Wayne S. T. Rowe

Elastomeric silicone substrates for terahertz fishnet metamaterials

In this work, we characterize the electromagnetic properties of polydimethylsiloxane(PDMS) and use this as a free-standing substrate for the realization of flexible fishnet metamaterials at terahertz frequencies. Across the 0.2–2.5 THz band, the refractive index and absorption coefficient of PDMS are estimated as 1.55 and 0–22 cm−1, respectively. Electromagnetic modeling, multi-layer flexible electronics microfabrication, and terahertz time-domain spectroscopy are used in the design, fabrication, and characterization of the metamaterials, respectively. The properties of PDMS add a degree of freedom to terahertz metamaterials, with the potential for tuning by elastic deformation or integrated microfluidics.

The Effect of Ply Orientation on the Performance of Antennas in or on Carbon Fiber Composites

In this paper, the anisotropic conductivity efiect of quasi- isotropic carbon flber laminates on conformal load-bearing antenna structures (CLAS) is presented. The conductivity of a quasi-isotropic IM7/977-3 CFRP laminate is measured using waveguide techniques. The results show that orientation of the surface ply relative to the polarization of the incident E-fleld has a major in∞uence on the re∞ectivity. This difierence is attributed to the fact that carbon flbres oriented parallel to the E-fleld plies behave as good conductors, while ofi-axis plies present as lossy dielectric layers with a flnite conductivity. This anisotropic behavior of the ply layers is shown to have a distinctive in∞uence on the operation of both microstrip patch and slot antennas.

Angularly Stable Frequency Selective Surface With Miniaturized Unit Cell

A new type of Frequency Selective Surface (FSS) with miniaturized resonator element is proposed. The FSS structure is shown to have a FSS unit cell dimension that is miniaturized to 0.067 λ0. Miniaturization of the FSS unit cell is achieved by coupling two meandered wire resonators separated by single thin substrate layer. The capacitance due to the small separation between the meandered wire elements results in a lowering of the resonant frequency. To demonstrate the validity of the design, the meandered wire resonator FSS was fabricated and tested using a free space measurement facility. The FSS produces a stable angular response up to 80 degrees for TE and TM incident angles.

Electromagnetic field intensity generated by partial discharge in high voltage insulating materials

Partial dischagre is the precursor of insulators breakdown. In this work the propagation of electromagnetic radiation emitted from partial discharge in high voltage insulating materials is investigated. Three common dielectric materials used in power industry: polymer, epoxy resin and ceramics are studied. The results obtained are envisaged to support the development of appropriate sensors for partial discharge detection. The radiation pattern is dependent on a multitude of parameters. Among these, the intensity distribution of the source as well as the dielectric material and its geometry are the main parameters. Signiflcant difierences in the radiation spectra are obtained for insulators made of ceramic material compare to non- ceramic insulators.

Multi-Service Highly Sensitive Rectifier for Enhanced RF Energy Scavenging

Due to the growing implications of energy costs and carbon footprints, the need to adopt inexpensive, green energy harvesting strategies are of paramount importance for the long-term conservation of the environment and the global economy. To address this, the feasibility of harvesting low power density ambient RF energy simultaneously from multiple sources is examined. A high efficiency multi-resonant rectifier is proposed, which operates at two frequency bands (478–496 and 852–869 MHz) and exhibits favorable impedance matching over a broad input power range (−40 to −10 dBm). Simulation and experimental results of input reflection coefficient and rectified output power are in excellent agreement, demonstrating the usefulness of this innovative low-power rectification technique. Measurement results indicate an effective efficiency of 54.3%, and an output DC voltage of 772.8 mV is achieved for a multi-tone input power of −10 dBm. Furthermore, the measured output DC power from harvesting RF energy from multiple services concurrently exhibits a 3.14 and 7.24 fold increase over single frequency rectification at 490 and 860 MHz respectively. Therefore, the proposed multi-service highly sensitive rectifier is a promising technique for providing a sustainable energy source for low power applications in urban environments.

A Reconfigurable FSS Using a Spring Resonator Element

Reconfigurable and tunable frequency selective surfaces (FSSs) are of significant interest in applications such as tunable radomes and adaptive screening of unwanted wireless transmissions. Conventional FSSs require additional bias circuitry to tune the operating frequency or to change its characteristics. In this letter, a new tuning technique using a spring resonator element is proposed. This technique can be applied to FSS design to make it reconfigurable and/or to fine-tune the response. The FSS frequency response can be adjusted by changing the spring height

A Planar Dual-Arm Equiangular Spiral Antenna

h

Elastomer-Based Pneumatic Switch for Radio Frequency Microdevices

with applied pressure. The functional characteristic of the FSS can also be altered between a bandstop and bandpass filter response. A parametric analysis of the novel spring FSS is undertaken in CST software, and the results are validated with experimental measurement .

Utilising microstrip patch antenna strain sensors for structural health monitoring

The design is described of a planar dual-arm equiangular spiral antenna incorporated with chip resistors inside the substrate. The chip resistors were applied to this equiangular spiral antenna to achieve 9:1 impedance bandwidth (2 to 18 GHz) with an extremely low profile structure. The simulated and measured magnitude of the reflection coefficient (S 11), gain, and measured radiation patterns are presented.

Theoretical investigation on the use of high permittivity materials in microstrip aperture stacked patch antennas

This paper reports the realization and characterization of a pneumatic microswitch integrated with a high-frequency radio frequency (RF) transmission line on an elastomer substrate. A process for the fabrication of low-loss RF coplanar transmission lines on flexible elastomeric polydimethylsiloxane (PDMS) substrates was developed, and devices realized using this process were used to determine the characteristics of PDMS as an RF substrate with uniform low loss and low dielectric constant being measured. To demonstrate the capabilities of this elastomer-based RF platform, a micromechanical switch exploiting a pneumatic membrane valve was integrated with the PDMS RF transmission line. Repeatable switching was observed with greater than 20-dB suppression in the “off” state and minimal degradation of the transmission line characteristics in the “on” state being achieved over a multioctave 2-20-GHz bandwidth. These valve-integrated transmission lines had an insertion loss of 0.16 dB·mm-1 at 20 GHz. This proof-of-concept device represents a novel combination of the areas of micropneumatics, flexible electronics, and broadband microwave devices with excellent RF properties, low interference, bias-free pneumatic switching, and relatively simple fabrication.