Patrick McEvoy

Microstrip-Fed Wideband Circularly Polarized Printed Antenna

A wideband circularly-polarized printed antenna is proposed, which employs an asymmetrical dipole and a slit in the ground plane which are fed by an L-shaped microstrip feedline using a via. The proposed antenna geometry is arranged so that the orthogonal surface currents, which are generated in the dipole, feedline and ground plane, have the appropriate phase to provide circular polarization. A parametric study of the key parameters is made and the mechanism for circular polarization is described. The measured results show that the impedance bandwidth is approximately 1.34 GHz (2.45 GHz to 3.79 GHz) and the 3 dB axial ratio bandwidth is approximately 770 MHz (2.88 GHz to 3.65 GHz) which represent fractional bandwidths of approximately 41% and 23%, respectively, with respect to a centre frequency of 3.3 GHz.

Integration of Microstrip Patch Antenna With Polycrystalline Silicon Solar Cell

The implementation of a polycrystalline silicon solar cell as a microwave groundplane in a low-profile, reduced-footprint microstrip patch antenna design for autonomous communication applications is reported. The effects on the antenna/solar performances due to the integration, different electrical conductivities in the silicon layer and variation in incident light intensity are investigated. The antenna sensitivity to the orientation of the anisotropic solar cell geometry is discussed.

Compact Patch Antenna for Electromagnetic Interaction With Human Tissue at 434 MHz

Single element loop, dipole and conventional square patch antennas have been used as hyperthermia applicators in the treatment of cancerous human cells at superficial depths inside the body. A smaller novel patch antenna in very close proximity to a phantom tissue model produces an enhanced specific absorption rate pattern without significant frequency detuning or impedance mismatch. The new patch increases its coupling aperture by supporting a combination of resonances that are also typical for loop, dipole and square patch antennas. For computation efficiency and clarity in the synthesized hyperthermia treatment conditions, simplified planar tri-layered tissue models interfaced with a water-bolus are used to study the permittivity loading on the antennas and the resultant specific absorption rates.

UWB Vivaldi antenna based on a spline geometry with frequency band-notch

A printed UWB Vivaldi antenna is presented in this paper. Its geometry is based on a novel spline shape and optimised by an efficient global optimisation algorithm. A U-shaped slot is introduced into the geometry to notch out the 5.1 GHz to 5.8 GHz WLAN band. This can be used to mitigate interference between WLAN and UWB systems.

Optimized Monopole and Dipole Antennas for UWB Asset Tag Location Systems

Miniaturized monopole and dipole antenna designs are reported with performances optimized for ultrawideband pulsed radio applications. The geometries are created using Bézier spline shapes, which have been refined with a genetic algorithm to simultaneously take account of both frequency- and time-domain criteria. Time-domain measurements of ultra wideband antennas with uniformly distributed energy across the full 3.1-10.6 GHz mask are reported for the first time and validate a new approach to minimization of pulse dispersion effects in the antenna designs.

Footwear Antennas for Body Area Telemetry

Antennas designed to link footwear sensors within body centric networks are introduced with two small UWB antennas, one directional and another quasi-omnidirectional. The radiating characteristics are evaluated for three positions on a sample sports shoe using a detailed simulation model and measurements with a homogenous foot phantom. Antenna performance is assessed for resilience to close proximity loading by the footwear materials and the phantom foot.

Antenna design considerations for high specific absorption rate in local hyperthermia treatment

The design of a miniaturised low-profile efficient hyperthermia applicator is presented. The efficiency is attributed to small size, resilience to detuning and wide bandwidth. The antenna provides a high value of SAR and is well matched to tissue, even at close distances.

Conformal UWB impulse antenna for pipe telemetry

The fidelity factor of a directional UWB antenna has been investigated for communicating telemetry data from a pipe that can contain liquids. The impedance match and the radiation patterns the antipodal Vivaldi design have been optimized for a 3.1–10.6 GHz bandwidth. The mechanical properties of the substrate material permit limited flexing and in this case, it is curved around the transverse axis of a 56 mm diameter pipe. An initial frequency domain analysis is extended with the study of a 7.5 GHz bandwidth pulse centred at 6.85 GHz. The fidelity factor of the antenna in a free-space environment was measured for comparison with the pipe-mounted setup. The proximity of the antenna and pipe is studied for signal degradation, as is the performance for empty and water-filled conditions.

Group delay performance of ultra wideband monopole antennas for communication applications

While limited in dimensions, the shape of small ultra wideband (UWB) antennas can significantly impact on the required gain pattern stablity and the inherent impulse spreading throughout the bandwidth. The comparative gain performance of a square monopole and two Bezier-spline shaped monopoles (optimised for low insertion losses on small groundplanes) as portable UWB device antennas solutions are reported. By measuring the transmission group delay for the three geometries in paired combinations, the time-domain spreading due to each individual antenna is solved numerically with a system of equations.

Amorphous Silicon Solar Vivaldi Antenna

An ultrawideband solar Vivaldi antenna is proposed. Cut from amorphous silicon cells, it maintains a peak power at 4.25 V, which overcomes a need for lossy power management components. The wireless communications device can yield solar energy or function as a rectenna for dual-source energy harvesting. The solar Vivaldi performs with 0.5-2.8 dBi gain from 0.95-2.45 GHz , and in rectenna mode, it covers three bands for wireless energy scavenging.