test the performance. Measured Read ranges of approximately 0.5 m have been achieved with the antenna 10 µm from the body

Fully fabric knitted antennas for wearable electronics

The worldwide wearable technology market is expected to exceed $6B by 2016 and wearable antennas will be used by the emergency services, fashion designers, military, athletes and patients. Exploring different methods of fabricating antennas is important especially as user comfort and aesthetics are key considerations in ensuring mainstream acceptance. Previously the authors have examined embroidered antennas using highly conductive threads [Chauraya et al. EuCAP 2012]. Please see this paper for a detailed literature review of wearable antennas. In this paper, we examine knitting as a technique of fabricating antennas. These antennas were fully fabric with a knitted ground plane, a knitted substrate and a knitted patch element. They were fabricated using industrial knitting machinery and hence could potentially be scaled up to mass-manufacture. Four different versions were considered (all had a knitted ground plane and substrate): i) a conducting coated nylon fabric (Nora Dell); ii) a knitted patch with a high fiber density (Sample 1); iii) a knitted patch with a medium fiber density (Sample 2) and iv) a knitted patch with a coarse fiber density (Sample 3). The resulting antennas were extremely flexible and soft to the touch. The return loss results are shown in the figure. All the antennas were fed with a probe feed positioned the same distance from the edge of the patch - the magnitude of the return loss could be improved by finding the optimal feeding point. The S11 and associated bandwidth results of the antennas suggests that the Nora Dell antenna exhibits the smallest losses. The results also indicate that the losses of the knitted antennas improve as the knitted patches became denser. The presentation will include measured radiation patterns, efficiency results and an in-depth analysis of the strengths and weaknesses of this manufacturing technique

Addressing the challenges of fabricating microwave antennas using conductive threads

This paper examines the advantages and challenges of creating microwave patch antennas using conducting threads. The antennas are produced using automated embroidery machinery that could be easily scaled up to mass manufacture. Textile patch antennas are designed that resonate between 2 and 2.7GHz depending on the substrate. Different stitch directions and compositions were considered. Measured gain and efficiency results are included in this paper

SAR Levels for Irradiation by a Crumpled 900 MHz Flexible Diamond Dipole

In this work, the antenna performance and Specific Absorption Rate (SAR) levels in a homogeneous phantom exposed to 900 MHz flexible diamond dipole antenna are investigated under different crumpling deformation conditions. The numerical simulations of the realistic complex two dimensional crumpling are performed by using Finite Integration Technique (FIT) which is applied in Computer Simulation Technology (CST) Microwave Studio. The validation of results with the industry standard DASY4 robot SAR measurement system is made possible with the use of homogenous phantom model. The 1 g, 10 g and point SAR are enhanced by 28.33 %, 36.75 % and 9.55 % respectively due to the antenna crumpling deformation. The short length ripple investigated in this paper shows the highest relative SAR increment

Ball grid array-module with integrated shaped lens for WiGig applications in eyewear devices

A ball grid array-module (BGA-module) incorporating a low-cost shaped dielectric lens is proposed for wireless communications in the 60-GHz WiGig band between a smart eye-wear, where it is integrated and facing a laptop or TV. The module, which is codesigned with a 60-GHz transceiver, consists of two separate identical antennas for transmitting (Tx) and receiving (Rx). The in-plane separation of these elements is 6.9 mm both being offset from the lens focus. This poses a challenge to the lens design to ensure coincident beam pointing directions for Rx and Tx. The shaped lens is further required to narrow the angular coverage in the elevation plane and broaden it in the horizontal plane. A 3-D-printed eyewear frame with an integrated lens and a recess for proper BGA-module integration is fabricated in ABS-plastic material. Measurements show a reflection coefficient below -12 dB in the 57-66 GHz band. A maximum gain of 11 dBi is obtained at 60 GHz, with 24 degrees and 96 degrees beamwidth at 5-dBi gain, respectively, in the vertical and horizontal planes. The radiation exposure is evaluated for a homogeneous SAM head phantom and a heterogeneous visible human head. The simulated power density values for both models are found to be lower than the existing standards

Multi-material additive manufacture and microwave-assisted sintering of a metal/ceramic metamaterial antenna structure

Multi-material metal/ceramic 3D structures comprising of metallic silver and ultra-low sintering temperature silver molybdenum oxide ceramics, have been additively manufactured and hybrid densified using microwave-assisted sintering for the first time. Optimum densification conditions at 440 °C / 1 h, resulted in relative permittivity, εr = 10.99 ± 0.04, dielectric losses, tanδ = 0.005 ± 0.001 and microwave quality factor, Q × f = 2597 ± 540 GHz. Applying 2 kW microwave energy at 2.45 GHz for 60 min, was proven sufficient, to densify the metallic Ag infilling electrodes, without causing any macroscopic defects. A fully functional multi-layered antenna structure with a metamaterial artificial magnetic conductor was designed, dual-printed and densified, to showcase the potential of combining multi-material additive manufacturing with microwave-assisted sintering

