Sergio Curto

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.

Groundplane Dependent Performance of Printed Antenna for MB-OFDM-UWB

A printed ultra wideband (UWB) antenna suitable for multiband orthogonal frequency division multiplexing (MB-OFDM) UWB is presented in this paper. The proposed antenna covers a wide band from 3.1 GHz to 11.2 GHz. Good performance and low cost production was obtained using FR-4 substrate. An examination of the effects of ground plane dimensions on antenna properties such as gain, bandwidth and radiation pattern is made.

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.

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.

Electromagnetic coupling mechanism in a layered human tissue model as reference for 434 MHz RF medical therapy applicators

In order to minimize exposure to human tissue, electromagnetic interaction with antennas has benefited from a lot of research since hand-held communication transceivers became widely used consumer products. On the other hand, medical applications have been exploiting the ISM (industrial scientific and medical standard) 434 MHz frequency band for therapeutic applications such as hyperthermia. Various antennas have been used in hyperthermia applicators but advanced designs depend on improved knowledge of the radiated antenna modes and interacting influence of human tissue. As a preliminary step towards analyzing antennas interacting with tissues in the near- and far-fields, this study reports on the coupling mechanism of a half-wavelength dipole at 434 MHz. This will provide an experimental method for researching more suitable and efficient antennas for medical applications.

Spatial group delay patterns for three ultra wideband spline antennas

The IEEE ultra wideband (UWB) standard includes both a multiple frequency carrier (MB-OFDM) and an impulse spectrum (DS-UWB) method, for which application antennas should be appropriately optimized. Small printed monopoles with outline features that can be defined by a Bezier-spline [1] have good matched impedance performance across the 3.1 - 10.6 GHz band. For communications applications, an omni-directional pattern, where the gain pattern varies by less than plusmn5 dBi, and a stable frequency-gain profile in the azimuth plane, allow for an even spatial coverage in all directions. In the case of an impulse system, any non-linear phase transfer performance in the antenna adds distortion to the transieved pulses therefore reducing the data rates. Contemporary UWB antenna gain performances are often presented across the whole spectrum using contour plots. This discloses more details and compliments the conventional sampled frequency polar plots that are more suited to narrow bandwidth antennas. In this paper, the approach is extended to a group delay pattern measurement which is more comprehensive than the traditional and limited boresight-only approach.

Interaction of RF-Hyperthermia applicator with high fidelity human body model

A compact patch antenna working at the 434 MHz ISM frequency band is proposed as an RF-Hyperthermia applicator. The electromagnetic interaction in terms of S11, SAR and E-Field distribution of the antenna with a High Fidelity human body model is investigated. This analysis provides useful information for engineers and clinical staff to develop more efficient and smaller antennas for medical applications, in particular for RF-Hyperthermia cancer therapy, where the size of the antenna determines tumor accessibility.

A stable near-field antenna hyperthermia applicator for various tissue types and topologies

In an expanding number of worldwide clinical trials, conventional loop, dipole and square-patch antennas perform as external hyperthermia applicators for the adjunct treatment of cancer cells at superficial depths inside the human body. A smaller patch design in very close proximity with various phantom tissue models produces focused specific absorption rate (SAR) patterns without significant frequency detuning or impedance mismatch. Synthesized treatment conditions for different body phantoms suggest that the SAR profile of the compact antenna is stable for a range of tissue types and topologies. This paper will describe the miniaturisation and tissue coupling design characteristics for the near-field antenna applicator. Performance metrics are indicated with impedance matching, SAR and thermal profiles.