Development of Enhanced Range, High Q, Passive, Chipless RFID Tags for Continuous Monitoring and Sensing Applications

A high Q planar chipless RFID tag with high sensitivity is proposed for communication applications. In particular, the tag structure is composed of a complementary spiral structure (CSS) that is able to provide high sensitivity and compactness. A semi analytical formula for the design of a single bit tag is derived, and the behaviour of the CSS is analysed for different dielectric substrates. Different tags, composed of up to a set of eight resonators, have been numerically and experimentally assessed. In particular, a system prototype composed of a reader and a set of tags are fabricated and experimentally assessed as a proof of concept. The system provided an operative range of tens of centimetres (a maximum operative range of 65 cm). The obtained results are quite promising and the agreement between simulated and measured results are found to be good.

High-Efficiency Broadband Planar Array Antenna with Suspended Microstrip Slab for X-Band SAR Onboard Small Satellites

In this paper, a high efficiency broadband planar array antenna is developed at X-band for synthetic aperture radar (SAR) on small satellites. The antenna is based on a multi-layer element structure consisting of two dielectric substrates made of Taconic TLY-5 and three copper layers (i.e., the parasitic patch (top layer), the active patch (middle layer), and the ground plane (bottom layer)). The parasitic patch resides on the bottom surface of the upper TLY-5 substrate while the active patch is printed on the top surface of the lower substrate. A Rohacell foam material is sandwiched between the top layer and the middle layer to separate the two dielectric substrates in order to achieve high directivity, wideband, and to keep the antenna weight to a minimum as required by the SAR satellite application. To satisfy the required size of the antenna panel for the small SAR satellite, an asymmetric corporate feeding network (CFN) is designed to feed a 12 × 16 planar array antenna. However, it was determined that the first corporate feed junction at the center of the CFN, where higher amplitudes of the input signal are located, contributes significantly to the leaky wave emission, which degrades the radiation efficiency and increases the sidelobe level. Thus, a suspended microstrip slab, which is simply a wide and long microstrip line, is designed and positioned on the top layer directly above that feed junction to prevent the leaky waves from radiating. The experimental results of the antenna show good agreement with the simulated ones, achieving an impedance bandwidth of 12.4% from 9.01 to 10.20 GHz and a high gain above 28 dBi. The antenna efficiency estimated from the gain and directivity eclipses 51.34%.

Properties of Polysiloxane/Nanosilica Nanodielectrics for Wearable Electronic Devices

Polymer nanodielectrics characterized by good flexibility, processability, low dielectric loss and high dielectric permittivity are materials of interest for wearable electronic devices and intelligent textiles, and are highly in demand in robotics. In this study, an easily scalable and environmentally friendly method was applied to obtain polysiloxane/nanosilica nanocomposites with a large content of nanofiller, of up to 30% by weight. Nanosilica was dispersed both as individual particles and as agglomerates; in nanocomposites with a lower amount of filler, the former prevailed, and at over 20 wt% nanosilica the agglomerates predominated. An improvement of both the tensile strength and modulus was observed for nanocomposites with 5–15 wt% nanosilica, and a strong increase of the storage modulus was observed with the increase of nanofiller concentration. Furthermore, an increase of the storage modulus of up to seven times was observed in the nanocomposites with 30 wt% nanosilica. The tensile modulus was well fitted by models that consider the aggregation of nanoparticles and the role of the interface. The dielectric spectra showed an increase of the real part of the complex relative permittivity with 33% for 30 wt% nanosilica in nanocomposites at a frequency of 1 KHz, whereas the loss tangent values were lower than 0.02 for all tested nanodielectrics in the radio frequency range between 1 KHz and 1 MHz. The polysiloxane–nanosilica nanocomposites developed in this work showed good flexibility; however, they also showed increased stiffness along with a stronger dielectric response than the unfilled polysiloxane, which recommends them as dielectric substrates for wearable electronic devices.

Characterization of Graphenic Carbon Produced by Pulsed Laser Ablation of Sacrificial Carbon Tapes

This paper reports on the pulsed laser deposition of nanocarbon films on metal and dielectric substrates, using high-purity sacrificial carbon tape as a carbon source on a neutral gas background. The films were characterized by X-ray diffraction (XRD), photoelectron (XPS) and Raman spectroscopy. The XRD and Raman structural analyses revealed that the synthesized films have a graphenic nanocrystalline turbostratic structure, with sp2 clusters about 15–18 nm in size, depending on the laser fluence. A significant decrease in the oxygen and hydrogen contents in the films, in comparison with the target material, was established using XPS, as well as a significant decrease in the sp3 carbon content. The deposited films were found to be similar to reduced graphene oxide (rGO) in composition, with a surprisingly low number of defects in the sp2-matrix. The method proposed in the work may have good prospects of application in the production of energy storage and nonvolatile memory devices.

Comparison of Metallization Schemes on Glass Dielectrics for X-Band Glass Antennas and Energy Harvesting

We prepare and test four types of glass antennas for X-band applications and energy harvesting. These antennas are made of three different glass metallization schemes, including conductive copper foil (CCF), conductive silver paste (CSP) and indium tin oxide (ITO) thin film. Compared with conventional microstrip patch antennas, the dielectric substrate materials of these designs are replaced with silicon-boron glass (εr = 6, tangent δ = 0.002). The antenna with CCF as a radiator and ground plane (case one) is compared with the antenna with ITO replacing the radiator (case two) and ground plane (case three), respectively, and the glass antenna made of CSP (case four) is also presented. In this paper, these four types of glass antennas are measured and analyzed, and a comparison of the fabrication process and performance of these antennas is demonstrated. This study could contribute to the development of human-machine interactivity (HMI) systems with glass dielectric substrates.

Design of a Miniaturized Implantable PIFA with DGS for the Investigation of Uterus Fibroids

Continuous follow-up of unusual fibroids growth in the uterus is critical for minimizing the unwanted complexities of female’s certain health conditions. This article presents an implantable circular-shaped multi-facet PIFA for early detection of uterus fibroids. The radius of the circular antenna is 7.5 mm with the dimension of π × (7.5)2 × 1.58 mm3. The antenna has maximum return loss of 37 dB at 2.43 GHz, is suitable for ISM band use. Being low profile makes it entirely implantable in uterus. To expand the radiation efficiency and enhance the bandwidth two dielectric substrates of FR-4 and Rogers RO 3210 with each thickness of 0.79 mm are utilized. Top and bottom sides of the antenna have covered with Teflon to ensure biocompatibility. Defected ground structure has been used for size reduction as well as bandwidth increase. The performance of the antenna is also investigated in free space, biocompatible layer, and uterus layer. The estimated specific absorption rate is 0.36 W/kg when implanted in uterus.