A. Martellosio

Dielectric Properties Characterization From 0.5 to 50 GHz of Breast Cancer Tissues

Knowledge of the dielectric properties of human tissues is important for several biomedical applications, including imaging and hyperthermia treatment, as well as for determining safety thresholds in policy making. Breast tissues, both normal and tumorous, are of particular interest because of the medical and social impact of breast cancers. While experimental data is available up to 20 GHz, for higher frequencies, this information is missing, or has been extrapolated from models based on lower-frequency data. Emerging technologies and applications in the millimeter-wave region would benefit from experimental data that bridge this gap. This paper presents the characterization of dielectric properties of breast tissues for the frequency range from 0.5 to 50 GHz. Cole–Cole models are derived for normal and tumorous tissues based on experimental measurements on more than 220 tissue samples obtained at surgery (ex vivo) from a population exceeding 50 patients, covering a wide span of normal and tumorous tissues, from patients ranging in age from 28 to 85 years, with a time from excision to measurements under 3.5 h. This paper also presents a comprehensive analysis of the differences between normal and tumorous breast tissues at different frequencies in terms of sensitivity and specificity.

A novel band-pass filter based on a periodically drilled SIW structure

The design and fabrication of a band-pass step impedance filter based on high and low dielectric constant sections has been realized on substrate integrated waveguide (SIW) technology. The overall process includes the design of the ideal band-pass prototype filter, where the implementation of the impedance inverters has been carried out by means of waveguide sections of lower permittivity. This can be practically achieved by implementing arrays of air holes along the waveguide. Several SIW structures with and without arrays of air holes have been simulated and fabricated in order to experimentally evaluate their relative permittivity. Additionally, the equivalent filter in SIW technology has been designed and optimized. Finally, a prototype of the designed filter has been fabricated and measured, showing a good agreement between measurements and simulations, which demonstrates the validity of the proposed design approach.

On the Feasibility of Breast Cancer Imaging Systems at Millimeter-Waves Frequencies

Medical imaging currently relies on several techniques, including X-rays, magnetic resonance, and echography. However, these techniques exhibit drawbacks, and alternative approaches are required. Microwave imaging has been proposed as a possible solution, especially for breast cancer imaging. However, most of these systems work with a central frequency of a few gigahertz, and this leads to a suboptimum resolution, which can jeopardize the image quality. Millimeter waves can provide superior resolutions, at the cost of a lower penetration depth within the breast tissue. In addition, a significant fraction of the power generated by a mm-wave imaging system would be reflected back from the skin. For these reasons, and also considering that mm-wave transmitters and receivers have been historically outperformed by microwave counterparts in terms of available power and sensitivity, mm-wave imaging has not been considered a possible solution. This paper contributes to demonstrate a paradigm shift toward the possible use of mm-waves for breast cancer imaging of targets a few centimeter below the skin, a useful penetration depth for several cases. All key points are addressed using analytical, full-wave, and multiphysics simulations, including the system architecture (linear and conformal), the safety aspects (power density, specific absorption rate, and temperature increase), and the use of realistic breast models derived from ex vivo measurements.

RF analysis at K band of a radome-covered ground station at polar latitudes

X-band for Earth Observation (EO) is becoming very congested and this aspect induced the International Telecommunication Union (ITU) to reorganize the frequency allocations in use. The allocation of the 26-GHz band (i.e. 25.5 to 27 GHz) for the downlink, available for the first time for EO applications, allows for collecting a large amount of data. However, considering that several EO missions fly along polar orbits, a ground station (GS) installed at polar latitudes, where high-speed winds, low temperatures and precipitations particularly austere are normal, is fundamental to exploit all the satellite passages. For this reason, the use of radome structures to protect the GS against the environmental conditions is mandatory. This paper addresses the exploitation of the 26-GHz band for future EO satellites, namely the NASA/NOAA JPSS-1 satellite and the EUMETSAT Metop-SG satellite, with specific regard to the RF analysis, of European Space Agency (ESA) GS to be installed in Svalbard. In particular, since the use of the 26-GHz band for GSs located at polar latitudes is a complete novelty, special attention is paid to the G/T analysis and the radome performance.

High-Frequency Radomes for Polar Region Ground Stations: The State of the Art and Novel Developments of Radome Technologies

Satellite communications with the ability to provide a downlink channel with high bit rates are needed, and this need is driving frequency upscaling toward bands higher than the X band. A number of these satellites requires ground stations at the polar region, which are usually protected against the harsh environment using radomes.