Microwave backscatter enhancement using radial anisotropy in biomimetic core-shell spheres

This is the final version. Available on open access from the American Institute of Physics via the DOI in this record.Data availability: The data that support the findings of this study are available from the corresponding authors upon reasonable request.Enhanced backscattering of microwave radiation is demonstrated experimentally in a biomimetic radially anisotropic spherical metamaterial component. The core-shell device replicates the optical function of nanospheres observed in the tapetum reflector of the compound eye of the shrimp Litopenaeus vannamei (Boone, 1931) and translates the effect from the optical domain to microwave frequencies. Analytical Mie theory calculations and numerical-method simulations are used to describe the origin of the observed scattering from a single dielectric sphere in terms of its multipolar Mie resonances. The fabrication of components using additive manufacture and their experimental characterization are described. The results show that the introduction of radial anisotropy in the shell more than doubles the monostatic radar cross section compared to the equivalent isotropic case. This work represents a practical demonstration of a synthetic bio-inspired structure, harnessing performance-enhancing adaptations that have evolved in nature. The results augment the range of techniques available for the control of electromagnetic scattering with relevance to applications in the manipulation of radar return signals.Engineering and Physical Sciences Research Council (EPSRC)Royal Academy of Engineerin

Multi-material additive manufacturing of low sintering temperature Bi2Mo2O9 ceramics with Ag floating electrodes by selective laser burnout

Additive manufacturing (AM) of co-fired low temperature ceramics offers a unique route for fabrication of novel 3D radio frequency (RF) and microwave communication components, embedded electronics and sensors. This paper describes the first-ever direct 3D printing of low temperature co-fired ceramics/floating electrode 3D structures. Slurry-based AM and selective laser burnout (SLB) were used to fabricate bulk dielectric, Bi2Mo2O9 (BMO, sintering temperature = 620–650°C, εr = 38) with silver (Ag) internal floating electrodes. A printable BMO slurry was developed and the SLB optimised to improve edge definition and burn out the binder without damaging the ceramic. The SLB increased the green strength needed for shape retention, produced crack-free parts and prevented Ag leaching into the ceramic during co-firing. The green parts were sintered after SLB in a conventional furnace at 645°C for 4 h and achieved 94.5% density, compressive strength of 4097 MPa, a relative permittivity (εr) of 33.8 and a loss tangent (tan δ) of 0.0004 (8 GHz) for BMO. The feasibility of using SLB followed by a post-printing sintering step to create BMO/Ag 3D structures was thus demonstrated

Cold sintered CaTiO3-K2MoO4 microwave dielectric ceramics for integrated microstrip patch antennas

CaTiO3-K2MoO4 (CTO-KMO) dielectric composites were successfully cold-sintered at 150 °C for 30 min with a uniaxial pressure of 200 MPa. X-ray diffraction, Raman spectroscopy, back-scattered SEM and energy dispersive x-ray mapping confirmed the coexistence of CTO and KMO with no evidence of interdiffusion and parasitic phases either between the two ceramic end-members or with Ag internal electrodes. As KMO concentration increased, the temperature coefficient of resonant frequency (TCF) and relative pemittivity (εr) decreased but the microwave quality factor (Q × f) increased. A near-zero TCF composition was obtained for CTO-0.92KMO composites which exhibited εr ∼ 8.5 and Q × f ∼ 11,000 GHz. A microstrip patch antenna was designed and fabricated using cold sintered CTO-0.92KMO as a substrate (40×40×1.4 mm), which gave a s11 of −14.2 dB and a radiation efficiency of 62.0 % at 2.51 GHz

Temperature stable cold sintered (Bi0.95Li0.05)(V0.9Mo0.1)O4-Na2Mo2O7 microwave dielectric composites

Dense (Bi0.95Li0.05)(V0.9Mo0.1)O4-Na2Mo2O7 (100−x) wt.% (Bi0.95Li0.05)(V0.9Mo0.1)O4 (BLVMO)-x wt.% Na2Mo2O7 (NMO) composite ceramics were successfully fabricated through cold sintering at 150 °C under at 200 MPa for 30 min. X-ray diffraction, back-scattered scanning electron microscopy, and Raman spectroscopy not only corroborated the coexistence of BLVMO and NMO phases in all samples, but also the absence of parasitic phases and interdiffusion. With increasing NMO concentration, the relative pemittivity (εr) and the Temperature Coefficient of resonant Frequency (TCF) decreased, whereas the Microwave Quality Factor (Qf) increased. Near-zero TCF was measured for BLVMO-20wt.%NMO composites which exhibited εr ~ 40 and Qf ~ 4000 GHz. Finally, a dielectric Graded Radial INdex (GRIN) lens was simulated using the range of εr in the BLVMO-NMO system, which predicted a 70% aperture efficiency at 26 GHz, ideal for 5G applications